Messages in this thread | | | Date | Tue, 21 Feb 2012 09:30:42 -0800 | From | Tejun Heo <> | Subject | Re: [PATCH v1] percpu: use raw_local_irq_* in _this_cpu op |
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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
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