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Groups > linux.kernel > #1242842 > unrolled thread
| Started by | "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> |
|---|---|
| First post | 2015-10-09 02:00 +0200 |
| Last post | 2015-10-09 19:10 +0200 |
| Articles | 3 — 3 participants |
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Re: [v3 PATCH] arm64: replace read_lock to rcu lock in call_break_hook "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2015-10-09 02:00 +0200
Re: [v3 PATCH] arm64: replace read_lock to rcu lock in call_break_hook Will Deacon <will.deacon@arm.com> - 2015-10-09 11:10 +0200
Re: [v3 PATCH] arm64: replace read_lock to rcu lock in call_break_hook Steven Rostedt <rostedt@goodmis.org> - 2015-10-09 19:10 +0200
| From | "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> |
|---|---|
| Date | 2015-10-09 02:00 +0200 |
| Subject | Re: [v3 PATCH] arm64: replace read_lock to rcu lock in call_break_hook |
| Message-ID | <qhtgm-1Ro-11@gated-at.bofh.it> |
On Mon, Oct 05, 2015 at 02:32:51PM -0700, Yang Shi wrote:
> BUG: sleeping function called from invalid context at kernel/locking/rtmutex.c:917
> in_atomic(): 0, irqs_disabled(): 128, pid: 342, name: perf
> 1 lock held by perf/342:
> #0: (break_hook_lock){+.+...}, at: [<ffffffc0000851ac>] call_break_hook+0x34/0xd0
> irq event stamp: 62224
> hardirqs last enabled at (62223): [<ffffffc00010b7bc>] __call_rcu.constprop.59+0x104/0x270
> hardirqs last disabled at (62224): [<ffffffc0000fbe20>] vprintk_emit+0x68/0x640
> softirqs last enabled at (0): [<ffffffc000097928>] copy_process.part.8+0x428/0x17f8
> softirqs last disabled at (0): [< (null)>] (null)
> CPU: 0 PID: 342 Comm: perf Not tainted 4.1.6-rt5 #4
> Hardware name: linux,dummy-virt (DT)
> Call trace:
> [<ffffffc000089968>] dump_backtrace+0x0/0x128
> [<ffffffc000089ab0>] show_stack+0x20/0x30
> [<ffffffc0007030d0>] dump_stack+0x7c/0xa0
> [<ffffffc0000c878c>] ___might_sleep+0x174/0x260
> [<ffffffc000708ac8>] __rt_spin_lock+0x28/0x40
> [<ffffffc000708db0>] rt_read_lock+0x60/0x80
> [<ffffffc0000851a8>] call_break_hook+0x30/0xd0
> [<ffffffc000085a70>] brk_handler+0x30/0x98
> [<ffffffc000082248>] do_debug_exception+0x50/0xb8
> Exception stack(0xffffffc00514fe30 to 0xffffffc00514ff50)
> fe20: 00000000 00000000 c1594680 0000007f
> fe40: ffffffff ffffffff 92063940 0000007f 0550dcd8 ffffffc0 00000000 00000000
> fe60: 0514fe70 ffffffc0 000be1f8 ffffffc0 0514feb0 ffffffc0 0008948c ffffffc0
> fe80: 00000004 00000000 0514fed0 ffffffc0 ffffffff ffffffff 9282a948 0000007f
> fea0: 00000000 00000000 9282b708 0000007f c1592820 0000007f 00083914 ffffffc0
> fec0: 00000000 00000000 00000010 00000000 00000064 00000000 00000001 00000000
> fee0: 005101e0 00000000 c1594680 0000007f c1594740 0000007f ffffffd8 ffffff80
> ff00: 00000000 00000000 00000000 00000000 c1594770 0000007f c1594770 0000007f
> ff20: 00665e10 00000000 7f7f7f7f 7f7f7f7f 01010101 01010101 00000000 00000000
> ff40: 928e4cc0 0000007f 91ff11e8 0000007f
>
> call_break_hook is called in atomic context (hard irq disabled), so replace
> the sleepable lock to rcu lock, replace relevant list operations to rcu
> version and call synchronize_rcu() in unregister_break_hook().
>
> And, replace write lock to spinlock in {un}register_break_hook.
>
> Signed-off-by: Yang Shi <yang.shi@linaro.org>
Looks more plausible to me. Does it look OK to you, Steven?
Thanx, Paul
> ---
> v2 -> v3
> Add synchronize_rcu() in ungister_break_hook()
> Replace write lock to spinlock
>
> v1 -> v2
> Replace list operations to rcu version.
>
> arch/arm64/kernel/debug-monitors.c | 21 +++++++++++----------
> 1 file changed, 11 insertions(+), 10 deletions(-)
>
> diff --git a/arch/arm64/kernel/debug-monitors.c b/arch/arm64/kernel/debug-monitors.c
> index cebf786..13ca9cd 100644
> --- a/arch/arm64/kernel/debug-monitors.c
> +++ b/arch/arm64/kernel/debug-monitors.c
> @@ -271,20 +271,21 @@ static int single_step_handler(unsigned long addr, unsigned int esr,
> * Use reader/writer locks instead of plain spinlock.
> */
> static LIST_HEAD(break_hook);
> -static DEFINE_RWLOCK(break_hook_lock);
> +static DEFINE_SPINLOCK(break_hook_lock);
>
> void register_break_hook(struct break_hook *hook)
> {
> - write_lock(&break_hook_lock);
> - list_add(&hook->node, &break_hook);
> - write_unlock(&break_hook_lock);
> + spin_lock(&break_hook_lock);
> + list_add_rcu(&hook->node, &break_hook);
> + spin_unlock(&break_hook_lock);
> }
>
> void unregister_break_hook(struct break_hook *hook)
> {
> - write_lock(&break_hook_lock);
> - list_del(&hook->node);
> - write_unlock(&break_hook_lock);
> + spin_lock(&break_hook_lock);
> + list_del_rcu(&hook->node);
> + spin_unlock(&break_hook_lock);
> + synchronize_rcu();
> }
>
> static int call_break_hook(struct pt_regs *regs, unsigned int esr)
> @@ -292,11 +293,11 @@ static int call_break_hook(struct pt_regs *regs, unsigned int esr)
> struct break_hook *hook;
> int (*fn)(struct pt_regs *regs, unsigned int esr) = NULL;
>
> - read_lock(&break_hook_lock);
> - list_for_each_entry(hook, &break_hook, node)
> + rcu_read_lock();
> + list_for_each_entry_rcu(hook, &break_hook, node)
> if ((esr & hook->esr_mask) == hook->esr_val)
> fn = hook->fn;
> - read_unlock(&break_hook_lock);
> + rcu_read_unlock();
>
> return fn ? fn(regs, esr) : DBG_HOOK_ERROR;
> }
> --
> 2.0.2
>
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| From | Will Deacon <will.deacon@arm.com> |
|---|---|
| Date | 2015-10-09 11:10 +0200 |
| Message-ID | <qhBQC-63L-21@gated-at.bofh.it> |
| In reply to | #1242842 |
On Thu, Oct 08, 2015 at 04:55:38PM -0700, Paul E. McKenney wrote:
> On Mon, Oct 05, 2015 at 02:32:51PM -0700, Yang Shi wrote:
> > BUG: sleeping function called from invalid context at kernel/locking/rtmutex.c:917
> > in_atomic(): 0, irqs_disabled(): 128, pid: 342, name: perf
> > 1 lock held by perf/342:
> > #0: (break_hook_lock){+.+...}, at: [<ffffffc0000851ac>] call_break_hook+0x34/0xd0
> > irq event stamp: 62224
> > hardirqs last enabled at (62223): [<ffffffc00010b7bc>] __call_rcu.constprop.59+0x104/0x270
> > hardirqs last disabled at (62224): [<ffffffc0000fbe20>] vprintk_emit+0x68/0x640
> > softirqs last enabled at (0): [<ffffffc000097928>] copy_process.part.8+0x428/0x17f8
> > softirqs last disabled at (0): [< (null)>] (null)
> > CPU: 0 PID: 342 Comm: perf Not tainted 4.1.6-rt5 #4
> > Hardware name: linux,dummy-virt (DT)
> > Call trace:
> > [<ffffffc000089968>] dump_backtrace+0x0/0x128
> > [<ffffffc000089ab0>] show_stack+0x20/0x30
> > [<ffffffc0007030d0>] dump_stack+0x7c/0xa0
> > [<ffffffc0000c878c>] ___might_sleep+0x174/0x260
> > [<ffffffc000708ac8>] __rt_spin_lock+0x28/0x40
> > [<ffffffc000708db0>] rt_read_lock+0x60/0x80
> > [<ffffffc0000851a8>] call_break_hook+0x30/0xd0
> > [<ffffffc000085a70>] brk_handler+0x30/0x98
> > [<ffffffc000082248>] do_debug_exception+0x50/0xb8
> > Exception stack(0xffffffc00514fe30 to 0xffffffc00514ff50)
> > fe20: 00000000 00000000 c1594680 0000007f
> > fe40: ffffffff ffffffff 92063940 0000007f 0550dcd8 ffffffc0 00000000 00000000
> > fe60: 0514fe70 ffffffc0 000be1f8 ffffffc0 0514feb0 ffffffc0 0008948c ffffffc0
> > fe80: 00000004 00000000 0514fed0 ffffffc0 ffffffff ffffffff 9282a948 0000007f
> > fea0: 00000000 00000000 9282b708 0000007f c1592820 0000007f 00083914 ffffffc0
> > fec0: 00000000 00000000 00000010 00000000 00000064 00000000 00000001 00000000
> > fee0: 005101e0 00000000 c1594680 0000007f c1594740 0000007f ffffffd8 ffffff80
> > ff00: 00000000 00000000 00000000 00000000 c1594770 0000007f c1594770 0000007f
> > ff20: 00665e10 00000000 7f7f7f7f 7f7f7f7f 01010101 01010101 00000000 00000000
> > ff40: 928e4cc0 0000007f 91ff11e8 0000007f
> >
> > call_break_hook is called in atomic context (hard irq disabled), so replace
> > the sleepable lock to rcu lock, replace relevant list operations to rcu
> > version and call synchronize_rcu() in unregister_break_hook().
> >
> > And, replace write lock to spinlock in {un}register_break_hook.
> >
> > Signed-off-by: Yang Shi <yang.shi@linaro.org>
>
> Looks more plausible to me. Does it look OK to you, Steven?
This is already in mainline as a fix, so please shout loudly if you think
it's broken (it looked ok to me and didn't cause any regressions in my
testing).
Will
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| From | Steven Rostedt <rostedt@goodmis.org> |
|---|---|
| Date | 2015-10-09 19:10 +0200 |
| Message-ID | <qhJl8-8pE-25@gated-at.bofh.it> |
| In reply to | #1243165 |
On Fri, 9 Oct 2015 10:05:50 +0100 Will Deacon <will.deacon@arm.com> wrote: > > Looks more plausible to me. Does it look OK to you, Steven? > > This is already in mainline as a fix, so please shout loudly if you think > it's broken (it looked ok to me and didn't cause any regressions in my > testing). Looks good to me. -- Steve -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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