On Tue, Aug 11, 2020 at 9:40 AM Christian König
<christian.koenig@xxxxxxx> wrote:
>
> Am 11.08.20 um 09:36 schrieb Chen, Guchun:
> > [AMD Public Use]
> >
> >> - down_write(&adev->reset_sem);
> >> + if (hive) {
> >> + down_write_nest_lock(&adev->reset_sem, &hive->hive_lock);
> >> + } else
> >> + down_write(&adev->reset_sem);
> > Coding style nit pick: You should drop the {} here.
> >
> > {} could not be dropped here, as down_write_nest_lock Is one macro with multiple lines, otherwise, build error would say 'else' missed one previous 'if'.
> > Instead of dropping, another {} should be added to else to include down_write(&adev->reset_sem), which makes the braces been balanced.
>
> Interesting bug, that is something which should not happen with macros
> in the Linux kernel. They protection by "do { ... } while(0)" is
> mandatory here.
Quick grep says it is protected like that ... can you pls paste the
full build error without {}?
-Daniel
>
> Let me take a look,
> Christian.
>
> >
> > Regards,
> > Guchun
> >
> > -----Original Message-----
> > From: amd-gfx <amd-gfx-bounces@xxxxxxxxxxxxxxxxxxxxx> On Behalf Of Christian König
> > Sent: Tuesday, August 11, 2020 2:53 PM
> > To: Li, Dennis <Dennis.Li@xxxxxxx>; amd-gfx@xxxxxxxxxxxxxxxxxxxxx; Deucher, Alexander <Alexander.Deucher@xxxxxxx>; Kuehling, Felix <Felix.Kuehling@xxxxxxx>; Zhang, Hawking <Hawking.Zhang@xxxxxxx>; daniel@xxxxxxxx
> > Subject: Re: [PATCH v3] drm/amdgpu: annotate a false positive recursive locking
> >
> > Am 11.08.20 um 04:12 schrieb Dennis Li:
> >> [ 584.110304] ============================================
> >> [ 584.110590] WARNING: possible recursive locking detected
> >> [ 584.110876] 5.6.0-deli-v5.6-2848-g3f3109b0e75f #1 Tainted: G OE
> >> [ 584.111164] --------------------------------------------
> >> [ 584.111456] kworker/38:1/553 is trying to acquire lock:
> >> [ 584.111721] ffff9b15ff0a47a0 (&adev->reset_sem){++++}, at:
> >> amdgpu_device_gpu_recover+0x262/0x1030 [amdgpu] [ 584.112112]
> >> but task is already holding lock:
> >> [ 584.112673] ffff9b1603d247a0 (&adev->reset_sem){++++}, at:
> >> amdgpu_device_gpu_recover+0x262/0x1030 [amdgpu] [ 584.113068]
> >> other info that might help us debug this:
> >> [ 584.113689] Possible unsafe locking scenario:
> >>
> >> [ 584.114350] CPU0
> >> [ 584.114685] ----
> >> [ 584.115014] lock(&adev->reset_sem);
> >> [ 584.115349] lock(&adev->reset_sem);
> >> [ 584.115678]
> >> *** DEADLOCK ***
> >>
> >> [ 584.116624] May be due to missing lock nesting notation
> >>
> >> [ 584.117284] 4 locks held by kworker/38:1/553:
> >> [ 584.117616] #0: ffff9ad635c1d348 ((wq_completion)events){+.+.},
> >> at: process_one_work+0x21f/0x630 [ 584.117967] #1: ffffac708e1c3e58
> >> ((work_completion)(&con->recovery_work)){+.+.}, at:
> >> process_one_work+0x21f/0x630 [ 584.118358] #2: ffffffffc1c2a5d0
> >> (&tmp->hive_lock){+.+.}, at: amdgpu_device_gpu_recover+0xae/0x1030 [amdgpu] [ 584.118786] #3: ffff9b1603d247a0 (&adev->reset_sem){++++}, at: amdgpu_device_gpu_recover+0x262/0x1030 [amdgpu] [ 584.119222]
> >> stack backtrace:
> >> [ 584.119990] CPU: 38 PID: 553 Comm: kworker/38:1 Kdump: loaded Tainted: G OE 5.6.0-deli-v5.6-2848-g3f3109b0e75f #1
> >> [ 584.120782] Hardware name: Supermicro SYS-7049GP-TRT/X11DPG-QT,
> >> BIOS 3.1 05/23/2019 [ 584.121223] Workqueue: events
> >> amdgpu_ras_do_recovery [amdgpu] [ 584.121638] Call Trace:
> >> [ 584.122050] dump_stack+0x98/0xd5
> >> [ 584.122499] __lock_acquire+0x1139/0x16e0 [ 584.122931] ?
> >> trace_hardirqs_on+0x3b/0xf0 [ 584.123358] ?
> >> cancel_delayed_work+0xa6/0xc0 [ 584.123771] lock_acquire+0xb8/0x1c0
> >> [ 584.124197] ? amdgpu_device_gpu_recover+0x262/0x1030 [amdgpu] [
> >> 584.124599] down_write+0x49/0x120 [ 584.125032] ?
> >> amdgpu_device_gpu_recover+0x262/0x1030 [amdgpu] [ 584.125472]
> >> amdgpu_device_gpu_recover+0x262/0x1030 [amdgpu] [ 584.125910] ?
> >> amdgpu_ras_error_query+0x1b8/0x2a0 [amdgpu] [ 584.126367]
> >> amdgpu_ras_do_recovery+0x159/0x190 [amdgpu] [ 584.126789]
> >> process_one_work+0x29e/0x630 [ 584.127208] worker_thread+0x3c/0x3f0
> >> [ 584.127621] ? __kthread_parkme+0x61/0x90 [ 584.128014]
> >> kthread+0x12f/0x150 [ 584.128402] ? process_one_work+0x630/0x630 [
> >> 584.128790] ? kthread_park+0x90/0x90 [ 584.129174]
> >> ret_from_fork+0x3a/0x50
> >>
> >> Each adev has owned lock_class_key to avoid false positive recursive
> >> locking.
> >>
> >> v2:
> >> 1. register adev->lock_key into lockdep, otherwise lockdep will report
> >> the below warning
> >>
> >> [ 1216.705820] BUG: key ffff890183b647d0 has not been registered!
> >> [ 1216.705924] ------------[ cut here ]------------ [ 1216.705972]
> >> DEBUG_LOCKS_WARN_ON(1) [ 1216.705997] WARNING: CPU: 20 PID: 541 at
> >> kernel/locking/lockdep.c:3743 lockdep_init_map+0x150/0x210
> >>
> >> v3:
> >> change to use down_write_nest_lock to annotate the false dead-lock
> >> warning.
> >>
> >> Signed-off-by: Dennis Li <Dennis.Li@xxxxxxx>
> >>
> >> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
> >> b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
> >> index 62ecac97fbd2..8a55b0bc044a 100644
> >> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
> >> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
> >> @@ -4145,12 +4145,15 @@ static int amdgpu_do_asic_reset(struct amdgpu_hive_info *hive,
> >> return r;
> >> }
> >>
> >> -static bool amdgpu_device_lock_adev(struct amdgpu_device *adev)
> >> +static bool amdgpu_device_lock_adev(struct amdgpu_device *adev,
> >> +struct amdgpu_hive_info *hive)
> >> {
> >> if (atomic_cmpxchg(&adev->in_gpu_reset, 0, 1) != 0)
> >> return false;
> >>
> >> - down_write(&adev->reset_sem);
> >> + if (hive) {
> >> + down_write_nest_lock(&adev->reset_sem, &hive->hive_lock);
> >> + } else
> >> + down_write(&adev->reset_sem);
> > Coding style nit pick: You should drop the {} here.
> >
> > Apart from that the patch is Reviewed-by: Christian König <christian.koenig@xxxxxxx>
> >
> >>
> >> atomic_inc(&adev->gpu_reset_counter);
> >> switch (amdgpu_asic_reset_method(adev)) { @@ -4312,7 +4315,7 @@ int
> >> amdgpu_device_gpu_recover(struct amdgpu_device *adev,
> >>
> >> /* block all schedulers and reset given job's ring */
> >> list_for_each_entry(tmp_adev, device_list_handle, gmc.xgmi.head) {
> >> - if (!amdgpu_device_lock_adev(tmp_adev)) {
> >> + if (!amdgpu_device_lock_adev(tmp_adev, hive)) {
> >> DRM_INFO("Bailing on TDR for s_job:%llx, as another already in progress",
> >> job ? job->base.id : -1);
> >> r = 0;
> > _______________________________________________
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> > amd-gfx@xxxxxxxxxxxxxxxxxxxxx
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>
--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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