Hi GG, On Tue, Mar 07, 2023 at 09:33:12AM +0200, Gwan-gyeong Mun wrote: > 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@xxxxxxxxx#dmesg-warnings1037 Thanks for looking into this. Yes, there is a basic locking issue here coming from migrate. migrate() takes the timeline lock and then calls the request_create() which tries to lock again. We inevitably fall into deadlock. The locking of the timeline is quite exotic, it's started in request_create() and released in request_add(). It's still in trybot, but this is supposed to be the next version: https://patchwork.freedesktop.org/series/114645/ This creates new version of request_create_locked() and request_add_locked() where there the timeline is not locked in the process. There are still some selftests that need to be fixed, though. Andi > <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(-) > >
