As __active_retire() does it's final atomic_dec() under the ref->tree_lock spinlock, in order to prevent ourselves from reusing the ref->cache and ref->tree as they are being destroyed, we need to serialise with the retirement during i915_active_acquire().
[ +0.000005] kernel BUG at drivers/gpu/drm/i915/i915_active.c:157! [ +0.000011] invalid opcode: 0000 [#1] SMP [ +0.000004] CPU: 7 PID: 188 Comm: kworker/u16:4 Not tainted 5.4.0-rc8-03070-gac5e57322614 #89 [ +0.000002] Hardware name: Razer Razer Blade Stealth 13 Late 2019/LY320, BIOS 1.02 09/10/2019 [ +0.000082] Workqueue: events_unbound active_work [i915] [ +0.000059] RIP: 0010:__active_retire+0x115/0x120 [i915] [ +0.000003] Code: 75 28 48 8b 3d 8c 6e 1a 00 48 89 ee e8 e4 5f a5 c0 48 8b 44 24 10 65 48 33 04 25 28 00 00 00 75 0f 48 83 c4 18 5b 5d 41 5c c3 <0f> 0b 0f 0b 0f 0b e8 a0 90 87 c0 0f 1f 44 00 00 48 8b 3d 54 6e 1a [ +0.000002] RSP: 0018:ffffb833003f7e48 EFLAGS: 00010286 [ +0.000003] RAX: ffff8d6e8d726d00 RBX: ffff8d6f9db4e840 RCX: 0000000000000000 [ +0.000001] RDX: ffffffff82605930 RSI: ffff8d6f9adc4908 RDI: ffff8d6e96cefe28 [ +0.000002] RBP: ffff8d6e96cefe00 R08: 0000000000000000 R09: ffff8d6f9ffe9a50 [ +0.000002] R10: 0000000000000048 R11: 0000000000000018 R12: ffff8d6f9adc4930 [ +0.000001] R13: ffff8d6f9e04fb00 R14: 0000000000000000 R15: ffff8d6f9adc4988 [ +0.000002] FS: 0000000000000000(0000) GS:ffff8d6f9ffc0000(0000) knlGS:0000000000000000 [ +0.000002] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ +0.000002] CR2: 000055eb5a34cf10 CR3: 000000018d609002 CR4: 0000000000760ee0 [ +0.000002] PKRU: 55555554 [ +0.000001] Call Trace: [ +0.000010] process_one_work+0x1aa/0x350 [ +0.000004] worker_thread+0x4d/0x3a0 [ +0.000004] kthread+0xfb/0x130 [ +0.000004] ? process_one_work+0x350/0x350 [ +0.000003] ? kthread_park+0x90/0x90 [ +0.000005] ret_from_fork+0x1f/0x40
Reported-by: Kenneth Graunke kenneth@whitecape.org Fixes: c9ad602feabe ("drm/i915: Split i915_active.mutex into an irq-safe spinlock for the rbtree") Signed-off-by: Chris Wilson chris@chris-wilson.co.uk Cc: Tvrtko Ursulin tvrtko.ursulin@intel.com Cc: Kenneth Graunke kenneth@whitecape.org Cc: Matthew Auld matthew.auld@intel.com Tested-by: Kenneth Graunke kenneth@whitecape.org Reviewed-by: Kenneth Graunke kenneth@whitecape.org Link: https://patchwork.freedesktop.org/patch/msgid/20191205183332.801237-1-chris@... (cherry picked from commit bbca083de291a03ffe1a1eb0832a0d74f8b64898) --- drivers/gpu/drm/i915/i915_active.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/drivers/gpu/drm/i915/i915_active.c b/drivers/gpu/drm/i915/i915_active.c index a19e7d89bc8a..378b52d1ab74 100644 --- a/drivers/gpu/drm/i915/i915_active.c +++ b/drivers/gpu/drm/i915/i915_active.c @@ -91,10 +91,9 @@ static void debug_active_init(struct i915_active *ref)
static void debug_active_activate(struct i915_active *ref) { - spin_lock_irq(&ref->tree_lock); + lockdep_assert_held(&ref->tree_lock); if (!atomic_read(&ref->count)) /* before the first inc */ debug_object_activate(ref, &active_debug_desc); - spin_unlock_irq(&ref->tree_lock); }
static void debug_active_deactivate(struct i915_active *ref) @@ -407,8 +406,10 @@ int i915_active_acquire(struct i915_active *ref) if (!atomic_read(&ref->count) && ref->active) err = ref->active(ref); if (!err) { + spin_lock_irq(&ref->tree_lock); /* vs __active_retire() */ debug_active_activate(ref); atomic_inc(&ref->count); + spin_unlock_irq(&ref->tree_lock); }
mutex_unlock(&ref->mutex);