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Groups > linux.kernel > #1346683 > unrolled thread

Re: [PATCH] usbhid: Fix lockdep unannotated irqs-off warning

Started bySteven Rostedt <rostedt@goodmis.org>
First post2016-03-01 16:10 +0100
Last post2016-03-02 18:00 +0100
Articles 10 — 3 participants

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  Re: [PATCH] usbhid: Fix lockdep unannotated irqs-off warning Steven Rostedt <rostedt@goodmis.org> - 2016-03-01 16:10 +0100
    Re: [PATCH] usbhid: Fix lockdep unannotated irqs-off warning Peter Zijlstra <peterz@infradead.org> - 2016-03-01 16:20 +0100
      Re: [PATCH] usbhid: Fix lockdep unannotated irqs-off warning Sedat Dilek <sedat.dilek@gmail.com> - 2016-03-02 16:10 +0100
        Re: [PATCH] usbhid: Fix lockdep unannotated irqs-off warning Peter Zijlstra <peterz@infradead.org> - 2016-03-02 16:20 +0100
          Re: [PATCH] usbhid: Fix lockdep unannotated irqs-off warning Steven Rostedt <rostedt@goodmis.org> - 2016-03-02 17:00 +0100
          Re: [PATCH] usbhid: Fix lockdep unannotated irqs-off warning Peter Zijlstra <peterz@infradead.org> - 2016-03-02 17:30 +0100
            Re: [PATCH] usbhid: Fix lockdep unannotated irqs-off warning Steven Rostedt <rostedt@goodmis.org> - 2016-03-02 17:40 +0100
              Re: [PATCH] usbhid: Fix lockdep unannotated irqs-off warning Peter Zijlstra <peterz@infradead.org> - 2016-03-02 17:50 +0100
            Re: [PATCH] usbhid: Fix lockdep unannotated irqs-off warning Sedat Dilek <sedat.dilek@gmail.com> - 2016-03-02 17:50 +0100
              Re: [PATCH] usbhid: Fix lockdep unannotated irqs-off warning Sedat Dilek <sedat.dilek@gmail.com> - 2016-03-02 18:00 +0100

#1346683 — Re: [PATCH] usbhid: Fix lockdep unannotated irqs-off warning

FromSteven Rostedt <rostedt@goodmis.org>
Date2016-03-01 16:10 +0100
SubjectRe: [PATCH] usbhid: Fix lockdep unannotated irqs-off warning
Message-ID<r7U5Y-2ju-25@gated-at.bofh.it>
On Tue, 1 Mar 2016 11:05:42 +0100
Sedat Dilek <sedat.dilek@gmail.com> wrote:


> [ FACT #3: TEST-CASE #2 ]
> 
> The most reliable test-case is to simply unplug my external Logitech
> USB mouse - saw this by accident.
> YES, it was so simple.

Just to clarify, this happens on gcc and clang?


> 
> --- dmesg_4.5.0-rc6-2-llvmlinux-amd64.txt       2016-02-29
> 21:23:56.399691975 +0100
> +++ dmesg_4.5.0-rc6-2-llvmlinux-amd64_usbmouse-unplugged.txt
> 2016-02-29 21:28:14.401832240 +0100
> @@ -832,3 +832,75 @@
>  [   66.529779] PPP BSD Compression module registered
>  [   66.563013] PPP Deflate Compression module registered
>  [   66.978977] usb 2-1.5: USB disconnect, device number 4
> +[  321.937369] usb 2-1.4: USB disconnect, device number 3
> +[  321.950810] BUG: sleeping function called from invalid context at
> kernel/workqueue.c:2785
> +[  321.950816] in_atomic(): 0, irqs_disabled(): 1, pid: 44, name: kworker/2:1
> +[  321.950819] 9 locks held by kworker/2:1/44:
> +[  321.950820]  #0:  ("usb_hub_wq"){.+.+.+}, at: [<ffffffff810a7c5f>]
> process_one_work+0x30f/0x8d0
> +[  321.950830]  #1:  ((&hub->events)){+.+.+.}, at:
> [<ffffffff810a7c8c>] process_one_work+0x33c/0x8d0
> +[  321.950836]  #2:  (&dev->mutex){......}, at: [<ffffffff816fb0e0>]
> hub_event+0x50/0x15b0
> +[  321.950844]  #3:  (&dev->mutex){......}, at: [<ffffffff816f686f>]
> usb_disconnect+0x5f/0x2c0
> +[  321.950849]  #4:  (&dev->mutex){......}, at: [<ffffffff816245a2>]
> device_release_driver+0x22/0x40
> +[  321.950856]  #5:  (&dev->mutex){......}, at: [<ffffffff816245a2>]
> device_release_driver+0x22/0x40
> +[  321.950862]  #6:  (input_mutex){+.+.+.}, at: [<ffffffff8175171a>]
> __input_unregister_device+0x9a/0x190
> +[  321.950869]  #7:  (&dev->mutex#2){+.+...}, at:
> [<ffffffff8174fe27>] input_close_device+0x27/0x70
> +[  321.950875]  #8:  (hid_open_mut){+.+...}, at: [<ffffffffa0057388>]
> usbhid_close+0x28/0xb0 [usbhid]
> +[  321.950883] irq event stamp: 47770
> +[  321.950885] hardirqs last  enabled at (47769):
> [<ffffffff819426a2>] _raw_spin_unlock_irq+0x32/0x60
> +[  321.950889] hardirqs last disabled at (47770):
> [<ffffffff81115bdc>] del_timer_sync+0x3c/0x110

According to lockdep, interrupts were last disabled in del_timer_sync,
and they were never enabled. The numbers in parenthesis show the order
of events. _raw_spin_unlock_irq() at 47769, then del_timer_sync at
47770.

But why did they not get enabled again? We have:

	local_irq_save(flags);
	lock_map_acquire(&timer->lockdep_map);
	lock_map_release(&timer->lockdep_map);
	local_irq_restore(flags);

If this caused an issue, then you would have a lockdep splat. But
perhaps something corrupted "flags", and interrupts were not re-enabled?

> +[  321.950894] softirqs last  enabled at (47112):
> [<ffffffff810871a2>] __do_softirq+0x5a2/0x610
> +[  321.950898] softirqs last disabled at (47097):
> [<ffffffff8108747c>] irq_exit+0x9c/0x120
> +[  321.950903] CPU: 2 PID: 44 Comm: kworker/2:1 Not tainted
> 4.5.0-rc6-2-llvmlinux-amd64 #1
> +[  321.950905] Hardware name: SAMSUNG ELECTRONICS CO., LTD.
> 530U3BI/530U4BI/530U4BH/530U3BI/530U4BI/530U4BH, BIOS 13XK 03/28/2013
> +[  321.950908] Workqueue: usb_hub_wq hub_event
> +[  321.950911]  ffff8800d3326948 0000000000000092 0000000000000000
> ffff8800d4347568
> +[  321.950915]  ffffffff814ba7d4 ffff8800d43474f8 ffff8800d4340cc0
> ffff8800d4347568
> +[  321.950919]  ffffffff810e28fd 0000000000000092 0000000000000096
> ffff8800d43475a8
> +[  321.950923] Call Trace:
> +[  321.950927]  [<ffffffff814ba7d4>] dump_stack+0xa4/0xf0
> +[  321.950931]  [<ffffffff810e28fd>] ? print_irqtrace_events+0xcd/0xe0
> +[  321.950936]  [<ffffffff810bf495>] ___might_sleep+0x295/0x2b0
> +[  321.950939]  [<ffffffff810bf18f>] __might_sleep+0x4f/0xc0

This triggered on the might_sleep() in start_flush_work() because
something left interrupts enable.

Just strange.

-- Steve


> +[  321.950943]  [<ffffffff810a12ef>] start_flush_work+0x2f/0x2a0
> +[  321.950946]  [<ffffffff810a129c>] flush_work+0x5c/0x80
> +[  321.950949]  [<ffffffff810a125a>] ? flush_work+0x1a/0x80
> +[  321.950953]  [<ffffffff810e247d>] ? trace_hardirqs_off+0xd/0x10
> +[  321.950956]  [<ffffffff810a032a>] ? try_to_grab_pending+0x4a/0x260
> +[  321.950960]  [<ffffffff810a1717>] __cancel_work_timer+0x197/0x290
> +[  321.950963]  [<ffffffff81115b8d>] ? try_to_del_timer_sync+0xad/0xc0
> +[  321.950966]  [<ffffffff810a1578>] cancel_work_sync+0x18/0x20
> +[  321.950970]  [<ffffffffa00573d5>] usbhid_close+0x75/0xb0 [usbhid]
> +[  321.950977]  [<ffffffffa003a481>] hidinput_close+0x31/0x40 [hid]
> +[  321.950982]  [<ffffffffa003a450>] ? hidinput_open+0x40/0x40 [hid]
> +[  321.950985]  [<ffffffff8174fe48>] input_close_device+0x48/0x70
> +[  321.950988]  [<ffffffff81757f85>] evdev_cleanup+0xd5/0xe0
> +[  321.950990]  [<ffffffff81757b0c>] evdev_disconnect+0x2c/0x60
> +[  321.950993]  [<ffffffff8175173e>] __input_unregister_device+0xbe/0x190
> +[  321.950996]  [<ffffffff8175164a>] input_unregister_device+0x4a/0x80
> +[  321.951001]  [<ffffffffa003a29f>] hidinput_disconnect+0x8f/0xc0 [hid]
> +[  321.951007]  [<ffffffffa0034a30>] hid_device_remove+0xb0/0x130 [hid]
> +[  321.951010]  [<ffffffff816246bd>] __device_release_driver+0xfd/0x190
> +[  321.951014]  [<ffffffff816245aa>] device_release_driver+0x2a/0x40
> +[  321.951017]  [<ffffffff816224a3>] bus_remove_device+0x153/0x190
> +[  321.951020]  [<ffffffff8161f5fb>] device_del+0x1db/0x2b0
> +[  321.951025]  [<ffffffffa0033c1c>] hid_destroy_device+0x2c/0x60 [hid]
> +[  321.951029]  [<ffffffffa0058537>] usbhid_disconnect+0x67/0x90 [usbhid]
> +[  321.951033]  [<ffffffff81706ebf>] usb_unbind_interface+0xbf/0x2b0
> +[  321.951037]  [<ffffffff816246bd>] __device_release_driver+0xfd/0x190
> +[  321.951040]  [<ffffffff816245aa>] device_release_driver+0x2a/0x40
> +[  321.951043]  [<ffffffff816224a3>] bus_remove_device+0x153/0x190
> +[  321.951046]  [<ffffffff8161f5fb>] device_del+0x1db/0x2b0
> +[  321.951048]  [<ffffffff8161f6fc>] ? device_unregister+0x2c/0x40
> +[  321.951051]  [<ffffffff81704f6b>] usb_disable_device+0x10b/0x3b0
> +[  321.951054]  [<ffffffff816f6904>] usb_disconnect+0xf4/0x2c0
> +[  321.951057]  [<ffffffff816fbc3d>] hub_event+0xbad/0x15b0
> +[  321.951060]  [<ffffffff819426a2>] ? _raw_spin_unlock_irq+0x32/0x60
> +[  321.951063]  [<ffffffff810a7e0e>] process_one_work+0x4be/0x8d0
> +[  321.951065]  [<ffffffff810a7c8c>] ? process_one_work+0x33c/0x8d0
> +[  321.951068]  [<ffffffff810a757b>] worker_thread+0x5cb/0x750
> +[  321.951071]  [<ffffffff810a6fb0>] ? destroy_worker+0x110/0x110
> +[  321.951074]  [<ffffffff810ae1c5>] kthread+0x115/0x120
> +[  321.951077]  [<ffffffff810e248d>] ? trace_hardirqs_on+0xd/0x10
> +[  321.951080]  [<ffffffff810ae0b0>] ? flush_kthread_worker+0x80/0x80
> +[  321.951084]  [<ffffffff819435ff>] ret_from_fork+0x3f/0x70
> +[  321.951087]  [<ffffffff810ae0b0>] ? flush_kthread_worker+0x80/0x80
>

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#1346687

FromPeter Zijlstra <peterz@infradead.org>
Date2016-03-01 16:20 +0100
Message-ID<r7UfE-2na-11@gated-at.bofh.it>
In reply to#1346683
On Tue, Mar 01, 2016 at 10:07:40AM -0500, Steven Rostedt wrote:
> On Tue, 1 Mar 2016 11:05:42 +0100
> Sedat Dilek <sedat.dilek@gmail.com> wrote:
> 
> 
> > [ FACT #3: TEST-CASE #2 ]
> > 
> > The most reliable test-case is to simply unplug my external Logitech
> > USB mouse - saw this by accident.
> > YES, it was so simple.
> 
> Just to clarify, this happens on gcc and clang?

Just clang from what I gather.

> > --- dmesg_4.5.0-rc6-2-llvmlinux-amd64.txt       2016-02-29
> > 21:23:56.399691975 +0100
> > +++ dmesg_4.5.0-rc6-2-llvmlinux-amd64_usbmouse-unplugged.txt
> > 2016-02-29 21:28:14.401832240 +0100
> > @@ -832,3 +832,75 @@
> >  [   66.529779] PPP BSD Compression module registered
> >  [   66.563013] PPP Deflate Compression module registered
> >  [   66.978977] usb 2-1.5: USB disconnect, device number 4
> > +[  321.937369] usb 2-1.4: USB disconnect, device number 3
> > +[  321.950810] BUG: sleeping function called from invalid context at
> > kernel/workqueue.c:2785
> > +[  321.950816] in_atomic(): 0, irqs_disabled(): 1, pid: 44, name: kworker/2:1
> > +[  321.950819] 9 locks held by kworker/2:1/44:
> > +[  321.950820]  #0:  ("usb_hub_wq"){.+.+.+}, at: [<ffffffff810a7c5f>]
> > process_one_work+0x30f/0x8d0
> > +[  321.950830]  #1:  ((&hub->events)){+.+.+.}, at:
> > [<ffffffff810a7c8c>] process_one_work+0x33c/0x8d0
> > +[  321.950836]  #2:  (&dev->mutex){......}, at: [<ffffffff816fb0e0>]
> > hub_event+0x50/0x15b0
> > +[  321.950844]  #3:  (&dev->mutex){......}, at: [<ffffffff816f686f>]
> > usb_disconnect+0x5f/0x2c0
> > +[  321.950849]  #4:  (&dev->mutex){......}, at: [<ffffffff816245a2>]
> > device_release_driver+0x22/0x40
> > +[  321.950856]  #5:  (&dev->mutex){......}, at: [<ffffffff816245a2>]
> > device_release_driver+0x22/0x40
> > +[  321.950862]  #6:  (input_mutex){+.+.+.}, at: [<ffffffff8175171a>]
> > __input_unregister_device+0x9a/0x190
> > +[  321.950869]  #7:  (&dev->mutex#2){+.+...}, at:
> > [<ffffffff8174fe27>] input_close_device+0x27/0x70
> > +[  321.950875]  #8:  (hid_open_mut){+.+...}, at: [<ffffffffa0057388>]
> > usbhid_close+0x28/0xb0 [usbhid]
> > +[  321.950883] irq event stamp: 47770
> > +[  321.950885] hardirqs last  enabled at (47769):
> > [<ffffffff819426a2>] _raw_spin_unlock_irq+0x32/0x60
> > +[  321.950889] hardirqs last disabled at (47770):
> > [<ffffffff81115bdc>] del_timer_sync+0x3c/0x110
> 
> According to lockdep, interrupts were last disabled in del_timer_sync,
> and they were never enabled. The numbers in parenthesis show the order
> of events. _raw_spin_unlock_irq() at 47769, then del_timer_sync at
> 47770.
> 
> But why did they not get enabled again? We have:
> 
> 	local_irq_save(flags);
> 	lock_map_acquire(&timer->lockdep_map);
> 	lock_map_release(&timer->lockdep_map);
> 	local_irq_restore(flags);
> 
> If this caused an issue, then you would have a lockdep splat. But
> perhaps something corrupted "flags", and interrupts were not re-enabled?

Right, most odd. Sedat, could you provide objdump -D of the relevant
sections of vmlinux ?

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#1348115

FromSedat Dilek <sedat.dilek@gmail.com>
Date2016-03-02 16:10 +0100
Message-ID<r8gzw-UO-21@gated-at.bofh.it>
In reply to#1346687
On 3/1/16, Peter Zijlstra <peterz@infradead.org> wrote:
> On Tue, Mar 01, 2016 at 10:07:40AM -0500, Steven Rostedt wrote:
>> On Tue, 1 Mar 2016 11:05:42 +0100
>> Sedat Dilek <sedat.dilek@gmail.com> wrote:
>>
>>
>> > [ FACT #3: TEST-CASE #2 ]
>> >
>> > The most reliable test-case is to simply unplug my external Logitech
>> > USB mouse - saw this by accident.
>> > YES, it was so simple.
>>
>> Just to clarify, this happens on gcc and clang?
>
> Just clang from what I gather.
>

YES, gcc, but I can crash my Xorg, but do not see a pile of nothing in
my dmesg-log.

>> > --- dmesg_4.5.0-rc6-2-llvmlinux-amd64.txt       2016-02-29
>> > 21:23:56.399691975 +0100
>> > +++ dmesg_4.5.0-rc6-2-llvmlinux-amd64_usbmouse-unplugged.txt
>> > 2016-02-29 21:28:14.401832240 +0100
>> > @@ -832,3 +832,75 @@
>> >  [   66.529779] PPP BSD Compression module registered
>> >  [   66.563013] PPP Deflate Compression module registered
>> >  [   66.978977] usb 2-1.5: USB disconnect, device number 4
>> > +[  321.937369] usb 2-1.4: USB disconnect, device number 3
>> > +[  321.950810] BUG: sleeping function called from invalid context at
>> > kernel/workqueue.c:2785
>> > +[  321.950816] in_atomic(): 0, irqs_disabled(): 1, pid: 44, name:
>> > kworker/2:1
>> > +[  321.950819] 9 locks held by kworker/2:1/44:
>> > +[  321.950820]  #0:  ("usb_hub_wq"){.+.+.+}, at: [<ffffffff810a7c5f>]
>> > process_one_work+0x30f/0x8d0
>> > +[  321.950830]  #1:  ((&hub->events)){+.+.+.}, at:
>> > [<ffffffff810a7c8c>] process_one_work+0x33c/0x8d0
>> > +[  321.950836]  #2:  (&dev->mutex){......}, at: [<ffffffff816fb0e0>]
>> > hub_event+0x50/0x15b0
>> > +[  321.950844]  #3:  (&dev->mutex){......}, at: [<ffffffff816f686f>]
>> > usb_disconnect+0x5f/0x2c0
>> > +[  321.950849]  #4:  (&dev->mutex){......}, at: [<ffffffff816245a2>]
>> > device_release_driver+0x22/0x40
>> > +[  321.950856]  #5:  (&dev->mutex){......}, at: [<ffffffff816245a2>]
>> > device_release_driver+0x22/0x40
>> > +[  321.950862]  #6:  (input_mutex){+.+.+.}, at: [<ffffffff8175171a>]
>> > __input_unregister_device+0x9a/0x190
>> > +[  321.950869]  #7:  (&dev->mutex#2){+.+...}, at:
>> > [<ffffffff8174fe27>] input_close_device+0x27/0x70
>> > +[  321.950875]  #8:  (hid_open_mut){+.+...}, at: [<ffffffffa0057388>]
>> > usbhid_close+0x28/0xb0 [usbhid]
>> > +[  321.950883] irq event stamp: 47770
>> > +[  321.950885] hardirqs last  enabled at (47769):
>> > [<ffffffff819426a2>] _raw_spin_unlock_irq+0x32/0x60
>> > +[  321.950889] hardirqs last disabled at (47770):
>> > [<ffffffff81115bdc>] del_timer_sync+0x3c/0x110
>>
>> According to lockdep, interrupts were last disabled in del_timer_sync,
>> and they were never enabled. The numbers in parenthesis show the order
>> of events. _raw_spin_unlock_irq() at 47769, then del_timer_sync at
>> 47770.
>>
>> But why did they not get enabled again? We have:
>>
>> 	local_irq_save(flags);
>> 	lock_map_acquire(&timer->lockdep_map);
>> 	lock_map_release(&timer->lockdep_map);
>> 	local_irq_restore(flags);
>>
>> If this caused an issue, then you would have a lockdep splat. But
>> perhaps something corrupted "flags", and interrupts were not re-enabled?
>
> Right, most odd. Sedat, could you provide objdump -D of the relevant
> sections of vmlinux ?
>

Can you give some clear instructions - for what shall I look for in special?

I can send you a 300MiB mail-bomb if you like :-).

$ cd linux-git
$ objdump -D vmlinux > ../objdump-D_vmlinux.txt
$ du -m ../objdump-D_vmlinux.txt
294     ../objdump-D_vmlinux.txt

I have now built with the same kernel-config for gcc and clang and
archived the most interesting stuff.
Before sending the stuff out, I would like to have some clear instructions.

Thanks.

- Sedat -

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#1348128

FromPeter Zijlstra <peterz@infradead.org>
Date2016-03-02 16:20 +0100
Message-ID<r8gJc-Yz-25@gated-at.bofh.it>
In reply to#1348115
On Wed, Mar 02, 2016 at 04:00:49PM +0100, Sedat Dilek wrote:
> >
> > Right, most odd. Sedat, could you provide objdump -D of the relevant
> > sections of vmlinux ?
> >
> 
> Can you give some clear instructions - for what shall I look for in special?

objdump -D vmlinux | awk '/<[^>]*>:$/ { p=0; } /<del_timer_sync>:/ { p=1; } { if (p) print $0; }'

might be a good start, esp. if the output differs between the LLVM and
GCC cases (+- address muck).

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#1348238

FromSteven Rostedt <rostedt@goodmis.org>
Date2016-03-02 17:00 +0100
Message-ID<r8hlW-1fW-51@gated-at.bofh.it>
In reply to#1348128
[ Resend with reply all, instead of just "reply" ]

On Wed, 2 Mar 2016 16:53:36 +0100
Sedat Dilek <sedat.dilek@gmail.com> wrote:

> ffffffff8110f3f0 <del_timer>:
> ffffffff8110f3f0:	55                   	push   %rbp
> ffffffff8110f3f1:	48 89 e5             	mov    %rsp,%rbp
> ffffffff8110f3f4:	41 57                	push   %r15
> ffffffff8110f3f6:	41 56                	push   %r14
> ffffffff8110f3f8:	53                   	push   %rbx
> ffffffff8110f3f9:	50                   	push   %rax
> ffffffff8110f3fa:	48 89 fb             	mov    %rdi,%rbx
> ffffffff8110f3fd:	e8 ee 6f 80 00       	callq  ffffffff819163f0 <mcount>
> ffffffff8110f402:	e8 e9 6f 80 00       	callq  ffffffff819163f0 <mcount>
> ffffffff8110f407:	e8 e4 6f 80 00       	callq  ffffffff819163f0 <mcount>
> ffffffff8110f40c:	e8 df 6f 80 00       	callq  ffffffff819163f0 <mcount>

What is this about?

-- Steve

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#1348298

FromPeter Zijlstra <peterz@infradead.org>
Date2016-03-02 17:30 +0100
Message-ID<r8hOW-1I2-9@gated-at.bofh.it>
In reply to#1348128
On Wed, Mar 02, 2016 at 04:53:36PM +0100, Sedat Dilek wrote:
> ffffffff8110f570 <del_timer_sync>:
> ffffffff8110f570:	55                   	push   %rbp
> ffffffff8110f571:	48 89 e5             	mov    %rsp,%rbp
> ffffffff8110f574:	41 57                	push   %r15
> ffffffff8110f576:	41 56                	push   %r14
> ffffffff8110f578:	53                   	push   %rbx
> ffffffff8110f579:	48 83 ec 28          	sub    $0x28,%rsp

stack offset is 0x28 bytes [*]

> ffffffff8110f57d:	48 89 fb             	mov    %rdi,%rbx
> ffffffff8110f580:	e8 6b 6e 80 00       	callq  ffffffff819163f0 <mcount>
> ffffffff8110f585:	e8 66 6e 80 00       	callq  ffffffff819163f0 <mcount>
> ffffffff8110f58a:	e8 61 6e 80 00       	callq  ffffffff819163f0 <mcount>
> ffffffff8110f58f:	e8 5c 6e 80 00       	callq  ffffffff819163f0 <mcount>

Your compiler is on drugs!

> ffffffff8110f594:	9c                   	pushfq 
> ffffffff8110f595:	8f 45 e0             	popq   -0x20(%rbp)

Saves flags in -0x20(%rbp)

> ffffffff8110f598:	4c 8b 7d e0          	mov    -0x20(%rbp),%r15

And in %r15

/me wonders what's wrong with: popf %r15

> ffffffff8110f59c:	e8 4f 6e 80 00       	callq  ffffffff819163f0 <mcount>
> ffffffff8110f5a1:	e8 4a 6e 80 00       	callq  ffffffff819163f0 <mcount>
> ffffffff8110f5a6:	fa                   	cli    
> ffffffff8110f5a7:	e8 84 cb fc ff       	callq  ffffffff810dc130 <trace_hardirqs_off>
> ffffffff8110f5ac:	4c 8d 73 50          	lea    0x50(%rbx),%r14
> ffffffff8110f5b0:	48 c7 04 24 b0 f5 10 	movq   $0xffffffff8110f5b0,(%rsp)
> ffffffff8110f5b7:	81 
> ffffffff8110f5b8:	31 f6                	xor    %esi,%esi
> ffffffff8110f5ba:	31 d2                	xor    %edx,%edx
> ffffffff8110f5bc:	31 c9                	xor    %ecx,%ecx
> ffffffff8110f5be:	41 b8 01 00 00 00    	mov    $0x1,%r8d
> ffffffff8110f5c4:	45 31 c9             	xor    %r9d,%r9d
> ffffffff8110f5c7:	4c 89 f7             	mov    %r14,%rdi
> ffffffff8110f5ca:	e8 c1 e5 fc ff       	callq  ffffffff810ddb90 <lock_acquire>
> ffffffff8110f5cf:	be 01 00 00 00       	mov    $0x1,%esi
> ffffffff8110f5d4:	48 c7 c2 cf f5 10 81 	mov    $0xffffffff8110f5cf,%rdx
> ffffffff8110f5db:	4c 89 f7             	mov    %r14,%rdi
> ffffffff8110f5de:	e8 8d 08 fd ff       	callq  ffffffff810dfe70 <lock_release>
> ffffffff8110f5e3:	e8 08 6e 80 00       	callq  ffffffff819163f0 <mcount>

> ffffffff8110f5e8:	4c 89 f8             	mov    %r15,%rax
> ffffffff8110f5eb:	49 89 c6             	mov    %rax,%r14

Moves r15 into r14 through rax


> ffffffff8110f5ee:	f6 c4 02             	test   $0x2,%ah
> ffffffff8110f5f1:	75 19                	jne    ffffffff8110f60c <del_timer_sync+0x9c>
> ffffffff8110f5f3:	e8 f8 6d 80 00       	callq  ffffffff819163f0 <mcount>
> ffffffff8110f5f8:	e8 f3 6d 80 00       	callq  ffffffff819163f0 <mcount>


> ffffffff8110f5fd:	4c 89 75 d0          	mov    %r14,-0x30(%rbp)
> ffffffff8110f601:	ff 75 d0             	pushq  -0x30(%rbp)
> ffffffff8110f604:	9d                   	popfq  

put r14 into -0x30(rbp) and pushes/pops that, see [*] this is 8 bytes
over stack ?!

> ffffffff8110f605:	e8 26 cb fc ff       	callq  ffffffff810dc130 <trace_hardirqs_off>
> ffffffff8110f60a:	eb 17                	jmp    ffffffff8110f623 <del_timer_sync+0xb3>
> ffffffff8110f60c:	e8 2f cb fc ff       	callq  ffffffff810dc140 <trace_hardirqs_on>
> ffffffff8110f611:	e8 da 6d 80 00       	callq  ffffffff819163f0 <mcount>
> ffffffff8110f616:	e8 d5 6d 80 00       	callq  ffffffff819163f0 <mcount>
> ffffffff8110f61b:	4c 89 75 d8          	mov    %r14,-0x28(%rbp)
> ffffffff8110f61f:	ff 75 d8             	pushq  -0x28(%rbp)
> ffffffff8110f622:	9d                   	popfq  

puts r14 into -0x28(rbp) and pushes/pops that

> ffffffff8110f623:	e8 c8 6d 80 00       	callq  ffffffff819163f0 <mcount>
> ffffffff8110f628:	65 8b 04 25 d4 ae 00 	mov    %gs:0xaed4,%eax
> ffffffff8110f62f:	00 
> ffffffff8110f630:	a9 00 00 0f 00       	test   $0xf0000,%eax
> ffffffff8110f635:	74 25                	je     ffffffff8110f65c <del_timer_sync+0xec>
> ffffffff8110f637:	f6 43 2a 20          	testb  $0x20,0x2a(%rbx)
> ffffffff8110f63b:	75 1f                	jne    ffffffff8110f65c <del_timer_sync+0xec>
> ffffffff8110f63d:	48 c7 c7 04 54 c5 81 	mov    $0xffffffff81c55404,%rdi
> ffffffff8110f644:	be 61 04 00 00       	mov    $0x461,%esi
> ffffffff8110f649:	e8 12 c4 f6 ff       	callq  ffffffff8107ba60 <warn_slowpath_null>
> ffffffff8110f64e:	eb 0c                	jmp    ffffffff8110f65c <del_timer_sync+0xec>
> ffffffff8110f650:	e8 9b 6d 80 00       	callq  ffffffff819163f0 <mcount>
> ffffffff8110f655:	e8 96 6d 80 00       	callq  ffffffff819163f0 <mcount>
> ffffffff8110f65a:	f3 90                	pause  
> ffffffff8110f65c:	48 89 df             	mov    %rbx,%rdi
> ffffffff8110f65f:	e8 4c fe ff ff       	callq  ffffffff8110f4b0 <try_to_del_timer_sync>
> ffffffff8110f664:	85 c0                	test   %eax,%eax
> ffffffff8110f666:	78 e8                	js     ffffffff8110f650 <del_timer_sync+0xe0>
> ffffffff8110f668:	48 83 c4 28          	add    $0x28,%rsp
> ffffffff8110f66c:	5b                   	pop    %rbx
> ffffffff8110f66d:	41 5e                	pop    %r14
> ffffffff8110f66f:	41 5f                	pop    %r15
> ffffffff8110f671:	5d                   	pop    %rbp
> ffffffff8110f672:	c3                   	retq   
> ffffffff8110f673:	66 66 66 66 2e 0f 1f 	data32 data32 data32 nopw %cs:0x0(%rax,%rax,1)
> ffffffff8110f67a:	84 00 00 00 00 00 


That LLVM generate disgusting code, as a contrast, this is what my GCC
makes of this:

ffffffff81155f50 <del_timer_sync>:
ffffffff81155f50:       e8 bb 02 9c 00          callq  ffffffff81b16210 <__fentry__>
ffffffff81155f55:       55                      push   %rbp
ffffffff81155f56:       48 89 e5                mov    %rsp,%rbp
ffffffff81155f59:       41 55                   push   %r13
ffffffff81155f5b:       41 54                   push   %r12
ffffffff81155f5d:       53                      push   %rbx
ffffffff81155f5e:       48 89 fb                mov    %rdi,%rbx
ffffffff81155f61:       48 83 ec 08             sub    $0x8,%rsp
ffffffff81155f65:       9c                      pushfq 
ffffffff81155f66:       41 5c                   pop    %r12
ffffffff81155f68:       fa                      cli    
ffffffff81155f69:       e8 72 5c fd ff          callq  ffffffff8112bbe0 <trace_hardirqs_off>
ffffffff81155f6e:       4c 8d 6b 50             lea    0x50(%rbx),%r13
ffffffff81155f72:       45 31 c9                xor    %r9d,%r9d
ffffffff81155f75:       31 c9                   xor    %ecx,%ecx
ffffffff81155f77:       31 d2                   xor    %edx,%edx
ffffffff81155f79:       31 f6                   xor    %esi,%esi
ffffffff81155f7b:       4c 89 ef                mov    %r13,%rdi
ffffffff81155f7e:       48 c7 04 24 55 5f 15    movq   $0xffffffff81155f55,(%rsp)
ffffffff81155f85:       81 
ffffffff81155f86:       41 b8 01 00 00 00       mov    $0x1,%r8d
ffffffff81155f8c:       e8 3f b3 fd ff          callq  ffffffff811312d0 <lock_acquire>
ffffffff81155f91:       48 c7 c2 55 5f 15 81    mov    $0xffffffff81155f55,%rdx
ffffffff81155f98:       be 01 00 00 00          mov    $0x1,%esi
ffffffff81155f9d:       4c 89 ef                mov    %r13,%rdi
ffffffff81155fa0:       e8 0b b5 fd ff          callq  ffffffff811314b0 <lock_release>
ffffffff81155fa5:       41 f7 c4 00 02 00 00    test   $0x200,%r12d
ffffffff81155fac:       75 52                   jne    ffffffff81156000 <del_timer_sync+0xb0>
ffffffff81155fae:       41 54                   push   %r12
ffffffff81155fb0:       9d                      popfq  
ffffffff81155fb1:       e8 2a 5c fd ff          callq  ffffffff8112bbe0 <trace_hardirqs_off>
ffffffff81155fb6:       65 8b 05 5b 66 eb 7e    mov    %gs:0x7eeb665b(%rip),%eax        # c618 <__preempt_count>
ffffffff81155fbd:       a9 00 00 0f 00          test   $0xf0000,%eax
ffffffff81155fc2:       74 25                   je     ffffffff81155fe9 <del_timer_sync+0x99>
ffffffff81155fc4:       f6 43 2a 20             testb  $0x20,0x2a(%rbx)
ffffffff81155fc8:       75 1f                   jne    ffffffff81155fe9 <del_timer_sync+0x99>
ffffffff81155fca:       be 61 04 00 00          mov    $0x461,%esi
ffffffff81155fcf:       48 c7 c7 09 87 f3 81    mov    $0xffffffff81f38709,%rdi
ffffffff81155fd6:       e8 15 03 f8 ff          callq  ffffffff810d62f0 <warn_slowpath_null>
ffffffff81155fdb:       48 89 df                mov    %rbx,%rdi
ffffffff81155fde:       e8 fd fe ff ff          callq  ffffffff81155ee0 <try_to_del_timer_sync>
ffffffff81155fe3:       85 c0                   test   %eax,%eax
ffffffff81155fe5:       79 0e                   jns    ffffffff81155ff5 <del_timer_sync+0xa5>
ffffffff81155fe7:       f3 90                   pause  
ffffffff81155fe9:       48 89 df                mov    %rbx,%rdi
ffffffff81155fec:       e8 ef fe ff ff          callq  ffffffff81155ee0 <try_to_del_timer_sync>
ffffffff81155ff1:       85 c0                   test   %eax,%eax
ffffffff81155ff3:       78 f2                   js     ffffffff81155fe7 <del_timer_sync+0x97>
ffffffff81155ff5:       48 83 c4 08             add    $0x8,%rsp
ffffffff81155ff9:       5b                      pop    %rbx
ffffffff81155ffa:       41 5c                   pop    %r12
ffffffff81155ffc:       41 5d                   pop    %r13
ffffffff81155ffe:       5d                      pop    %rbp
ffffffff81155fff:       c3                      retq   
ffffffff81156000:       e8 4b 8b fd ff          callq  ffffffff8112eb50 <trace_hardirqs_on>
ffffffff81156005:       41 54                   push   %r12
ffffffff81156007:       9d                      popfq  
ffffffff81156008:       eb ac                   jmp    ffffffff81155fb6 <del_timer_sync+0x66>
ffffffff8115600a:       66 0f 1f 44 00 00       nopw   0x0(%rax,%rax,1)

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#1348313

FromSteven Rostedt <rostedt@goodmis.org>
Date2016-03-02 17:40 +0100
Message-ID<r8hYD-1Lj-45@gated-at.bofh.it>
In reply to#1348298
On Wed, 2 Mar 2016 17:24:12 +0100
Peter Zijlstra <peterz@infradead.org> wrote:

> On Wed, Mar 02, 2016 at 04:53:36PM +0100, Sedat Dilek wrote:
> > ffffffff8110f570 <del_timer_sync>:
> > ffffffff8110f570:	55                   	push   %rbp
> > ffffffff8110f571:	48 89 e5             	mov    %rsp,%rbp
> > ffffffff8110f574:	41 57                	push   %r15
> > ffffffff8110f576:	41 56                	push   %r14
> > ffffffff8110f578:	53                   	push   %rbx
> > ffffffff8110f579:	48 83 ec 28          	sub    $0x28,%rsp  
> 
> stack offset is 0x28 bytes [*]

Actually, isn't it really 0x40 bytes? The stack pushed 3 words (8 bytes
each) before doing the subtract. 0x28 == 40 bytes, 3 * 8 = 24,
40 + 24 = 64 == 0x40.

> 
> > ffffffff8110f57d:	48 89 fb             	mov    %rdi,%rbx
> > ffffffff8110f580:	e8 6b 6e 80 00       	callq  ffffffff819163f0 <mcount>
> > ffffffff8110f585:	e8 66 6e 80 00       	callq  ffffffff819163f0 <mcount>
> > ffffffff8110f58a:	e8 61 6e 80 00       	callq  ffffffff819163f0 <mcount>
> > ffffffff8110f58f:	e8 5c 6e 80 00       	callq  ffffffff819163f0 <mcount>  
> 
> Your compiler is on drugs!

Totally agree!


[..]

> 
> > ffffffff8110f5fd:	4c 89 75 d0          	mov    %r14,-0x30(%rbp)
> > ffffffff8110f601:	ff 75 d0             	pushq  -0x30(%rbp)
> > ffffffff8110f604:	9d                   	popfq    
> 
> put r14 into -0x30(rbp) and pushes/pops that, see [*] this is 8 bytes
> over stack ?!

But from rbp, the stack is 0x40 bytes. This may be fine.

-- Steve

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#1348315

FromPeter Zijlstra <peterz@infradead.org>
Date2016-03-02 17:50 +0100
Message-ID<r8i8i-1OI-3@gated-at.bofh.it>
In reply to#1348313
On Wed, Mar 02, 2016 at 11:35:35AM -0500, Steven Rostedt wrote:
> On Wed, 2 Mar 2016 17:24:12 +0100
> Peter Zijlstra <peterz@infradead.org> wrote:
> 
> > On Wed, Mar 02, 2016 at 04:53:36PM +0100, Sedat Dilek wrote:
> > > ffffffff8110f570 <del_timer_sync>:
> > > ffffffff8110f570:	55                   	push   %rbp
> > > ffffffff8110f571:	48 89 e5             	mov    %rsp,%rbp
> > > ffffffff8110f574:	41 57                	push   %r15
> > > ffffffff8110f576:	41 56                	push   %r14
> > > ffffffff8110f578:	53                   	push   %rbx
> > > ffffffff8110f579:	48 83 ec 28          	sub    $0x28,%rsp  
> > 
> > stack offset is 0x28 bytes [*]
> 
> Actually, isn't it really 0x40 bytes? The stack pushed 3 words (8 bytes
> each) before doing the subtract. 0x28 == 40 bytes, 3 * 8 = 24,
> 40 + 24 = 64 == 0x40.

> > > ffffffff8110f5fd:	4c 89 75 d0          	mov    %r14,-0x30(%rbp)
> > > ffffffff8110f601:	ff 75 d0             	pushq  -0x30(%rbp)
> > > ffffffff8110f604:	9d                   	popfq    
> > 
> > put r14 into -0x30(rbp) and pushes/pops that, see [*] this is 8 bytes
> > over stack ?!
> 
> But from rbp, the stack is 0x40 bytes. This may be fine.

Ah indeed.

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#1348316

FromSedat Dilek <sedat.dilek@gmail.com>
Date2016-03-02 17:50 +0100
Message-ID<r8i8i-1OI-7@gated-at.bofh.it>
In reply to#1348298
On 3/2/16, Peter Zijlstra <peterz@infradead.org> wrote:
> On Wed, Mar 02, 2016 at 04:53:36PM +0100, Sedat Dilek wrote:
>> ffffffff8110f570 <del_timer_sync>:
>> ffffffff8110f570:	55                   	push   %rbp
>> ffffffff8110f571:	48 89 e5             	mov    %rsp,%rbp
>> ffffffff8110f574:	41 57                	push   %r15
>> ffffffff8110f576:	41 56                	push   %r14
>> ffffffff8110f578:	53                   	push   %rbx
>> ffffffff8110f579:	48 83 ec 28          	sub    $0x28,%rsp
>
> stack offset is 0x28 bytes [*]
>
>> ffffffff8110f57d:	48 89 fb             	mov    %rdi,%rbx
>> ffffffff8110f580:	e8 6b 6e 80 00       	callq  ffffffff819163f0 <mcount>
>> ffffffff8110f585:	e8 66 6e 80 00       	callq  ffffffff819163f0 <mcount>
>> ffffffff8110f58a:	e8 61 6e 80 00       	callq  ffffffff819163f0 <mcount>
>> ffffffff8110f58f:	e8 5c 6e 80 00       	callq  ffffffff819163f0 <mcount>
>
> Your compiler is on drugs!
>
>> ffffffff8110f594:	9c                   	pushfq
>> ffffffff8110f595:	8f 45 e0             	popq   -0x20(%rbp)
>
> Saves flags in -0x20(%rbp)
>
>> ffffffff8110f598:	4c 8b 7d e0          	mov    -0x20(%rbp),%r15
>
> And in %r15
>
> /me wonders what's wrong with: popf %r15
>
>> ffffffff8110f59c:	e8 4f 6e 80 00       	callq  ffffffff819163f0 <mcount>
>> ffffffff8110f5a1:	e8 4a 6e 80 00       	callq  ffffffff819163f0 <mcount>
>> ffffffff8110f5a6:	fa                   	cli
>> ffffffff8110f5a7:	e8 84 cb fc ff       	callq  ffffffff810dc130
>> <trace_hardirqs_off>
>> ffffffff8110f5ac:	4c 8d 73 50          	lea    0x50(%rbx),%r14
>> ffffffff8110f5b0:	48 c7 04 24 b0 f5 10 	movq   $0xffffffff8110f5b0,(%rsp)
>> ffffffff8110f5b7:	81
>> ffffffff8110f5b8:	31 f6                	xor    %esi,%esi
>> ffffffff8110f5ba:	31 d2                	xor    %edx,%edx
>> ffffffff8110f5bc:	31 c9                	xor    %ecx,%ecx
>> ffffffff8110f5be:	41 b8 01 00 00 00    	mov    $0x1,%r8d
>> ffffffff8110f5c4:	45 31 c9             	xor    %r9d,%r9d
>> ffffffff8110f5c7:	4c 89 f7             	mov    %r14,%rdi
>> ffffffff8110f5ca:	e8 c1 e5 fc ff       	callq  ffffffff810ddb90
>> <lock_acquire>
>> ffffffff8110f5cf:	be 01 00 00 00       	mov    $0x1,%esi
>> ffffffff8110f5d4:	48 c7 c2 cf f5 10 81 	mov    $0xffffffff8110f5cf,%rdx
>> ffffffff8110f5db:	4c 89 f7             	mov    %r14,%rdi
>> ffffffff8110f5de:	e8 8d 08 fd ff       	callq  ffffffff810dfe70
>> <lock_release>
>> ffffffff8110f5e3:	e8 08 6e 80 00       	callq  ffffffff819163f0 <mcount>
>
>> ffffffff8110f5e8:	4c 89 f8             	mov    %r15,%rax
>> ffffffff8110f5eb:	49 89 c6             	mov    %rax,%r14
>
> Moves r15 into r14 through rax
>
>
>> ffffffff8110f5ee:	f6 c4 02             	test   $0x2,%ah
>> ffffffff8110f5f1:	75 19                	jne    ffffffff8110f60c
>> <del_timer_sync+0x9c>
>> ffffffff8110f5f3:	e8 f8 6d 80 00       	callq  ffffffff819163f0 <mcount>
>> ffffffff8110f5f8:	e8 f3 6d 80 00       	callq  ffffffff819163f0 <mcount>
>
>
>> ffffffff8110f5fd:	4c 89 75 d0          	mov    %r14,-0x30(%rbp)
>> ffffffff8110f601:	ff 75 d0             	pushq  -0x30(%rbp)
>> ffffffff8110f604:	9d                   	popfq
>
> put r14 into -0x30(rbp) and pushes/pops that, see [*] this is 8 bytes
> over stack ?!
>
>> ffffffff8110f605:	e8 26 cb fc ff       	callq  ffffffff810dc130
>> <trace_hardirqs_off>
>> ffffffff8110f60a:	eb 17                	jmp    ffffffff8110f623
>> <del_timer_sync+0xb3>
>> ffffffff8110f60c:	e8 2f cb fc ff       	callq  ffffffff810dc140
>> <trace_hardirqs_on>
>> ffffffff8110f611:	e8 da 6d 80 00       	callq  ffffffff819163f0 <mcount>
>> ffffffff8110f616:	e8 d5 6d 80 00       	callq  ffffffff819163f0 <mcount>
>> ffffffff8110f61b:	4c 89 75 d8          	mov    %r14,-0x28(%rbp)
>> ffffffff8110f61f:	ff 75 d8             	pushq  -0x28(%rbp)
>> ffffffff8110f622:	9d                   	popfq
>
> puts r14 into -0x28(rbp) and pushes/pops that
>
>> ffffffff8110f623:	e8 c8 6d 80 00       	callq  ffffffff819163f0 <mcount>
>> ffffffff8110f628:	65 8b 04 25 d4 ae 00 	mov    %gs:0xaed4,%eax
>> ffffffff8110f62f:	00
>> ffffffff8110f630:	a9 00 00 0f 00       	test   $0xf0000,%eax
>> ffffffff8110f635:	74 25                	je     ffffffff8110f65c
>> <del_timer_sync+0xec>
>> ffffffff8110f637:	f6 43 2a 20          	testb  $0x20,0x2a(%rbx)
>> ffffffff8110f63b:	75 1f                	jne    ffffffff8110f65c
>> <del_timer_sync+0xec>
>> ffffffff8110f63d:	48 c7 c7 04 54 c5 81 	mov    $0xffffffff81c55404,%rdi
>> ffffffff8110f644:	be 61 04 00 00       	mov    $0x461,%esi
>> ffffffff8110f649:	e8 12 c4 f6 ff       	callq  ffffffff8107ba60
>> <warn_slowpath_null>
>> ffffffff8110f64e:	eb 0c                	jmp    ffffffff8110f65c
>> <del_timer_sync+0xec>
>> ffffffff8110f650:	e8 9b 6d 80 00       	callq  ffffffff819163f0 <mcount>
>> ffffffff8110f655:	e8 96 6d 80 00       	callq  ffffffff819163f0 <mcount>
>> ffffffff8110f65a:	f3 90                	pause
>> ffffffff8110f65c:	48 89 df             	mov    %rbx,%rdi
>> ffffffff8110f65f:	e8 4c fe ff ff       	callq  ffffffff8110f4b0
>> <try_to_del_timer_sync>
>> ffffffff8110f664:	85 c0                	test   %eax,%eax
>> ffffffff8110f666:	78 e8                	js     ffffffff8110f650
>> <del_timer_sync+0xe0>
>> ffffffff8110f668:	48 83 c4 28          	add    $0x28,%rsp
>> ffffffff8110f66c:	5b                   	pop    %rbx
>> ffffffff8110f66d:	41 5e                	pop    %r14
>> ffffffff8110f66f:	41 5f                	pop    %r15
>> ffffffff8110f671:	5d                   	pop    %rbp
>> ffffffff8110f672:	c3                   	retq
>> ffffffff8110f673:	66 66 66 66 2e 0f 1f 	data32 data32 data32 nopw
>> %cs:0x0(%rax,%rax,1)
>> ffffffff8110f67a:	84 00 00 00 00 00
>
>
> That LLVM generate disgusting code, as a contrast, this is what my GCC
> makes of this:
>
> ffffffff81155f50 <del_timer_sync>:
> ffffffff81155f50:       e8 bb 02 9c 00          callq  ffffffff81b16210
> <__fentry__>
> ffffffff81155f55:       55                      push   %rbp
> ffffffff81155f56:       48 89 e5                mov    %rsp,%rbp
> ffffffff81155f59:       41 55                   push   %r13
> ffffffff81155f5b:       41 54                   push   %r12
> ffffffff81155f5d:       53                      push   %rbx
> ffffffff81155f5e:       48 89 fb                mov    %rdi,%rbx
> ffffffff81155f61:       48 83 ec 08             sub    $0x8,%rsp
> ffffffff81155f65:       9c                      pushfq
> ffffffff81155f66:       41 5c                   pop    %r12
> ffffffff81155f68:       fa                      cli
> ffffffff81155f69:       e8 72 5c fd ff          callq  ffffffff8112bbe0
> <trace_hardirqs_off>
> ffffffff81155f6e:       4c 8d 6b 50             lea    0x50(%rbx),%r13
> ffffffff81155f72:       45 31 c9                xor    %r9d,%r9d
> ffffffff81155f75:       31 c9                   xor    %ecx,%ecx
> ffffffff81155f77:       31 d2                   xor    %edx,%edx
> ffffffff81155f79:       31 f6                   xor    %esi,%esi
> ffffffff81155f7b:       4c 89 ef                mov    %r13,%rdi
> ffffffff81155f7e:       48 c7 04 24 55 5f 15    movq
> $0xffffffff81155f55,(%rsp)
> ffffffff81155f85:       81
> ffffffff81155f86:       41 b8 01 00 00 00       mov    $0x1,%r8d
> ffffffff81155f8c:       e8 3f b3 fd ff          callq  ffffffff811312d0
> <lock_acquire>
> ffffffff81155f91:       48 c7 c2 55 5f 15 81    mov
> $0xffffffff81155f55,%rdx
> ffffffff81155f98:       be 01 00 00 00          mov    $0x1,%esi
> ffffffff81155f9d:       4c 89 ef                mov    %r13,%rdi
> ffffffff81155fa0:       e8 0b b5 fd ff          callq  ffffffff811314b0
> <lock_release>
> ffffffff81155fa5:       41 f7 c4 00 02 00 00    test   $0x200,%r12d
> ffffffff81155fac:       75 52                   jne    ffffffff81156000
> <del_timer_sync+0xb0>
> ffffffff81155fae:       41 54                   push   %r12
> ffffffff81155fb0:       9d                      popfq
> ffffffff81155fb1:       e8 2a 5c fd ff          callq  ffffffff8112bbe0
> <trace_hardirqs_off>
> ffffffff81155fb6:       65 8b 05 5b 66 eb 7e    mov
> %gs:0x7eeb665b(%rip),%eax        # c618 <__preempt_count>
> ffffffff81155fbd:       a9 00 00 0f 00          test   $0xf0000,%eax
> ffffffff81155fc2:       74 25                   je     ffffffff81155fe9
> <del_timer_sync+0x99>
> ffffffff81155fc4:       f6 43 2a 20             testb  $0x20,0x2a(%rbx)
> ffffffff81155fc8:       75 1f                   jne    ffffffff81155fe9
> <del_timer_sync+0x99>
> ffffffff81155fca:       be 61 04 00 00          mov    $0x461,%esi
> ffffffff81155fcf:       48 c7 c7 09 87 f3 81    mov
> $0xffffffff81f38709,%rdi
> ffffffff81155fd6:       e8 15 03 f8 ff          callq  ffffffff810d62f0
> <warn_slowpath_null>
> ffffffff81155fdb:       48 89 df                mov    %rbx,%rdi
> ffffffff81155fde:       e8 fd fe ff ff          callq  ffffffff81155ee0
> <try_to_del_timer_sync>
> ffffffff81155fe3:       85 c0                   test   %eax,%eax
> ffffffff81155fe5:       79 0e                   jns    ffffffff81155ff5
> <del_timer_sync+0xa5>
> ffffffff81155fe7:       f3 90                   pause
> ffffffff81155fe9:       48 89 df                mov    %rbx,%rdi
> ffffffff81155fec:       e8 ef fe ff ff          callq  ffffffff81155ee0
> <try_to_del_timer_sync>
> ffffffff81155ff1:       85 c0                   test   %eax,%eax
> ffffffff81155ff3:       78 f2                   js     ffffffff81155fe7
> <del_timer_sync+0x97>
> ffffffff81155ff5:       48 83 c4 08             add    $0x8,%rsp
> ffffffff81155ff9:       5b                      pop    %rbx
> ffffffff81155ffa:       41 5c                   pop    %r12
> ffffffff81155ffc:       41 5d                   pop    %r13
> ffffffff81155ffe:       5d                      pop    %rbp
> ffffffff81155fff:       c3                      retq
> ffffffff81156000:       e8 4b 8b fd ff          callq  ffffffff8112eb50
> <trace_hardirqs_on>
> ffffffff81156005:       41 54                   push   %r12
> ffffffff81156007:       9d                      popfq
> ffffffff81156008:       eb ac                   jmp    ffffffff81155fb6
> <del_timer_sync+0x66>
> ffffffff8115600a:       66 0f 1f 44 00 00       nopw   0x0(%rax,%rax,1)
>

OK, I cannot say much to your analysis.

The full make-lines look differently.

GCC for example has '-mfentry -DCC_USING_FENTRY'.

[ CLANG ]

mycompiler -Wp,-MD,kernel/.workqueue.o.d  -nostdinc -isystem
/opt/llvm-toolchain-3.8.0rc3/bin/../lib/clang/3.8.0/include -nostdinc
-isystem /opt/llvm-toolchain-3.8.0rc3/bin/../lib/clang/3.8.0/include
-I./arch/x86/include -Iarch/x86/include/generated/uapi
-Iarch/x86/include/generated  -Iinclude -I./arch/x86/include/uapi
-Iarch/x86/include/generated/uapi -I./include/uapi
-Iinclude/generated/uapi -include ./include/linux/kconfig.h
-D__KERNEL__ -Qunused-arguments -Wno-unknown-warning-option -Wall
-Wundef -Wstrict-prototypes -Wno-trigraphs -fno-strict-aliasing
-fno-common -Werror-implicit-function-declaration -Wno-format-security
-std=gnu89 -no-integrated-as -mno-sse -mno-mmx -mno-sse2 -mno-3dnow
-mno-avx -m64 -mtune=generic -mno-red-zone -mcmodel=kernel
-funit-at-a-time -DCONFIG_X86_X32_ABI -DCONFIG_AS_CFI=1
-DCONFIG_AS_CFI_SIGNAL_FRAME=1 -DCONFIG_AS_CFI_SECTIONS=1
-DCONFIG_AS_FXSAVEQ=1 -DCONFIG_AS_SSSE3=1 -DCONFIG_AS_CRC32=1
-DCONFIG_AS_AVX=1 -DCONFIG_AS_AVX2=1 -pipe -Wno-sign-compare
-fno-asynchronous-unwind-tables -O2 -Wframe-larger-than=1024
-fno-stack-protector -Wno-unused-variable
-Wno-format-invalid-specifier -Wno-gnu -Wno-asm-operand-widths
-Wno-initializer-overrides -fno-builtin -Wno-tautological-compare
-mno-global-merge -fno-omit-frame-pointer -fno-optimize-sibling-calls
-pg -Wdeclaration-after-statement -Wno-pointer-sign
-fno-strict-overflow -Werror=implicit-int -Werror=strict-prototypes
-Werror=date-time -Wno-initializer-overrides -Wno-unused-value
-Wno-format -Wno-unknown-warning-option -Wno-sign-compare
-Wno-format-zero-length -Wno-uninitialized    -D"KBUILD_STR(s)=#s"
-D"KBUILD_BASENAME=KBUILD_STR(workqueue)"
-D"KBUILD_MODNAME=KBUILD_STR(workqueue)" -c -o kernel/.tmp_workqueue.o
kernel/workqueue.c

mycompiler -Wp,-MD,kernel/time/.timer.o.d  -nostdinc -isystem
/opt/llvm-toolchain-3.8.0rc3/bin/../lib/clang/3.8.0/include -nostdinc
-isystem /opt/llvm-toolchain-3.8.0rc3/bin/../lib/clang/3.8.0/include
-I./arch/x86/include -Iarch/x86/include/generated/uapi
-Iarch/x86/include/generated  -Iinclude -I./arch/x86/include/uapi
-Iarch/x86/include/generated/uapi -I./include/uapi
-Iinclude/generated/uapi -include ./include/linux/kconfig.h
-D__KERNEL__ -Qunused-arguments -Wno-unknown-warning-option -Wall
-Wundef -Wstrict-prototypes -Wno-trigraphs -fno-strict-aliasing
-fno-common -Werror-implicit-function-declaration -Wno-format-security
-std=gnu89 -no-integrated-as -mno-sse -mno-mmx -mno-sse2 -mno-3dnow
-mno-avx -m64 -mtune=generic -mno-red-zone -mcmodel=kernel
-funit-at-a-time -DCONFIG_X86_X32_ABI -DCONFIG_AS_CFI=1
-DCONFIG_AS_CFI_SIGNAL_FRAME=1 -DCONFIG_AS_CFI_SECTIONS=1
-DCONFIG_AS_FXSAVEQ=1 -DCONFIG_AS_SSSE3=1 -DCONFIG_AS_CRC32=1
-DCONFIG_AS_AVX=1 -DCONFIG_AS_AVX2=1 -pipe -Wno-sign-compare
-fno-asynchronous-unwind-tables -O2 -Wframe-larger-than=1024
-fno-stack-protector -Wno-unused-variable
-Wno-format-invalid-specifier -Wno-gnu -Wno-asm-operand-widths
-Wno-initializer-overrides -fno-builtin -Wno-tautological-compare
-mno-global-merge -fno-omit-frame-pointer -fno-optimize-sibling-calls
-pg -Wdeclaration-after-statement -Wno-pointer-sign
-fno-strict-overflow -Werror=implicit-int -Werror=strict-prototypes
-Werror=date-time -Wno-initializer-overrides -Wno-unused-value
-Wno-format -Wno-unknown-warning-option -Wno-sign-compare
-Wno-format-zero-length -Wno-uninitialized    -D"KBUILD_STR(s)=#s"
-D"KBUILD_BASENAME=KBUILD_STR(timer)"
-D"KBUILD_MODNAME=KBUILD_STR(timer)" -c -o kernel/time/.tmp_timer.o
kernel/time/timer.c

[ GCC ]

mycompiler -Wp,-MD,kernel/.workqueue.o.d  -nostdinc -isystem
/usr/lib/gcc/x86_64-linux-gnu/4.9/include -nostdinc -isystem
/usr/lib/gcc/x86_64-linux-gnu/4.9/include -I./arch/x86/include
-Iarch/x86/include/generated/uapi -Iarch/x86/include/generated
-Iinclude -I./arch/x86/include/uapi -Iarch/x86/include/generated/uapi
-I./include/uapi -Iinclude/generated/uapi -include
./include/linux/kconfig.h -D__KERNEL__ -Wall -Wundef
-Wstrict-prototypes -Wno-trigraphs -fno-strict-aliasing -fno-common
-Werror-implicit-function-declaration -Wno-format-security -std=gnu89
-mno-sse -mno-mmx -mno-sse2 -mno-3dnow -mno-avx -m64 -falign-jumps=1
-falign-loops=1 -mno-80387 -mno-fp-ret-in-387
-mpreferred-stack-boundary=3 -mtune=generic -mno-red-zone
-mcmodel=kernel -funit-at-a-time -maccumulate-outgoing-args
-DCONFIG_X86_X32_ABI -DCONFIG_AS_CFI=1 -DCONFIG_AS_CFI_SIGNAL_FRAME=1
-DCONFIG_AS_CFI_SECTIONS=1 -DCONFIG_AS_FXSAVEQ=1 -DCONFIG_AS_SSSE3=1
-DCONFIG_AS_CRC32=1 -DCONFIG_AS_AVX=1 -DCONFIG_AS_AVX2=1 -pipe
-Wno-sign-compare -fno-asynchronous-unwind-tables
-fno-delete-null-pointer-checks -O2 --param=allow-store-data-races=0
-Wframe-larger-than=1024 -fno-stack-protector
-Wno-unused-but-set-variable -fno-omit-frame-pointer
-fno-optimize-sibling-calls -fno-var-tracking-assignments -pg -mfentry
-DCC_USING_FENTRY -Wdeclaration-after-statement -Wno-pointer-sign
-fno-strict-overflow -fconserve-stack -Werror=implicit-int
-Werror=strict-prototypes -Werror=date-time -DCC_HAVE_ASM_GOTO
-D"KBUILD_STR(s)=#s" -D"KBUILD_BASENAME=KBUILD_STR(workqueue)"
-D"KBUILD_MODNAME=KBUILD_STR(workqueue)" -c -o kernel/.tmp_workqueue.o
kernel/workqueue.c

mycompiler -Wp,-MD,kernel/time/.timer.o.d  -nostdinc -isystem
/usr/lib/gcc/x86_64-linux-gnu/4.9/include -nostdinc -isystem
/usr/lib/gcc/x86_64-linux-gnu/4.9/include -I./arch/x86/include
-Iarch/x86/include/generated/uapi -Iarch/x86/include/generated
-Iinclude -I./arch/x86/include/uapi -Iarch/x86/include/generated/uapi
-I./include/uapi -Iinclude/generated/uapi -include
./include/linux/kconfig.h -D__KERNEL__ -Wall -Wundef
-Wstrict-prototypes -Wno-trigraphs -fno-strict-aliasing -fno-common
-Werror-implicit-function-declaration -Wno-format-security -std=gnu89
-mno-sse -mno-mmx -mno-sse2 -mno-3dnow -mno-avx -m64 -falign-jumps=1
-falign-loops=1 -mno-80387 -mno-fp-ret-in-387
-mpreferred-stack-boundary=3 -mtune=generic -mno-red-zone
-mcmodel=kernel -funit-at-a-time -maccumulate-outgoing-args
-DCONFIG_X86_X32_ABI -DCONFIG_AS_CFI=1 -DCONFIG_AS_CFI_SIGNAL_FRAME=1
-DCONFIG_AS_CFI_SECTIONS=1 -DCONFIG_AS_FXSAVEQ=1 -DCONFIG_AS_SSSE3=1
-DCONFIG_AS_CRC32=1 -DCONFIG_AS_AVX=1 -DCONFIG_AS_AVX2=1 -pipe
-Wno-sign-compare -fno-asynchronous-unwind-tables
-fno-delete-null-pointer-checks -O2 --param=allow-store-data-races=0
-Wframe-larger-than=1024 -fno-stack-protector
-Wno-unused-but-set-variable -fno-omit-frame-pointer
-fno-optimize-sibling-calls -fno-var-tracking-assignments -pg -mfentry
-DCC_USING_FENTRY -Wdeclaration-after-statement -Wno-pointer-sign
-fno-strict-overflow -fconserve-stack -Werror=implicit-int
-Werror=strict-prototypes -Werror=date-time -DCC_HAVE_ASM_GOTO
-D"KBUILD_STR(s)=#s" -D"KBUILD_BASENAME=KBUILD_STR(timer)"
-D"KBUILD_MODNAME=KBUILD_STR(timer)" -c -o kernel/time/.tmp_timer.o
kernel/time/timer.c

I can try to use the make-line of GCC and re-compile.

- Sedat -

[toc] | [prev] | [next] | [standalone]

#1348328

FromSedat Dilek <sedat.dilek@gmail.com>
Date2016-03-02 18:00 +0100
Message-ID<r8ihY-1S0-9@gated-at.bofh.it>
In reply to#1348316
On 3/2/16, Sedat Dilek <sedat.dilek@gmail.com> wrote:
> On 3/2/16, Peter Zijlstra <peterz@infradead.org> wrote:
>> On Wed, Mar 02, 2016 at 04:53:36PM +0100, Sedat Dilek wrote:
>>> ffffffff8110f570 <del_timer_sync>:
>>> ffffffff8110f570:	55                   	push   %rbp
>>> ffffffff8110f571:	48 89 e5             	mov    %rsp,%rbp
>>> ffffffff8110f574:	41 57                	push   %r15
>>> ffffffff8110f576:	41 56                	push   %r14
>>> ffffffff8110f578:	53                   	push   %rbx
>>> ffffffff8110f579:	48 83 ec 28          	sub    $0x28,%rsp
>>
>> stack offset is 0x28 bytes [*]
>>
>>> ffffffff8110f57d:	48 89 fb             	mov    %rdi,%rbx
>>> ffffffff8110f580:	e8 6b 6e 80 00       	callq  ffffffff819163f0 <mcount>
>>> ffffffff8110f585:	e8 66 6e 80 00       	callq  ffffffff819163f0 <mcount>
>>> ffffffff8110f58a:	e8 61 6e 80 00       	callq  ffffffff819163f0 <mcount>
>>> ffffffff8110f58f:	e8 5c 6e 80 00       	callq  ffffffff819163f0 <mcount>
>>
>> Your compiler is on drugs!
>>
>>> ffffffff8110f594:	9c                   	pushfq
>>> ffffffff8110f595:	8f 45 e0             	popq   -0x20(%rbp)
>>
>> Saves flags in -0x20(%rbp)
>>
>>> ffffffff8110f598:	4c 8b 7d e0          	mov    -0x20(%rbp),%r15
>>
>> And in %r15
>>
>> /me wonders what's wrong with: popf %r15
>>
>>> ffffffff8110f59c:	e8 4f 6e 80 00       	callq  ffffffff819163f0 <mcount>
>>> ffffffff8110f5a1:	e8 4a 6e 80 00       	callq  ffffffff819163f0 <mcount>
>>> ffffffff8110f5a6:	fa                   	cli
>>> ffffffff8110f5a7:	e8 84 cb fc ff       	callq  ffffffff810dc130
>>> <trace_hardirqs_off>
>>> ffffffff8110f5ac:	4c 8d 73 50          	lea    0x50(%rbx),%r14
>>> ffffffff8110f5b0:	48 c7 04 24 b0 f5 10 	movq
>>> $0xffffffff8110f5b0,(%rsp)
>>> ffffffff8110f5b7:	81
>>> ffffffff8110f5b8:	31 f6                	xor    %esi,%esi
>>> ffffffff8110f5ba:	31 d2                	xor    %edx,%edx
>>> ffffffff8110f5bc:	31 c9                	xor    %ecx,%ecx
>>> ffffffff8110f5be:	41 b8 01 00 00 00    	mov    $0x1,%r8d
>>> ffffffff8110f5c4:	45 31 c9             	xor    %r9d,%r9d
>>> ffffffff8110f5c7:	4c 89 f7             	mov    %r14,%rdi
>>> ffffffff8110f5ca:	e8 c1 e5 fc ff       	callq  ffffffff810ddb90
>>> <lock_acquire>
>>> ffffffff8110f5cf:	be 01 00 00 00       	mov    $0x1,%esi
>>> ffffffff8110f5d4:	48 c7 c2 cf f5 10 81 	mov    $0xffffffff8110f5cf,%rdx
>>> ffffffff8110f5db:	4c 89 f7             	mov    %r14,%rdi
>>> ffffffff8110f5de:	e8 8d 08 fd ff       	callq  ffffffff810dfe70
>>> <lock_release>
>>> ffffffff8110f5e3:	e8 08 6e 80 00       	callq  ffffffff819163f0 <mcount>
>>
>>> ffffffff8110f5e8:	4c 89 f8             	mov    %r15,%rax
>>> ffffffff8110f5eb:	49 89 c6             	mov    %rax,%r14
>>
>> Moves r15 into r14 through rax
>>
>>
>>> ffffffff8110f5ee:	f6 c4 02             	test   $0x2,%ah
>>> ffffffff8110f5f1:	75 19                	jne    ffffffff8110f60c
>>> <del_timer_sync+0x9c>
>>> ffffffff8110f5f3:	e8 f8 6d 80 00       	callq  ffffffff819163f0 <mcount>
>>> ffffffff8110f5f8:	e8 f3 6d 80 00       	callq  ffffffff819163f0 <mcount>
>>
>>
>>> ffffffff8110f5fd:	4c 89 75 d0          	mov    %r14,-0x30(%rbp)
>>> ffffffff8110f601:	ff 75 d0             	pushq  -0x30(%rbp)
>>> ffffffff8110f604:	9d                   	popfq
>>
>> put r14 into -0x30(rbp) and pushes/pops that, see [*] this is 8 bytes
>> over stack ?!
>>
>>> ffffffff8110f605:	e8 26 cb fc ff       	callq  ffffffff810dc130
>>> <trace_hardirqs_off>
>>> ffffffff8110f60a:	eb 17                	jmp    ffffffff8110f623
>>> <del_timer_sync+0xb3>
>>> ffffffff8110f60c:	e8 2f cb fc ff       	callq  ffffffff810dc140
>>> <trace_hardirqs_on>
>>> ffffffff8110f611:	e8 da 6d 80 00       	callq  ffffffff819163f0 <mcount>
>>> ffffffff8110f616:	e8 d5 6d 80 00       	callq  ffffffff819163f0 <mcount>
>>> ffffffff8110f61b:	4c 89 75 d8          	mov    %r14,-0x28(%rbp)
>>> ffffffff8110f61f:	ff 75 d8             	pushq  -0x28(%rbp)
>>> ffffffff8110f622:	9d                   	popfq
>>
>> puts r14 into -0x28(rbp) and pushes/pops that
>>
>>> ffffffff8110f623:	e8 c8 6d 80 00       	callq  ffffffff819163f0 <mcount>
>>> ffffffff8110f628:	65 8b 04 25 d4 ae 00 	mov    %gs:0xaed4,%eax
>>> ffffffff8110f62f:	00
>>> ffffffff8110f630:	a9 00 00 0f 00       	test   $0xf0000,%eax
>>> ffffffff8110f635:	74 25                	je     ffffffff8110f65c
>>> <del_timer_sync+0xec>
>>> ffffffff8110f637:	f6 43 2a 20          	testb  $0x20,0x2a(%rbx)
>>> ffffffff8110f63b:	75 1f                	jne    ffffffff8110f65c
>>> <del_timer_sync+0xec>
>>> ffffffff8110f63d:	48 c7 c7 04 54 c5 81 	mov    $0xffffffff81c55404,%rdi
>>> ffffffff8110f644:	be 61 04 00 00       	mov    $0x461,%esi
>>> ffffffff8110f649:	e8 12 c4 f6 ff       	callq  ffffffff8107ba60
>>> <warn_slowpath_null>
>>> ffffffff8110f64e:	eb 0c                	jmp    ffffffff8110f65c
>>> <del_timer_sync+0xec>
>>> ffffffff8110f650:	e8 9b 6d 80 00       	callq  ffffffff819163f0 <mcount>
>>> ffffffff8110f655:	e8 96 6d 80 00       	callq  ffffffff819163f0 <mcount>
>>> ffffffff8110f65a:	f3 90                	pause
>>> ffffffff8110f65c:	48 89 df             	mov    %rbx,%rdi
>>> ffffffff8110f65f:	e8 4c fe ff ff       	callq  ffffffff8110f4b0
>>> <try_to_del_timer_sync>
>>> ffffffff8110f664:	85 c0                	test   %eax,%eax
>>> ffffffff8110f666:	78 e8                	js     ffffffff8110f650
>>> <del_timer_sync+0xe0>
>>> ffffffff8110f668:	48 83 c4 28          	add    $0x28,%rsp
>>> ffffffff8110f66c:	5b                   	pop    %rbx
>>> ffffffff8110f66d:	41 5e                	pop    %r14
>>> ffffffff8110f66f:	41 5f                	pop    %r15
>>> ffffffff8110f671:	5d                   	pop    %rbp
>>> ffffffff8110f672:	c3                   	retq
>>> ffffffff8110f673:	66 66 66 66 2e 0f 1f 	data32 data32 data32 nopw
>>> %cs:0x0(%rax,%rax,1)
>>> ffffffff8110f67a:	84 00 00 00 00 00
>>
>>
>> That LLVM generate disgusting code, as a contrast, this is what my GCC
>> makes of this:
>>
>> ffffffff81155f50 <del_timer_sync>:
>> ffffffff81155f50:       e8 bb 02 9c 00          callq  ffffffff81b16210
>> <__fentry__>
>> ffffffff81155f55:       55                      push   %rbp
>> ffffffff81155f56:       48 89 e5                mov    %rsp,%rbp
>> ffffffff81155f59:       41 55                   push   %r13
>> ffffffff81155f5b:       41 54                   push   %r12
>> ffffffff81155f5d:       53                      push   %rbx
>> ffffffff81155f5e:       48 89 fb                mov    %rdi,%rbx
>> ffffffff81155f61:       48 83 ec 08             sub    $0x8,%rsp
>> ffffffff81155f65:       9c                      pushfq
>> ffffffff81155f66:       41 5c                   pop    %r12
>> ffffffff81155f68:       fa                      cli
>> ffffffff81155f69:       e8 72 5c fd ff          callq  ffffffff8112bbe0
>> <trace_hardirqs_off>
>> ffffffff81155f6e:       4c 8d 6b 50             lea    0x50(%rbx),%r13
>> ffffffff81155f72:       45 31 c9                xor    %r9d,%r9d
>> ffffffff81155f75:       31 c9                   xor    %ecx,%ecx
>> ffffffff81155f77:       31 d2                   xor    %edx,%edx
>> ffffffff81155f79:       31 f6                   xor    %esi,%esi
>> ffffffff81155f7b:       4c 89 ef                mov    %r13,%rdi
>> ffffffff81155f7e:       48 c7 04 24 55 5f 15    movq
>> $0xffffffff81155f55,(%rsp)
>> ffffffff81155f85:       81
>> ffffffff81155f86:       41 b8 01 00 00 00       mov    $0x1,%r8d
>> ffffffff81155f8c:       e8 3f b3 fd ff          callq  ffffffff811312d0
>> <lock_acquire>
>> ffffffff81155f91:       48 c7 c2 55 5f 15 81    mov
>> $0xffffffff81155f55,%rdx
>> ffffffff81155f98:       be 01 00 00 00          mov    $0x1,%esi
>> ffffffff81155f9d:       4c 89 ef                mov    %r13,%rdi
>> ffffffff81155fa0:       e8 0b b5 fd ff          callq  ffffffff811314b0
>> <lock_release>
>> ffffffff81155fa5:       41 f7 c4 00 02 00 00    test   $0x200,%r12d
>> ffffffff81155fac:       75 52                   jne    ffffffff81156000
>> <del_timer_sync+0xb0>
>> ffffffff81155fae:       41 54                   push   %r12
>> ffffffff81155fb0:       9d                      popfq
>> ffffffff81155fb1:       e8 2a 5c fd ff          callq  ffffffff8112bbe0
>> <trace_hardirqs_off>
>> ffffffff81155fb6:       65 8b 05 5b 66 eb 7e    mov
>> %gs:0x7eeb665b(%rip),%eax        # c618 <__preempt_count>
>> ffffffff81155fbd:       a9 00 00 0f 00          test   $0xf0000,%eax
>> ffffffff81155fc2:       74 25                   je     ffffffff81155fe9
>> <del_timer_sync+0x99>
>> ffffffff81155fc4:       f6 43 2a 20             testb  $0x20,0x2a(%rbx)
>> ffffffff81155fc8:       75 1f                   jne    ffffffff81155fe9
>> <del_timer_sync+0x99>
>> ffffffff81155fca:       be 61 04 00 00          mov    $0x461,%esi
>> ffffffff81155fcf:       48 c7 c7 09 87 f3 81    mov
>> $0xffffffff81f38709,%rdi
>> ffffffff81155fd6:       e8 15 03 f8 ff          callq  ffffffff810d62f0
>> <warn_slowpath_null>
>> ffffffff81155fdb:       48 89 df                mov    %rbx,%rdi
>> ffffffff81155fde:       e8 fd fe ff ff          callq  ffffffff81155ee0
>> <try_to_del_timer_sync>
>> ffffffff81155fe3:       85 c0                   test   %eax,%eax
>> ffffffff81155fe5:       79 0e                   jns    ffffffff81155ff5
>> <del_timer_sync+0xa5>
>> ffffffff81155fe7:       f3 90                   pause
>> ffffffff81155fe9:       48 89 df                mov    %rbx,%rdi
>> ffffffff81155fec:       e8 ef fe ff ff          callq  ffffffff81155ee0
>> <try_to_del_timer_sync>
>> ffffffff81155ff1:       85 c0                   test   %eax,%eax
>> ffffffff81155ff3:       78 f2                   js     ffffffff81155fe7
>> <del_timer_sync+0x97>
>> ffffffff81155ff5:       48 83 c4 08             add    $0x8,%rsp
>> ffffffff81155ff9:       5b                      pop    %rbx
>> ffffffff81155ffa:       41 5c                   pop    %r12
>> ffffffff81155ffc:       41 5d                   pop    %r13
>> ffffffff81155ffe:       5d                      pop    %rbp
>> ffffffff81155fff:       c3                      retq
>> ffffffff81156000:       e8 4b 8b fd ff          callq  ffffffff8112eb50
>> <trace_hardirqs_on>
>> ffffffff81156005:       41 54                   push   %r12
>> ffffffff81156007:       9d                      popfq
>> ffffffff81156008:       eb ac                   jmp    ffffffff81155fb6
>> <del_timer_sync+0x66>
>> ffffffff8115600a:       66 0f 1f 44 00 00       nopw   0x0(%rax,%rax,1)
>>
>
> OK, I cannot say much to your analysis.
>
> The full make-lines look differently.
>
> GCC for example has '-mfentry -DCC_USING_FENTRY'.
>
> [ CLANG ]
>
> mycompiler -Wp,-MD,kernel/.workqueue.o.d  -nostdinc -isystem
> /opt/llvm-toolchain-3.8.0rc3/bin/../lib/clang/3.8.0/include -nostdinc
> -isystem /opt/llvm-toolchain-3.8.0rc3/bin/../lib/clang/3.8.0/include
> -I./arch/x86/include -Iarch/x86/include/generated/uapi
> -Iarch/x86/include/generated  -Iinclude -I./arch/x86/include/uapi
> -Iarch/x86/include/generated/uapi -I./include/uapi
> -Iinclude/generated/uapi -include ./include/linux/kconfig.h
> -D__KERNEL__ -Qunused-arguments -Wno-unknown-warning-option -Wall
> -Wundef -Wstrict-prototypes -Wno-trigraphs -fno-strict-aliasing
> -fno-common -Werror-implicit-function-declaration -Wno-format-security
> -std=gnu89 -no-integrated-as -mno-sse -mno-mmx -mno-sse2 -mno-3dnow
> -mno-avx -m64 -mtune=generic -mno-red-zone -mcmodel=kernel
> -funit-at-a-time -DCONFIG_X86_X32_ABI -DCONFIG_AS_CFI=1
> -DCONFIG_AS_CFI_SIGNAL_FRAME=1 -DCONFIG_AS_CFI_SECTIONS=1
> -DCONFIG_AS_FXSAVEQ=1 -DCONFIG_AS_SSSE3=1 -DCONFIG_AS_CRC32=1
> -DCONFIG_AS_AVX=1 -DCONFIG_AS_AVX2=1 -pipe -Wno-sign-compare
> -fno-asynchronous-unwind-tables -O2 -Wframe-larger-than=1024
> -fno-stack-protector -Wno-unused-variable
> -Wno-format-invalid-specifier -Wno-gnu -Wno-asm-operand-widths
> -Wno-initializer-overrides -fno-builtin -Wno-tautological-compare
> -mno-global-merge -fno-omit-frame-pointer -fno-optimize-sibling-calls
> -pg -Wdeclaration-after-statement -Wno-pointer-sign
> -fno-strict-overflow -Werror=implicit-int -Werror=strict-prototypes
> -Werror=date-time -Wno-initializer-overrides -Wno-unused-value
> -Wno-format -Wno-unknown-warning-option -Wno-sign-compare
> -Wno-format-zero-length -Wno-uninitialized    -D"KBUILD_STR(s)=#s"
> -D"KBUILD_BASENAME=KBUILD_STR(workqueue)"
> -D"KBUILD_MODNAME=KBUILD_STR(workqueue)" -c -o kernel/.tmp_workqueue.o
> kernel/workqueue.c
>
> mycompiler -Wp,-MD,kernel/time/.timer.o.d  -nostdinc -isystem
> /opt/llvm-toolchain-3.8.0rc3/bin/../lib/clang/3.8.0/include -nostdinc
> -isystem /opt/llvm-toolchain-3.8.0rc3/bin/../lib/clang/3.8.0/include
> -I./arch/x86/include -Iarch/x86/include/generated/uapi
> -Iarch/x86/include/generated  -Iinclude -I./arch/x86/include/uapi
> -Iarch/x86/include/generated/uapi -I./include/uapi
> -Iinclude/generated/uapi -include ./include/linux/kconfig.h
> -D__KERNEL__ -Qunused-arguments -Wno-unknown-warning-option -Wall
> -Wundef -Wstrict-prototypes -Wno-trigraphs -fno-strict-aliasing
> -fno-common -Werror-implicit-function-declaration -Wno-format-security
> -std=gnu89 -no-integrated-as -mno-sse -mno-mmx -mno-sse2 -mno-3dnow
> -mno-avx -m64 -mtune=generic -mno-red-zone -mcmodel=kernel
> -funit-at-a-time -DCONFIG_X86_X32_ABI -DCONFIG_AS_CFI=1
> -DCONFIG_AS_CFI_SIGNAL_FRAME=1 -DCONFIG_AS_CFI_SECTIONS=1
> -DCONFIG_AS_FXSAVEQ=1 -DCONFIG_AS_SSSE3=1 -DCONFIG_AS_CRC32=1
> -DCONFIG_AS_AVX=1 -DCONFIG_AS_AVX2=1 -pipe -Wno-sign-compare
> -fno-asynchronous-unwind-tables -O2 -Wframe-larger-than=1024
> -fno-stack-protector -Wno-unused-variable
> -Wno-format-invalid-specifier -Wno-gnu -Wno-asm-operand-widths
> -Wno-initializer-overrides -fno-builtin -Wno-tautological-compare
> -mno-global-merge -fno-omit-frame-pointer -fno-optimize-sibling-calls
> -pg -Wdeclaration-after-statement -Wno-pointer-sign
> -fno-strict-overflow -Werror=implicit-int -Werror=strict-prototypes
> -Werror=date-time -Wno-initializer-overrides -Wno-unused-value
> -Wno-format -Wno-unknown-warning-option -Wno-sign-compare
> -Wno-format-zero-length -Wno-uninitialized    -D"KBUILD_STR(s)=#s"
> -D"KBUILD_BASENAME=KBUILD_STR(timer)"
> -D"KBUILD_MODNAME=KBUILD_STR(timer)" -c -o kernel/time/.tmp_timer.o
> kernel/time/timer.c
>
> [ GCC ]
>
> mycompiler -Wp,-MD,kernel/.workqueue.o.d  -nostdinc -isystem
> /usr/lib/gcc/x86_64-linux-gnu/4.9/include -nostdinc -isystem
> /usr/lib/gcc/x86_64-linux-gnu/4.9/include -I./arch/x86/include
> -Iarch/x86/include/generated/uapi -Iarch/x86/include/generated
> -Iinclude -I./arch/x86/include/uapi -Iarch/x86/include/generated/uapi
> -I./include/uapi -Iinclude/generated/uapi -include
> ./include/linux/kconfig.h -D__KERNEL__ -Wall -Wundef
> -Wstrict-prototypes -Wno-trigraphs -fno-strict-aliasing -fno-common
> -Werror-implicit-function-declaration -Wno-format-security -std=gnu89
> -mno-sse -mno-mmx -mno-sse2 -mno-3dnow -mno-avx -m64 -falign-jumps=1
> -falign-loops=1 -mno-80387 -mno-fp-ret-in-387
> -mpreferred-stack-boundary=3 -mtune=generic -mno-red-zone
> -mcmodel=kernel -funit-at-a-time -maccumulate-outgoing-args
> -DCONFIG_X86_X32_ABI -DCONFIG_AS_CFI=1 -DCONFIG_AS_CFI_SIGNAL_FRAME=1
> -DCONFIG_AS_CFI_SECTIONS=1 -DCONFIG_AS_FXSAVEQ=1 -DCONFIG_AS_SSSE3=1
> -DCONFIG_AS_CRC32=1 -DCONFIG_AS_AVX=1 -DCONFIG_AS_AVX2=1 -pipe
> -Wno-sign-compare -fno-asynchronous-unwind-tables
> -fno-delete-null-pointer-checks -O2 --param=allow-store-data-races=0
> -Wframe-larger-than=1024 -fno-stack-protector
> -Wno-unused-but-set-variable -fno-omit-frame-pointer
> -fno-optimize-sibling-calls -fno-var-tracking-assignments -pg -mfentry
> -DCC_USING_FENTRY -Wdeclaration-after-statement -Wno-pointer-sign
> -fno-strict-overflow -fconserve-stack -Werror=implicit-int
> -Werror=strict-prototypes -Werror=date-time -DCC_HAVE_ASM_GOTO
> -D"KBUILD_STR(s)=#s" -D"KBUILD_BASENAME=KBUILD_STR(workqueue)"
> -D"KBUILD_MODNAME=KBUILD_STR(workqueue)" -c -o kernel/.tmp_workqueue.o
> kernel/workqueue.c
>
> mycompiler -Wp,-MD,kernel/time/.timer.o.d  -nostdinc -isystem
> /usr/lib/gcc/x86_64-linux-gnu/4.9/include -nostdinc -isystem
> /usr/lib/gcc/x86_64-linux-gnu/4.9/include -I./arch/x86/include
> -Iarch/x86/include/generated/uapi -Iarch/x86/include/generated
> -Iinclude -I./arch/x86/include/uapi -Iarch/x86/include/generated/uapi
> -I./include/uapi -Iinclude/generated/uapi -include
> ./include/linux/kconfig.h -D__KERNEL__ -Wall -Wundef
> -Wstrict-prototypes -Wno-trigraphs -fno-strict-aliasing -fno-common
> -Werror-implicit-function-declaration -Wno-format-security -std=gnu89
> -mno-sse -mno-mmx -mno-sse2 -mno-3dnow -mno-avx -m64 -falign-jumps=1
> -falign-loops=1 -mno-80387 -mno-fp-ret-in-387
> -mpreferred-stack-boundary=3 -mtune=generic -mno-red-zone
> -mcmodel=kernel -funit-at-a-time -maccumulate-outgoing-args
> -DCONFIG_X86_X32_ABI -DCONFIG_AS_CFI=1 -DCONFIG_AS_CFI_SIGNAL_FRAME=1
> -DCONFIG_AS_CFI_SECTIONS=1 -DCONFIG_AS_FXSAVEQ=1 -DCONFIG_AS_SSSE3=1
> -DCONFIG_AS_CRC32=1 -DCONFIG_AS_AVX=1 -DCONFIG_AS_AVX2=1 -pipe
> -Wno-sign-compare -fno-asynchronous-unwind-tables
> -fno-delete-null-pointer-checks -O2 --param=allow-store-data-races=0
> -Wframe-larger-than=1024 -fno-stack-protector
> -Wno-unused-but-set-variable -fno-omit-frame-pointer
> -fno-optimize-sibling-calls -fno-var-tracking-assignments -pg -mfentry
> -DCC_USING_FENTRY -Wdeclaration-after-statement -Wno-pointer-sign
> -fno-strict-overflow -fconserve-stack -Werror=implicit-int
> -Werror=strict-prototypes -Werror=date-time -DCC_HAVE_ASM_GOTO
> -D"KBUILD_STR(s)=#s" -D"KBUILD_BASENAME=KBUILD_STR(timer)"
> -D"KBUILD_MODNAME=KBUILD_STR(timer)" -c -o kernel/time/.tmp_timer.o
> kernel/time/timer.c
>
> I can try to use the make-line of GCC and re-compile.
>

Look here...

+ mycompiler -Wp,-MD,kernel/time/.timer.o.d -nostdinc -isystem
/usr/lib/gcc/x86_64-linux-gnu/4.9/include -nostdinc -isystem
/usr/lib/gcc/x86_64-linux-gnu/4.9/include -I./arch/x86/include
-Iarch/x86/include/generated/uapi -Iarch/x86/include/generated
-Iinclude -I./arch/x86/include/uapi -Iarch/x86/include/generated/uapi
-I./include/uapi -Iinclude/generated/uapi -include
./include/linux/kconfig.h -D__KERNEL__ -Wall -Wundef
-Wstrict-prototypes -Wno-trigraphs -fno-strict-aliasing -fno-common
-Werror-implicit-function-declaration -Wno-format-security -std=gnu89
-mno-sse -mno-mmx -mno-sse2 -mno-3dnow -mno-avx -m64 -falign-jumps=1
-falign-loops=1 -mno-80387 -mno-fp-ret-in-387
-mpreferred-stack-boundary=3 -mtune=generic -mno-red-zone
-mcmodel=kernel -funit-at-a-time -maccumulate-outgoing-args
-DCONFIG_X86_X32_ABI -DCONFIG_AS_CFI=1 -DCONFIG_AS_CFI_SIGNAL_FRAME=1
-DCONFIG_AS_CFI_SECTIONS=1 -DCONFIG_AS_FXSAVEQ=1 -DCONFIG_AS_SSSE3=1
-DCONFIG_AS_CRC32=1 -DCONFIG_AS_AVX=1 -DCONFIG_AS_AVX2=1 -pipe
-Wno-sign-compare -fno-asynchronous-unwind-tables
-fno-delete-null-pointer-checks -O2 --param=allow-store-data-races=0
-Wframe-larger-than=1024 -fno-stack-protector
-Wno-unused-but-set-variable -fno-omit-frame-pointer
-fno-optimize-sibling-calls -fno-var-tracking-assignments -pg -mfentry
-DCC_USING_FENTRY -Wdeclaration-after-statement -Wno-pointer-sign
-fno-strict-overflow -fconserve-stack -Werror=implicit-int
-Werror=strict-prototypes -Werror=date-time -DCC_HAVE_ASM_GOTO
-DKBUILD_STR(s)=#s -DKBUILD_BASENAME=KBUILD_STR(timer)
-DKBUILD_MODNAME=KBUILD_STR(timer) -c -o kernel/time/.tmp_timer.o
kernel/time/timer.c
clang-3.8: error: unknown argument: '-mno-80387'
clang-3.8: error: unknown argument: '-mno-fp-ret-in-387'
clang-3.8: error: unknown argument: '-mpreferred-stack-boundary=3'
clang-3.8: error: unknown argument: '-maccumulate-outgoing-args'
clang-3.8: error: unknown argument: '-fno-var-tracking-assignments'
clang-3.8: error: unknown argument: '-mfentry'
clang-3.8: error: unknown argument: '-fconserve-stack'
clang-3.8: warning: optimization flag '-falign-jumps=1' is not supported
clang-3.8: warning: optimization flag '-falign-loops=1' is not supported
clang-3.8: warning: optimization flag
'-fno-delete-null-pointer-checks' is not supported
+ ld -m elf_x86_64 -r kernel/time/.tmp_timer.o -o kernel/time/timer.o
ld: cannot find kernel/time/.tmp_timer.o: No such file or directory

- Sedat -

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