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Re: [PATCH v4] lib/spinlock_debug.c: prevent a recursive cycle in the debug code

From Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
Newsgroups linux.kernel
Subject Re: [PATCH v4] lib/spinlock_debug.c: prevent a recursive cycle in the debug code
Date 2016-01-29 07:20 +0100
Message-ID <qWazw-72K-3@gated-at.bofh.it> (permalink)
References (5 earlier) <qW3Ro-28Y-31@gated-at.bofh.it> <qW56P-2Vm-3@gated-at.bofh.it> <qW90K-5NS-7@gated-at.bofh.it> <qW9N8-6pA-7@gated-at.bofh.it> <qWa6u-6yI-3@gated-at.bofh.it>
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On (01/28/16 21:48), Peter Hurley wrote:
[..]
> > yes, I proposed to add a ->reset callback to struct console
> > a while ago, and to do a console reset loop in zap_locks()
> 
> What was the patch series title? I'd like to review that.

Thanks.

it was deep in the thread where Jan Kara proposed v1 of his
printk offloading support
"Re: [PATCH 1/7] printk: Hand over printing to console if printing too long"

 http://marc.info/?l=linux-kernel&m=144976121529901

I never ended up sending this out as a separate patch. my bad.

the panic()->zap_locks() was here (well, not even a patch set):
 http://marc.info/?l=linux-kernel&m=145260677129044

> That would solve the recursive deadlock from console driver as well
> (at least with CONFIG_DEBUG_SPINLOCK) because the printk() recursion
> would zap the locks including the console driver's lock and
> at least get the last output so that we'd know there was a recursion,
> and fix it.

yes, if printk() has a chance to detect a recursion and invoke zap_locks()
(which is based on logbuf_cpu check). in my other email there is a scenario
when printk() has no such a chance -- because 'logbuf_cpu' is set to UINT_MAX
right before raw_spin_unlock(&logbuf_lock). and if debug_spin_unlock() detects
a coding error (not even a corruption) (->owner != current, or
->owner_cpu != raw_smp_processor_id()) then things are turning bad quickly.

mail: http://marc.info/?l=linux-kernel&m=145404023915268

	-ss

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Re: [PATCH v4] lib/spinlock_debug.c: prevent a recursive cycle in  the debug code Byungchul Park <byungchul.park@lge.com> - 2016-01-28 03:00 +0100
  Re: [PATCH v4] lib/spinlock_debug.c: prevent a recursive cycle in  the debug code Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2016-01-28 03:40 +0100
    RE: [PATCH v4] lib/spinlock_debug.c: prevent a recursive cycle in the debug code "byungchul.park" <byungchul.park@lge.com> - 2016-01-28 06:00 +0100
      Re: [PATCH v4] lib/spinlock_debug.c: prevent a recursive cycle in  the debug code Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2016-01-28 07:10 +0100
        Re: [PATCH v4] lib/spinlock_debug.c: prevent a recursive cycle in  the debug code Byungchul Park <byungchul.park@lge.com> - 2016-01-28 09:30 +0100
          Re: [PATCH v4] lib/spinlock_debug.c: prevent a recursive cycle in  the debug code Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2016-01-28 11:50 +0100
            Re: [PATCH v4] lib/spinlock_debug.c: prevent a recursive cycle in  the debug code Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2016-01-28 12:00 +0100
              Re: [PATCH v4] lib/spinlock_debug.c: prevent a recursive cycle in  the debug code Sergey Senozhatsky <sergey.senozhatsky@gmail.com> - 2016-01-28 16:50 +0100
                Re: [PATCH v4] lib/spinlock_debug.c: prevent a recursive cycle in the  debug code Peter Hurley <peter@hurleysoftware.com> - 2016-01-29 00:10 +0100
                Re: [PATCH v4] lib/spinlock_debug.c: prevent a recursive cycle in  the debug code Byungchul Park <byungchul.park@lge.com> - 2016-01-29 01:00 +0100
                Re: [PATCH v4] lib/spinlock_debug.c: prevent a recursive cycle in  the debug code Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2016-01-29 02:00 +0100
                Re: [PATCH v4] lib/spinlock_debug.c: prevent a recursive cycle in  the debug code Byungchul Park <byungchul.park@lge.com> - 2016-01-29 04:10 +0100
                Re: [PATCH v4] lib/spinlock_debug.c: prevent a recursive cycle in  the debug code Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2016-01-29 05:10 +0100
                Re: [PATCH v4] lib/spinlock_debug.c: prevent a recursive cycle in  the debug code Byungchul Park <byungchul.park@lge.com> - 2016-01-29 13:20 +0100
                Re: [PATCH v4] lib/spinlock_debug.c: prevent a recursive cycle in  the debug code Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2016-01-29 01:30 +0100
                Re: [PATCH v4] lib/spinlock_debug.c: prevent a recursive cycle in the  debug code Peter Hurley <peter@hurleysoftware.com> - 2016-01-29 05:40 +0100
                Re: [PATCH v4] lib/spinlock_debug.c: prevent a recursive cycle in  the debug code Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2016-01-29 06:30 +0100
                Re: [PATCH v4] lib/spinlock_debug.c: prevent a recursive cycle in the  debug code Peter Hurley <peter@hurleysoftware.com> - 2016-01-29 06:50 +0100
                Re: [PATCH v4] lib/spinlock_debug.c: prevent a recursive cycle in  the debug code Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2016-01-29 07:20 +0100
                Re: [PATCH v4] lib/spinlock_debug.c: prevent a recursive cycle in  the debug code Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2016-01-29 07:40 +0100
                Re: [PATCH v4] lib/spinlock_debug.c: prevent a recursive cycle in  the debug code Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2016-01-31 13:30 +0100
                [PATCH 2/3] printk: introduce reset_console_drivers() Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2016-01-31 13:40 +0100
                Re: [PATCH 2/3] printk: introduce reset_console_drivers() kbuild test robot <lkp@intel.com> - 2016-01-31 13:50 +0100
                [PATCH 1/3] printk: introduce console_reset_on_panic() function Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2016-01-31 13:40 +0100
                [PATCH 3/3] spinlock_debug: panic on recursive lock spin_dump() Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2016-01-31 13:40 +0100
                Re: [PATCH 3/3] spinlock_debug: panic on recursive lock spin_dump() Sergey Senozhatsky <sergey.senozhatsky@gmail.com> - 2016-02-01 17:20 +0100
                Re: [PATCH 3/3] spinlock_debug: panic on recursive lock spin_dump() Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2016-02-02 09:00 +0100
                Re: [PATCH 1/3] printk: introduce console_reset_on_panic() function kbuild test robot <lkp@intel.com> - 2016-01-31 13:50 +0100
                Re: [PATCH v4] lib/spinlock_debug.c: prevent a recursive cycle in  the debug code Byungchul Park <byungchul.park@lge.com> - 2016-01-29 08:00 +0100
                Re: [PATCH v4] lib/spinlock_debug.c: prevent a recursive cycle in  the debug code Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2016-01-29 08:20 +0100
                Re: [PATCH v4] lib/spinlock_debug.c: prevent a recursive cycle in  the debug code Byungchul Park <byungchul.park@lge.com> - 2016-01-29 09:20 +0100

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