[Intel-gfx] [PATCH v3 0/2] Fix error propagation amongst request

Tue Mar 7 07:33:12 UTC 2023

Hi Andi,

After applying these two patches, deadlock is being detected in the call 
stack below. Please review whether the patch to update the 
intel_context_migrate_copy() part affected the deadlock.

https://intel-gfx-ci.01.org/tree/drm-tip/Patchwork_114451v1/bat-dg2-8/igt@i915_module_load@load.html#dmesg-warnings1037

<4> [33.070967] ============================================
<4> [33.070968] WARNING: possible recursive locking detected
<4> [33.070969] 6.2.0-Patchwork_114451v1-g8589fd9227ca+ #1 Not tainted
<4> [33.070970] --------------------------------------------
<4> [33.070971] i915_module_loa/948 is trying to acquire lock:
<4> [33.070972] ffff8881127f0478 (migrate){+.+.}-{3:3}, at: 
i915_request_create+0x1c6/0x230 [i915]
<4> [33.071215]
but task is already holding lock:
<4> [33.071235] ffff8881127f0478 (migrate){+.+.}-{3:3}, at: 
intel_context_migrate_copy+0x1b3/0xa80 [i915]
<4> [33.071484]
other info that might help us debug this:
<4> [33.071504]  Possible unsafe locking scenario:
<4> [33.071522]        CPU0
<4> [33.071532]        ----
<4> [33.071541]   lock(migrate);
<4> [33.071554]   lock(migrate);
<4> [33.071567]
  *** DEADLOCK ***
<4> [33.071585]  May be due to missing lock nesting notation
<4> [33.071606] 3 locks held by i915_module_loa/948:
<4> [33.071622]  #0: ffffc90001eb7b70 
(reservation_ww_class_acquire){+.+.}-{0:0}, at: 
i915_gem_do_execbuffer+0xae2/0x21c0 [i915]
<4> [33.071893]  #1: ffff8881127b9c28 
(reservation_ww_class_mutex){+.+.}-{3:3}, at: 
__intel_context_do_pin_ww+0x7a/0xa30 [i915]
<4> [33.072133]  #2: ffff8881127f0478 (migrate){+.+.}-{3:3}, at: 
intel_context_migrate_copy+0x1b3/0xa80 [i915]
<4> [33.072384]
stack backtrace:
<4> [33.072399] CPU: 7 PID: 948 Comm: i915_module_loa Not tainted 
6.2.0-Patchwork_114451v1-g8589fd9227ca+ #1
<4> [33.072428] Hardware name: Intel Corporation CoffeeLake Client 
Platform/CoffeeLake S UDIMM RVP, BIOS CNLSFWR1.R00.X220.B00.2103302221 
03/30/2021
<4> [33.072465] Call Trace:
<4> [33.072475]  <TASK>
<4> [33.072486]  dump_stack_lvl+0x5b/0x85
<4> [33.072503]  __lock_acquire.cold+0x158/0x33b
<4> [33.072524]  lock_acquire+0xd6/0x310
<4> [33.072541]  ? i915_request_create+0x1c6/0x230 [i915]
<4> [33.072812]  __mutex_lock+0x95/0xf40
<4> [33.072829]  ? i915_request_create+0x1c6/0x230 [i915]
<4> [33.073093]  ? rcu_read_lock_sched_held+0x55/0x80
<4> [33.073112]  ? __mutex_lock+0x133/0xf40
<4> [33.073128]  ? i915_request_create+0x1c6/0x230 [i915]
<4> [33.073388]  ? intel_context_migrate_copy+0x1b3/0xa80 [i915]
<4> [33.073619]  ? i915_request_create+0x1c6/0x230 [i915]
<4> [33.073876]  i915_request_create+0x1c6/0x230 [i915]
<4> [33.074135]  intel_context_migrate_copy+0x1d0/0xa80 [i915]
<4> [33.074360]  __i915_ttm_move+0x7a8/0x940 [i915]
<4> [33.074538]  ? _raw_spin_unlock_irqrestore+0x41/0x70
<4> [33.074552]  ? dma_resv_iter_next+0x91/0xb0
<4> [33.074564]  ? dma_resv_iter_first+0x42/0xb0
<4> [33.074576]  ? i915_deps_add_resv+0x4c/0xc0 [i915]
<4> [33.074744]  i915_ttm_move+0x2ac/0x430 [i915]
<4> [33.074910]  ttm_bo_handle_move_mem+0xb5/0x140 [ttm]
<4> [33.074930]  ttm_bo_validate+0xe9/0x1a0 [ttm]
<4> [33.074947]  __i915_ttm_get_pages+0x4e/0x190 [i915]
<4> [33.075112]  i915_ttm_get_pages+0xf3/0x160 [i915]
<4> [33.075280]  ____i915_gem_object_get_pages+0x36/0xb0 [i915]
<4> [33.075446]  __i915_gem_object_get_pages+0x95/0xa0 [i915]
<4> [33.075608]  i915_vma_get_pages+0xfa/0x160 [i915]
<4> [33.075779]  i915_vma_pin_ww+0xdc/0xb50 [i915]
<4> [33.075953]  eb_validate_vmas+0x1c6/0xac0 [i915]
<4> [33.076114]  i915_gem_do_execbuffer+0xb2a/0x21c0 [i915]
<4> [33.076276]  ? __stack_depot_save+0x3f/0x4e0
<4> [33.076292]  ? 0xffffffff81000000
<4> [33.076301]  ? _raw_spin_unlock_irq+0x41/0x50
<4> [33.076312]  ? lockdep_hardirqs_on+0xc3/0x140
<4> [33.076325]  ? set_track_update+0x25/0x50
<4> [33.076338]  ? __lock_acquire+0x5f2/0x2130
<4> [33.076356]  i915_gem_execbuffer2_ioctl+0x123/0x2e0 [i915]
<4> [33.076519]  ? __pfx_i915_gem_execbuffer2_ioctl+0x10/0x10 [i915]
<4> [33.076679]  drm_ioctl_kernel+0xb4/0x150
<4> [33.076692]  drm_ioctl+0x21d/0x420
<4> [33.076703]  ? __pfx_i915_gem_execbuffer2_ioctl+0x10/0x10 [i915]
<4> [33.076864]  ? __vm_munmap+0xd3/0x170
<4> [33.076877]  __x64_sys_ioctl+0x76/0xb0
<4> [33.076889]  do_syscall_64+0x3c/0x90
<4> [33.076900]  entry_SYSCALL_64_after_hwframe+0x72/0xdc
<4> [33.076913] RIP: 0033:0x7f304aa903ab
<4> [33.076923] Code: 0f 1e fa 48 8b 05 e5 7a 0d 00 64 c7 00 26 00 00 00 
48 c7 c0 ff ff ff ff c3 66 0f 1f 44 00 00 f3 0f 1e fa b8 10 00 00 00 0f 
05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d b5 7a 0d 00 f7 d8 64 89 01 48
<4> [33.076957] RSP: 002b:00007fffb1424cf8 EFLAGS: 00000246 ORIG_RAX: 
0000000000000010
<4> [33.076975] RAX: ffffffffffffffda RBX: 00007fffb1424da0 RCX: 
00007f304aa903ab
<4> [33.076990] RDX: 00007fffb1424da0 RSI: 0000000040406469 RDI: 
0000000000000005
<4> [33.077004] RBP: 0000000040406469 R08: 0000000000000005 R09: 
0000000100003000
<4> [33.077019] R10: 0000000000000001 R11: 0000000000000246 R12: 
0000000000010000
<4> [33.077034] R13: 0000000000000005 R14: 00000000ffffffff R15: 
00000000000056a0
<4> [33.077052]  </TASK>

Br,

G.G.

On 2/28/23 4:11 AM, Andi Shyti wrote:
> Hi,
> 
> This series of two patches fixes the issue introduced in
> cf586021642d80 ("drm/i915/gt: Pipelined page migration") where,
> as reported by Matt, in a chain of requests an error is reported
> only if happens in the last request.
> 
> However Chris noticed that without ensuring exclusivity in the
> locking we might end up in some deadlock. That's why patch 1
> throttles for the ringspace in order to make sure that no one is
> holding it.
> 
> Version 1 of this patch has been reviewed by matt and this
> version is adding Chris exclusive locking.
> 
> Thanks Chris for this work.
> 
> Andi
> 
> Changelog
> =========
> v1 -> v2
>   - Add patch 1 for ensuring exclusive locking of the timeline
>   - Reword git commit of patch 2.
> 
> Andi Shyti (1):
>    drm/i915/gt: Make sure that errors are propagated through request
>      chains
> 
> Chris Wilson (1):
>    drm/i915: Throttle for ringspace prior to taking the timeline mutex
> 
>   drivers/gpu/drm/i915/gt/intel_context.c | 41 +++++++++++++++++++++++++
>   drivers/gpu/drm/i915/gt/intel_context.h |  2 ++
>   drivers/gpu/drm/i915/gt/intel_migrate.c | 39 +++++++++++++++++------
>   drivers/gpu/drm/i915/i915_request.c     |  3 ++
>   4 files changed, 75 insertions(+), 10 deletions(-)
> 