Being inside a spinlock signaling that the hardware just completed a
request doesn't prevent a second thread already spotting that the
request is complete, freeing it and reallocating it! The code currently
tries to prevent this using RCU -- but that only prevents the request
from being freed, it doesn't prevent us from reallocating it - that
requires us to take a reference.
[ 206.922985] BUG: spinlock already unlocked on CPU#4, gem_exec_parall/7796
[ 206.922994] lock: 0xffff8801c6047120, .magic: dead4ead, .owner: <none>/-1, .owner_cpu: -1
[ 206.923000] CPU: 4 PID: 7796 Comm: gem_exec_parall Not tainted 4.10.0-CI-Patchwork_4008+ #1
[ 206.923006] Hardware name: System manufacturer System Product Name/Z170M-PLUS, BIOS 1805 06/20/2016
[ 206.923012] Call Trace:
[ 206.923014] <IRQ>
[ 206.923019] dump_stack+0x67/0x92
[ 206.923023] spin_dump+0x73/0xc0
[ 206.923027] do_raw_spin_unlock+0x79/0xb0
[ 206.923031] _raw_spin_unlock_irqrestore+0x27/0x60
[ 206.923042] dma_fence_signal+0x160/0x230
[ 206.923060] notify_ring+0xae/0x2e0 [i915]
[ 206.923073] ? ibx_hpd_irq_handler+0xc0/0xc0 [i915]
[ 206.923086] gen8_gt_irq_handler+0x219/0x290 [i915]
[ 206.923100] gen8_irq_handler+0x8e/0x6b0 [i915]
[ 206.923105] __handle_irq_event_percpu+0x58/0x370
[ 206.923109] handle_irq_event_percpu+0x1e/0x50
[ 206.923113] handle_irq_event+0x34/0x60
[ 206.923117] handle_edge_irq+0xbe/0x150
[ 206.923122] handle_irq+0x15/0x20
[ 206.923126] do_IRQ+0x63/0x130
[ 206.923142] ? i915_mutex_lock_interruptible+0x39/0x140 [i915]
[ 206.923148] common_interrupt+0x90/0x90
[ 206.923153] RIP: 0010:osq_lock+0x77/0x110
[ 206.923157] RSP: 0018:ffffc90001cabaa0 EFLAGS: 00000246 ORIG_RAX: ffffffffffffff6e
[ 206.923164] RAX: 0000000000000000 RBX: ffff880236d1abc0 RCX: ffff8801ef642fc0
[ 206.923169] RDX: ffff8801ef6427c0 RSI: ffffffff81c6e7fd RDI: ffffffff81c7c848
[ 206.923175] RBP: ffffc90001cabab8 R08: 00000000692bb19b R09: 08c1493200000000
[ 206.923180] R10: 0000000000000001 R11: 0000000000000001 R12: ffff880236cdabc0
[ 206.923185] R13: ffff8802207f00b0 R14: ffffffffa00b7cd9 R15: ffff8802207f0070
[ 206.923191] </IRQ>
[ 206.923206] ? i915_mutex_lock_interruptible+0x39/0x140 [i915]
[ 206.923213] __mutex_lock+0x649/0x990
[ 206.923217] ? __mutex_lock+0xb0/0x990
[ 206.923221] ? _raw_spin_unlock+0x2c/0x50
[ 206.923226] ? __pm_runtime_resume+0x56/0x80
[ 206.923242] ? i915_mutex_lock_interruptible+0x39/0x140 [i915]
[ 206.923249] mutex_lock_interruptible_nested+0x16/0x20
[ 206.923264] i915_mutex_lock_interruptible+0x39/0x140 [i915]
[ 206.923270] ? __pm_runtime_resume+0x56/0x80
[ 206.923285] i915_gem_do_execbuffer.isra.15+0x442/0x1d10 [i915]
[ 206.923291] ? __lock_acquire+0x449/0x1b50
[ 206.923296] ? __might_fault+0x3e/0x90
[ 206.923301] ? __might_fault+0x87/0x90
[ 206.923305] ? __might_fault+0x3e/0x90
[ 206.923320] i915_gem_execbuffer2+0xb5/0x220 [i915]
[ 206.923327] drm_ioctl+0x200/0x450
[ 206.923341] ? i915_gem_execbuffer+0x330/0x330 [i915]
[ 206.923348] do_vfs_ioctl+0x90/0x6e0
[ 206.923352] ? __fget+0x108/0x200
[ 206.923356] ? expand_files+0x2b0/0x2b0
[ 206.923361] SyS_ioctl+0x3c/0x70
[ 206.923365] entry_SYSCALL_64_fastpath+0x1c/0xb1
[ 206.923369] RIP: 0033:0x7fdd75fc6357
[ 206.923373] RSP: 002b:00007fdd20e59bf8 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
[ 206.923380] RAX: ffffffffffffffda RBX: ffffffff81481ff3 RCX: 00007fdd75fc6357
[ 206.923385] RDX: 00007fdd20e59c70 RSI: 0000000040406469 RDI: 0000000000000003
[ 206.923390] RBP: ffffc90001cabf88 R08: 0000000000000040 R09: 00000000000003f7
[ 206.923396] R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
[ 206.923401] R13: 0000000000000003 R14: 0000000040406469 R15: 0000000001cf9cb0
[ 206.923408] ? __this_cpu_preempt_check+0x13/0x20
Fixes: 56299fb7d904 ("drm/i915: Signal first fence from irq handler if complete")
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=100051
Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Cc: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
Cc: Mika Kuoppala <mika.kuoppala@xxxxxxxxxxxxxxx>
---
drivers/gpu/drm/i915/i915_irq.c | 10 ++++------
1 file changed, 4 insertions(+), 6 deletions(-)
diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c
index 5fa2c4c56b09..73ab5abf20d7 100644
--- a/drivers/gpu/drm/i915/i915_irq.c
+++ b/drivers/gpu/drm/i915/i915_irq.c
@@ -1039,8 +1039,6 @@ static void notify_ring(struct intel_engine_cs *engine)
atomic_inc(&engine->irq_count);
set_bit(ENGINE_IRQ_BREADCRUMB, &engine->irq_posted);
- rcu_read_lock();
-
spin_lock(&engine->breadcrumbs.lock);
wait = engine->breadcrumbs.first_wait;
if (wait) {
@@ -1057,7 +1055,7 @@ static void notify_ring(struct intel_engine_cs *engine)
*/
if (i915_seqno_passed(intel_engine_get_seqno(engine),
wait->seqno))
- rq = wait->request;
+ rq = i915_gem_request_get(wait->request);
wake_up_process(wait->tsk);
} else {
@@ -1065,10 +1063,10 @@ static void notify_ring(struct intel_engine_cs *engine)
}
spin_unlock(&engine->breadcrumbs.lock);
- if (rq)
+ if (rq) {
dma_fence_signal(&rq->fence);
-
- rcu_read_unlock();
+ i915_gem_request_put(rq);
+ }
trace_intel_engine_notify(engine, wait);
}
--
2.11.0
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