[PATCH v3] drm/amdgpu: annotate a false positive recursive locking
Chen, Guchun
Guchun.Chen at amd.com
Tue Aug 11 07:36:32 UTC 2020
[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.
Regards,
Guchun
-----Original Message-----
From: amd-gfx <amd-gfx-bounces at lists.freedesktop.org> On Behalf Of Christian König
Sent: Tuesday, August 11, 2020 2:53 PM
To: Li, Dennis <Dennis.Li at amd.com>; amd-gfx at lists.freedesktop.org; Deucher, Alexander <Alexander.Deucher at amd.com>; Kuehling, Felix <Felix.Kuehling at amd.com>; Zhang, Hawking <Hawking.Zhang at amd.com>; daniel at ffwll.ch
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 at amd.com>
>
> 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 at amd.com>
>
> 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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