From: Tejun Heo <tj@kernel.org>
To: Ming Lei <tom.leiming@gmail.com>
Cc: Christoph Lameter <cl@linux.com>,
Peter Zijlstra <a.p.zijlstra@chello.nl>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v1] percpu: use raw_local_irq_* in _this_cpu op
Date: Tue, 21 Feb 2012 09:30:42 -0800 [thread overview]
Message-ID: <20120221173042.GC12236@google.com> (raw)
In-Reply-To: <1329296078-17751-1-git-send-email-tom.leiming@gmail.com>
On Wed, Feb 15, 2012 at 04:54:38PM +0800, Ming Lei wrote:
> It doesn't make sense to trace irq off or do irq flags
> lock proving inside 'this_cpu' operations, so replace local_irq_*
> with raw_local_irq_* in 'this_cpu' op.
>
> Also the patch fixes onelockdep warning[1] by the replacement, see
> below:
>
> In commit: 933393f58fef9963eac61db8093689544e29a600(percpu:
> Remove irqsafe_cpu_xxx variants), local_irq_save/restore(flags) are
> added inside this_cpu_inc operation, so that trace_hardirqs_off_caller
> will be called by trace_hardirqs_on_caller directly because
> __debug_atomic_inc is implemented as this_cpu_inc, which may trigger
> the lockdep warning[1], for example in the below ARM scenary:
>
> kernel_thread_helper /*irq disabled*/
> ->trace_hardirqs_on_caller /*hardirqs_enabled was set*/
> ->trace_hardirqs_off_caller /*hardirqs_enabled cleared*/
> __this_cpu_add(redundant_hardirqs_on)
> ->trace_hardirqs_off_caller /*irq disabled, so call here*/
>
> The 'unannotated irqs-on' warning will be triggered somewhere because
> irq is just enabled after the irq trace in kernel_thread_helper.
>
> [1],
> [ 0.162841] ------------[ cut here ]------------
> [ 0.167694] WARNING: at kernel/lockdep.c:3493 check_flags+0xc0/0x1d0()
> [ 0.174468] Modules linked in:
> [ 0.177703] Backtrace:
> [ 0.180328] [<c00171f0>] (dump_backtrace+0x0/0x110) from [<c0412320>] (dump_stack+0x18/0x1c)
> [ 0.189086] r6:c051f778 r5:00000da5 r4:00000000 r3:60000093
> [ 0.195007] [<c0412308>] (dump_stack+0x0/0x1c) from [<c00410e8>] (warn_slowpath_common+0x54/0x6c)
> [ 0.204223] [<c0041094>] (warn_slowpath_common+0x0/0x6c) from [<c0041124>] (warn_slowpath_null+0x24/0x2c)
> [ 0.214111] r8:00000000 r7:00000000 r6:ee069598 r5:60000013 r4:ee082000
> [ 0.220825] r3:00000009
> [ 0.223693] [<c0041100>] (warn_slowpath_null+0x0/0x2c) from [<c0088f38>] (check_flags+0xc0/0x1d0)
> [ 0.232910] [<c0088e78>] (check_flags+0x0/0x1d0) from [<c008d348>] (lock_acquire+0x4c/0x11c)
> [ 0.241668] [<c008d2fc>] (lock_acquire+0x0/0x11c) from [<c0415aa4>] (_raw_spin_lock+0x3c/0x74)
> [ 0.250610] [<c0415a68>] (_raw_spin_lock+0x0/0x74) from [<c010a844>] (set_task_comm+0x20/0xc0)
> [ 0.259521] r6:ee069588 r5:ee0691c0 r4:ee082000
> [ 0.264404] [<c010a824>] (set_task_comm+0x0/0xc0) from [<c0060780>] (kthreadd+0x28/0x108)
> [ 0.272857] r8:00000000 r7:00000013 r6:c0044a08 r5:ee0691c0 r4:ee082000
> [ 0.279571] r3:ee083fe0
> [ 0.282470] [<c0060758>] (kthreadd+0x0/0x108) from [<c0044a08>] (do_exit+0x0/0x6dc)
> [ 0.290405] r5:c0060758 r4:00000000
> [ 0.294189] ---[ end trace 1b75b31a2719ed1c ]---
> [ 0.299041] possible reason: unannotated irqs-on.
> [ 0.303955] irq event stamp: 5
> [ 0.307159] hardirqs last enabled at (4): [<c001331c>] no_work_pending+0x8/0x2c
> [ 0.314880] hardirqs last disabled at (5): [<c0089b08>] trace_hardirqs_on_caller+0x60/0x26c
> [ 0.323547] softirqs last enabled at (0): [<c003f754>] copy_process+0x33c/0xef4
> [ 0.331207] softirqs last disabled at (0): [< (null)>] (null)
> [ 0.337585] CPU0: thread -1, cpu 0, socket 0, mpidr 80000000
>
> Acked-by: Christoph Lameter <cl@linux.com>
> Signed-off-by: Ming Lei <tom.leiming@gmail.com>
Applied to for-3.3-fixes. Thank you.
--
tejun
next prev parent reply other threads:[~2012-02-21 17:30 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-02-15 8:54 [PATCH v1] percpu: use raw_local_irq_* in _this_cpu op Ming Lei
2012-02-21 17:30 ` Tejun Heo [this message]
-- strict thread matches above, loose matches on Subject: below --
2012-02-15 4:36 Ming Lei
2012-02-15 4:59 ` Eric Dumazet
2012-02-15 5:08 ` Ming Lei
2012-02-15 6:03 ` Eric Dumazet
2012-02-15 8:56 ` Ming Lei
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