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Date: Wed, 9 Apr 2014 15:19:40 +0300
From: "Kirill A. Shutemov" <kirill@...temov.name>
To: "Michael L. Semon" <mlsemon35@...il.com>,
Ingo Molnar <mingo@...nel.org>,
Peter Zijlstra <peterz@...radead.org>, jason.low2@...com
Cc: linux-kernel@...r.kernel.org
Subject: Re: 3.14.0+/x86: lockdep and mutexes not getting along
On Sun, Apr 06, 2014 at 01:12:14AM -0400, Michael L. Semon wrote:
> Hi! Starting early in this merge window for 3.15, lockdep has been
> giving me trouble. Normally, a splat will happen, lockdep will shut
> itself off, and my i686 Pentium 4 PC will continue. Now, after the
> splat, it will allow one key of input at either a VGA console or over
> serial. After that, only the magic SysRq keys and KDB still work.
> File activity stops, and many processes are stuck in the D state.
>
> Bisect brought me here:
>
> root@...earer:/usr/src/kernel-git/linux# git bisect good
> 6f008e72cd111a119b5d8de8c5438d892aae99eb is the first bad commit
> commit 6f008e72cd111a119b5d8de8c5438d892aae99eb
> Author: Peter Zijlstra <peterz@...radead.org>
> Date: Wed Mar 12 13:24:42 2014 +0100
>
> locking/mutex: Fix debug checks
>
> OK, so commit:
>
> 1d8fe7dc8078 ("locking/mutexes: Unlock the mutex without the wait_lock")
>
> generates this boot warning when CONFIG_DEBUG_MUTEXES=y:
>
> WARNING: CPU: 0 PID: 139 at /usr/src/linux-2.6/kernel/locking/mutex-debug.c:82 debug_mutex_unlock+0x155/0x180() DEBUG_LOCKS_WARN_ON(lock->owner != current)
>
> And that makes sense, because as soon as we release the lock a
> new owner can come in...
>
> One would think that !__mutex_slowpath_needs_to_unlock()
> implementations suffer the same, but for DEBUG we fall back to
> mutex-null.h which has an unconditional 1 for that.
>
> The mutex debug code requires the mutex to be unlocked after
> doing the debug checks, otherwise it can find inconsistent
> state.
>
> Reported-by: Ingo Molnar <mingo@...nel.org>
> Signed-off-by: Peter Zijlstra <peterz@...radead.org>
> Cc: jason.low2@...com
> Link: http://lkml.kernel.org/r/20140312122442.GB27965@twins.programming.kicks-ass.net
> Signed-off-by: Ingo Molnar <mingo@...nel.org>
>
> :040000 040000 80e40c2009942a31f98127c4f9fa958f34b3947b f46ed4b70c4f30fc665fe8f810d3c13920cd765a M kernel
>
> Indeed, my issues are solved (so far) simply by reverting this commit.
>
> Might someone test lockdep on x86 to see if this is a consistent
> issue that needs to be adjusted? My lockdep splats are generated by
> running xfstests test generic/113 on XFS, but splats caused by other
> issues should still create the same symptoms.
>
> Otherwise, this 3.15 kernel has been rather kind to me so far.
>
> PC is an i686 Pentium 4 with 1280 MB RAM and old IDE hardware,
> running Slackware 14.1.
Hi Michael,
+Ingo, +PeterZ and +Jason.
It usually helps to write to relevant people.
I have troble with the commit as well:
[ 26.745741]
[ 26.747484] ======================================================
[ 26.748725] [ INFO: possible circular locking dependency detected ]
[ 26.748725] 3.13.0-11331-g6f008e72cd11 #1162 Not tainted
[ 26.748725] -------------------------------------------------------
[ 26.748725] trinity-c5/848 is trying to acquire lock:
[ 26.748725] (&p->lock){+.+.+.}, at: [<ffffffff811774a8>] seq_read+0x38/0x3c0
[ 26.748725]
[ 26.748725] but task is already holding lock:
[ 26.748725] (&sig->cred_guard_mutex){+.+.+.}, at: [<ffffffff811579db>] prepare_bprm_creds+0x2b/0x80
[ 26.748725]
[ 26.748725] which lock already depends on the new lock.
[ 26.748725]
[ 26.748725]
[ 26.748725] the existing dependency chain (in reverse order) is:
[ 26.748725]
-> #1 (&sig->cred_guard_mutex){+.+.+.}:
[ 26.748725] [<ffffffff810998d8>] __lock_acquire+0x3a8/0xc20
[ 26.748725] [<ffffffff8109a1c6>] lock_acquire+0x76/0xc0
[ 26.748725] [<ffffffff8173634d>] mutex_lock_killable_nested+0x6d/0x460
[ 26.748725] [<ffffffff81049924>] mm_access+0x24/0xb0
[ 26.748725] [<ffffffff811b6307>] m_start+0x67/0x1e0
[ 26.748725] [<ffffffff811775a0>] seq_read+0x130/0x3c0
[ 26.748725] [<ffffffff8114ffaa>] do_loop_readv_writev+0x5a/0x80
[ 26.748725] [<ffffffff81150c4d>] compat_do_readv_writev+0x20d/0x220
[ 26.748725] [<ffffffff81150c92>] compat_readv+0x32/0x70
[ 26.748725] [<ffffffff81151c07>] compat_SyS_readv+0x47/0xa0
[ 26.748725] [<ffffffff81742179>] ia32_sysret+0x0/0x5
[ 26.748725]
-> #0 (&p->lock){+.+.+.}:
[ 26.780481] [<ffffffff81097a4a>] validate_chain.isra.37+0x105a/0x10d0
[ 26.780481] [<ffffffff810998d8>] __lock_acquire+0x3a8/0xc20
[ 26.780481] [<ffffffff8109a1c6>] lock_acquire+0x76/0xc0
[ 26.780481] [<ffffffff81735bad>] mutex_lock_nested+0x6d/0x3d0
[ 26.780481] [<ffffffff811774a8>] seq_read+0x38/0x3c0
[ 26.780481] [<ffffffff811b7af8>] proc_reg_read+0x38/0x70
[ 26.780481] [<ffffffff81150799>] vfs_read+0x99/0x160
[ 26.780481] [<ffffffff8115635c>] kernel_read+0x3c/0x50
[ 26.780481] [<ffffffff811565e7>] prepare_binprm+0x137/0x1d0
[ 26.780481] [<ffffffff81157f82>] do_execve_common.isra.34+0x4d2/0x730
[ 26.780481] [<ffffffff81158461>] SyS_execve+0x31/0x50
[ 26.780481] [<ffffffff81741099>] stub_execve+0x69/0xa0
[ 26.780481]
[ 26.780481] other info that might help us debug this:
[ 26.780481]
[ 26.780481] Possible unsafe locking scenario:
[ 26.780481]
[ 26.780481] CPU0 CPU1
[ 26.780481] ---- ----
[ 26.780481] lock(&sig->cred_guard_mutex);
[ 26.780481] lock(&p->lock);
[ 26.780481] lock(&sig->cred_guard_mutex);
[ 26.780481] lock(&p->lock);
[ 26.780481]
[ 26.780481] *** DEADLOCK ***
[ 26.780481]
[ 26.780481] 1 lock held by trinity-c5/848:
[ 26.780481] #0: (&sig->cred_guard_mutex){+.+.+.}, at: [<ffffffff811579db>] prepare_bprm_creds+0x2b/0x80
[ 26.780481]
[ 26.780481] stack backtrace:
[ 26.780481] CPU: 5 PID: 848 Comm: trinity-c5 Not tainted 3.13.0-11331-g6f008e72cd11 #1162
[ 26.780481] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS Bochs 01/01/2011
[ 26.780481] ffffffff824f1130 ffff8803b6973b58 ffffffff8172fc76 ffffffff824f1130
[ 26.780481] ffff8803b6973b98 ffffffff8172b6de ffff8803b6973bd0 ffff8803b72550e0
[ 26.780481] ffff8803b72550e0 0000000000000000 ffff8803b72549d0 0000000000000001
[ 26.780481] Call Trace:
[ 26.780481] [<ffffffff8172fc76>] dump_stack+0x4d/0x66
[ 26.780481] [<ffffffff8172b6de>] print_circular_bug+0x201/0x20f
[ 26.780481] [<ffffffff81097a4a>] validate_chain.isra.37+0x105a/0x10d0
[ 26.780481] [<ffffffff810998d8>] __lock_acquire+0x3a8/0xc20
[ 26.780481] [<ffffffff8109a1c6>] lock_acquire+0x76/0xc0
[ 26.780481] [<ffffffff811774a8>] ? seq_read+0x38/0x3c0
[ 26.780481] [<ffffffff81735bad>] mutex_lock_nested+0x6d/0x3d0
[ 26.780481] [<ffffffff811774a8>] ? seq_read+0x38/0x3c0
[ 26.780481] [<ffffffff811774a8>] ? seq_read+0x38/0x3c0
[ 26.780481] [<ffffffff81082e18>] ? sched_clock_cpu+0xa8/0xd0
[ 26.780481] [<ffffffff811774a8>] seq_read+0x38/0x3c0
[ 26.780481] [<ffffffff811b7af8>] proc_reg_read+0x38/0x70
[ 26.780481] [<ffffffff81167b9e>] ? dput+0x1e/0x110
[ 26.780481] [<ffffffff81150799>] vfs_read+0x99/0x160
[ 26.780481] [<ffffffff8115635c>] kernel_read+0x3c/0x50
[ 26.780481] [<ffffffff811565e7>] prepare_binprm+0x137/0x1d0
[ 26.780481] [<ffffffff81157f82>] do_execve_common.isra.34+0x4d2/0x730
[ 26.780481] [<ffffffff81157ba9>] ? do_execve_common.isra.34+0xf9/0x730
[ 26.780481] [<ffffffff8115c100>] ? mountpoint_last+0x1a0/0x1b0
[ 26.780481] [<ffffffff81158461>] SyS_execve+0x31/0x50
[ 26.780481] [<ffffffff81741099>] stub_execve+0x69/0xa0
It's easy triggable by trinity. Config is attached.
--
Kirill A. Shutemov
View attachment "config" of type "text/plain" (100094 bytes)
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