We have to avoid taking ww_mutex inside the shrinker as we use it as a
plain mutex type and so need to avoid recursive deadlocks:
[ 602.771969] =================================
[ 602.771970] [ INFO: inconsistent lock state ]
[ 602.771973] 4.10.0gpudebug+ #122 Not tainted
[ 602.771974] ---------------------------------
[ 602.771975] inconsistent {RECLAIM_FS-ON-W} -> {IN-RECLAIM_FS-W} usage.
[ 602.771978] kswapd0/40 [HC0[0]:SC0[0]:HE1:SE1] takes:
[ 602.771979] (reservation_ww_class_mutex){+.+.?.}, at: [<ffffffffa054680a>] i915_gem_object_wait+0x39a/0x410 [i915]
[ 602.772020] {RECLAIM_FS-ON-W} state was registered at:
[ 602.772024] mark_held_locks+0x76/0x90
[ 602.772026] lockdep_trace_alloc+0xb8/0xc0
[ 602.772028] __kmalloc_track_caller+0x5d/0x130
[ 602.772031] krealloc+0x89/0xb0
[ 602.772033] reservation_object_reserve_shared+0xaf/0xd0
[ 602.772055] i915_gem_do_execbuffer.isra.35+0x1413/0x18b0 [i915]
[ 602.772075] i915_gem_execbuffer2+0x10e/0x1d0 [i915]
[ 602.772078] drm_ioctl+0x291/0x480
[ 602.772079] do_vfs_ioctl+0x695/0x6f0
[ 602.772081] SyS_ioctl+0x3c/0x70
[ 602.772084] entry_SYSCALL_64_fastpath+0x18/0xad
[ 602.772085] irq event stamp: 5197423
[ 602.772088] hardirqs last enabled at (5197423): [<ffffffff8116751d>] kfree+0xdd/0x170
[ 602.772091] hardirqs last disabled at (5197422): [<ffffffff811674f9>] kfree+0xb9/0x170
[ 602.772095] softirqs last enabled at (5190992): [<ffffffff8107bfe1>] __do_softirq+0x221/0x280
[ 602.772097] softirqs last disabled at (5190575): [<ffffffff8107c294>] irq_exit+0x64/0xc0
[ 602.772099]
other info that might help us debug this:
[ 602.772100] Possible unsafe locking scenario:
[ 602.772101] CPU0
[ 602.772101] ----
[ 602.772102] lock(reservation_ww_class_mutex);
[ 602.772104] <Interrupt>
[ 602.772105] lock(reservation_ww_class_mutex);
[ 602.772107]
*** DEADLOCK ***
[ 602.772109] 2 locks held by kswapd0/40:
[ 602.772110] #0: (shrinker_rwsem){++++..}, at: [<ffffffff811337b5>] shrink_slab.constprop.62+0x35/0x280
[ 602.772116] #1: (&dev->struct_mutex){+.+.+.}, at: [<ffffffffa0553957>] i915_gem_shrinker_lock+0x27/0x60 [i915]
[ 602.772141]
stack backtrace:
[ 602.772144] CPU: 2 PID: 40 Comm: kswapd0 Not tainted 4.10.0gpudebug+ #122
[ 602.772145] Hardware name: LENOVO 42433ZG/42433ZG, BIOS 8AET64WW (1.44 ) 07/26/2013
[ 602.772147] Call Trace:
[ 602.772151] dump_stack+0x68/0xa1
[ 602.772153] print_usage_bug+0x1d4/0x1f0
[ 602.772155] mark_lock+0x390/0x530
[ 602.772157] ? print_irq_inversion_bug+0x200/0x200
[ 602.772159] __lock_acquire+0x405/0x1260
[ 602.772181] ? i915_gem_object_wait+0x39a/0x410 [i915]
[ 602.772183] lock_acquire+0x60/0x80
[ 602.772205] ? i915_gem_object_wait+0x39a/0x410 [i915]
[ 602.772207] mutex_lock_nested+0x69/0x760
[ 602.772229] ? i915_gem_object_wait+0x39a/0x410 [i915]
[ 602.772231] ? kfree+0xdd/0x170
[ 602.772253] ? i915_gem_object_wait+0x163/0x410 [i915]
[ 602.772255] ? trace_hardirqs_on_caller+0x18d/0x1c0
[ 602.772256] ? trace_hardirqs_on+0xd/0x10
[ 602.772278] i915_gem_object_wait+0x39a/0x410 [i915]
[ 602.772300] i915_gem_object_unbind+0x5e/0x130 [i915]
[ 602.772323] i915_gem_shrink+0x22d/0x3d0 [i915]
[ 602.772347] i915_gem_shrinker_scan+0x3f/0x80 [i915]
[ 602.772349] shrink_slab.constprop.62+0x1ad/0x280
[ 602.772352] shrink_node+0x52/0x80
[ 602.772355] kswapd+0x427/0x5c0
[ 602.772358] kthread+0x122/0x130
[ 602.772360] ? try_to_free_pages+0x270/0x270
[ 602.772362] ? kthread_stop+0x70/0x70
[ 602.772365] ret_from_fork+0x2e/0x40
v2: Add commentary about the pruning being opportunistic
Reported-by: Jan Nordholz <jckn@xxxxxxx>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=99977#c10
Fixes: e54ca9774777 ("drm/i915: Remove completed fences after a wait")
Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Cc: Joonas Lahtinen <joonas.lahtinen@xxxxxxxxxxxxxxx>
Cc: Matthew Auld <matthew.auld@xxxxxxxxx>
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@xxxxxxxxxxxxxxx>
---
drivers/gpu/drm/i915/i915_gem.c | 13 +++++++++----
1 file changed, 9 insertions(+), 4 deletions(-)
diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index e29f9400c9d1..aca1eaddafb4 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -462,11 +462,16 @@ i915_gem_object_wait_reservation(struct reservation_object *resv,
dma_fence_put(excl);
+ /* Oportunistically prune the fences iff we know they have *all* been
+ * signaled and that the reservation object has not been changed (i.e.
+ * no new fences have been added).
+ */
if (prune_fences && !__read_seqcount_retry(&resv->seq, seq)) {
- reservation_object_lock(resv, NULL);
- if (!__read_seqcount_retry(&resv->seq, seq))
- reservation_object_add_excl_fence(resv, NULL);
- reservation_object_unlock(resv);
+ if (reservation_object_trylock(resv)) {
+ if (!__read_seqcount_retry(&resv->seq, seq))
+ reservation_object_add_excl_fence(resv, NULL);
+ reservation_object_unlock(resv);
+ }
}
return timeout;
--
2.11.0
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