dma_buf_detach lockdep splat
Thomas Hellström
thomas.hellstrom at linux.intel.com
Wed Jun 26 15:58:02 UTC 2024
Hi!
I'm seeing the below lockdep splat 1) with the xe driver in an imported
dma-buf object destruction path.
It's not because we hold the dma_resv lock at that point, but rather
because we hold *another* dma_resv lock at that point, and the dma_resv
detach happens when the object is idle, in this case it was idle at the
final put(), and dma_buf_detach() is called in the putting process.
Holding another dma-buf lock might happen as part of
drm_exec_unlock_all, or simply if the wider vm dma_resv was held at
object put time, so it's not an uncommon pattern, even if the drm_exec
instance can be fixed by putting all bos after unlocking them all.
Two solutions coming to mind here:
1) Provide a dma_buf_detach_locked()
2) Have TTM always take the delayed delete path for imported dma-buf
objects.
I'd prefer 1) since I think the correct place to call this is in the
TTM callback delete_mem_notify() where the bo is already locked, and I
figure non-TTM gem backends may come to suffer from the same problem.
Opinions, suggestions?
[1]
[ 99.136161] ============================================
[ 99.136162] WARNING: possible recursive locking detected
[ 99.136163] 6.10.0-rc2+ #6 Tainted: G U
[ 99.136165] --------------------------------------------
[ 99.136166] glxgears:sh0/4675 is trying to acquire lock:
[ 99.136167] ffff9967dcdd91a8 (reservation_ww_class_mutex){+.+.}-
{3:3}, at: dma_buf_detach+0x3b/0xf0
[ 99.136184]
but task is already holding lock:
[ 99.136186] ffff9967d8c145a8 (reservation_ww_class_mutex){+.+.}-
{3:3}, at: drm_exec_lock_obj+0x49/0x2b0 [drm_exec]
[ 99.136191]
other info that might help us debug this:
[ 99.136192] Possible unsafe locking scenario:
[ 99.136194] CPU0
[ 99.136194] ----
[ 99.136195] lock(reservation_ww_class_mutex);
[ 99.136197] lock(reservation_ww_class_mutex);
[ 99.136199]
*** DEADLOCK ***
[ 99.136199] May be due to missing lock nesting notation
[ 99.136200] 5 locks held by glxgears:sh0/4675:
[ 99.136202] #0: ffff9967d8c104c8 (&xef->vm.lock){+.+.}-{3:3}, at:
xe_file_close+0xde/0x1c0 [xe]
[ 99.136272] #1: ffff9967d5bb7480 (&vm->lock){++++}-{3:3}, at:
xe_vm_close_and_put+0x161/0x9b0 [xe]
[ 99.136350] #2: ffff9967ef88a970 (&val->lock){.+.+}-{3:3}, at:
xe_validation_ctx_init+0x6d/0x70 [xe]
[ 99.136440] #3: ffffbd6a085577b8
(reservation_ww_class_acquire){+.+.}-{0:0}, at:
xe_vma_destroy_unlocked+0x7f/0xe0 [xe]
[ 99.136546] #4: ffff9967d8c145a8
(reservation_ww_class_mutex){+.+.}-{3:3}, at:
drm_exec_lock_obj+0x49/0x2b0 [drm_exec]
[ 99.136552]
stack backtrace:
[ 99.136553] CPU: 10 PID: 4675 Comm: glxgears:sh0 Tainted: G U
6.10.0-rc2+ #6
[ 99.136555] Hardware name: ASUS System Product Name/PRIME B560M-A
AC, BIOS 2001 02/01/2023
[ 99.136557] Call Trace:
[ 99.136558] <TASK>
[ 99.136560] dump_stack_lvl+0x77/0xb0
[ 99.136564] __lock_acquire+0x1232/0x2160
[ 99.136569] lock_acquire+0xcb/0x2d0
[ 99.136570] ? dma_buf_detach+0x3b/0xf0
[ 99.136574] ? __lock_acquire+0x417/0x2160
[ 99.136577] __ww_mutex_lock.constprop.0+0xd0/0x13b0
[ 99.136580] ? dma_buf_detach+0x3b/0xf0
[ 99.136584] ? dma_buf_detach+0x3b/0xf0
[ 99.136588] ? ww_mutex_lock+0x2b/0x90
[ 99.136590] ww_mutex_lock+0x2b/0x90
[ 99.136592] dma_buf_detach+0x3b/0xf0
[ 99.136595] drm_prime_gem_destroy+0x2f/0x40 [drm]
[ 99.136638] xe_ttm_bo_destroy+0x32/0x220 [xe]
[ 99.136734] ? __mutex_unlock_slowpath+0x3a/0x290
[ 99.136738] drm_exec_unlock_all+0xa1/0xd0 [drm_exec]
[ 99.136741] drm_exec_fini+0x12/0xb0 [drm_exec]
[ 99.136743] xe_validation_ctx_fini+0x15/0x40 [xe]
[ 99.136848] xe_vma_destroy_unlocked+0xb1/0xe0 [xe]
[ 99.136954] xe_vm_close_and_put+0x41a/0x9b0 [xe]
[ 99.137056] ? xa_find+0xe3/0x1e0
[ 99.137060] xe_file_close+0x10a/0x1c0 [xe]
[ 99.137157] drm_file_free+0x22a/0x280 [drm]
[ 99.137193] drm_release_noglobal+0x22/0x70 [drm]
[ 99.137227] __fput+0xf1/0x2d0
[ 99.137231] task_work_run+0x59/0x90
[ 99.137235] do_exit+0x330/0xb40
[ 99.137238] do_group_exit+0x36/0xa0
[ 99.137241] get_signal+0xbd2/0xbe0
[ 99.137245] arch_do_signal_or_restart+0x3e/0x240
[ 99.137249] syscall_exit_to_user_mode+0x1e7/0x290
[ 99.137252] do_syscall_64+0xa1/0x180
[ 99.137255] ? _raw_spin_unlock+0x23/0x40
[ 99.137257] ? look_up_lock_class+0x6f/0x120
[ 99.137261] ? __lock_acquire+0x417/0x2160
[ 99.137264] ? lock_acquire+0xcb/0x2d0
[ 99.137266] ? __set_task_comm+0x28/0x1e0
[ 99.137268] ? find_held_lock+0x2b/0x80
[ 99.137271] ? __set_task_comm+0xe1/0x1e0
[ 99.137273] ? lock_release+0xca/0x290
[ 99.137277] ? __do_sys_prctl+0x245/0xab0
[ 99.137279] ? lockdep_hardirqs_on_prepare+0xde/0x190
[ 99.137281] ? syscall_exit_to_user_mode+0xb0/0x290
[ 99.137284] ? do_syscall_64+0xa1/0x180
[ 99.137286] ? cpuset_cpus_allowed+0x36/0x140
[ 99.137289] ? find_held_lock+0x2b/0x80
[ 99.137291] ? find_held_lock+0x2b/0x80
[ 99.137294] ? __sched_setaffinity+0x78/0x240
[ 99.137297] ? kfree+0xe2/0x310
[ 99.137301] ? kfree+0x202/0x310
[ 99.137303] ? __sched_setaffinity+0x78/0x240
[ 99.137305] ? __x64_sys_sched_setaffinity+0x69/0xb0
[ 99.137307] ? kfree+0xe2/0x310
[ 99.137310] ? lockdep_hardirqs_on_prepare+0xde/0x190
[ 99.137312] ? syscall_exit_to_user_mode+0xb0/0x290
[ 99.137315] ? do_syscall_64+0xa1/0x180
[ 99.137317] ? trace_hardirqs_off+0x4b/0xc0
[ 99.137321] ? clear_bhb_loop+0x45/0xa0
[ 99.137325] ? clear_bhb_loop+0x45/0xa0
[ 99.137327] ? clear_bhb_loop+0x45/0xa0
[ 99.137330] entry_SYSCALL_64_after_hwframe+0x76/0x7e
[ 99.137333] RIP: 0033:0x7fda70ee6169
[ 99.137351] Code: Unable to access opcode bytes at 0x7fda70ee613f.
[ 99.137352] RSP: 002b:00007fda5fdffc80 EFLAGS: 00000246 ORIG_RAX:
00000000000000ca
[ 99.137354] RAX: fffffffffffffe00 RBX: 0000000000000000 RCX:
00007fda70ee6169
[ 99.137356] RDX: 0000000000000000 RSI: 0000000000000189 RDI:
0000564a96f45b30
[ 99.137358] RBP: 00007fda5fdffcb0 R08: 0000000000000000 R09:
00000000ffffffff
[ 99.137359] R10: 0000000000000000 R11: 0000000000000246 R12:
0000000000000000
[ 99.137360] R13: 0000000000000000 R14: 0000000000000000 R15:
0000564a96f45b30
[ 99.137365] </TASK>
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