| Message ID | 20200206204915.2636606-2-chris@chris-wilson.co.uk (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [1/4] drm/i915/gt: Prevent queuing retire workers on the virtual engine | expand |
Chris Wilson <chris@chris-wilson.co.uk> writes: > Mika spotted > > <4>[17436.705441] general protection fault: 0000 [#1] PREEMPT SMP PTI > <4>[17436.705447] CPU: 2 PID: 0 Comm: swapper/2 Not tainted 5.5.0+ #1 > <4>[17436.705449] Hardware name: System manufacturer System Product Name/Z170M-PLUS, BIOS 3805 05/16/2018 > <4>[17436.705512] RIP: 0010:__execlists_submission_tasklet+0xc4d/0x16e0 [i915] > <4>[17436.705516] Code: c5 4c 8d 60 e0 75 17 e9 8c 07 00 00 49 8b 44 24 20 49 39 c5 4c 8d 60 e0 0f 84 7a 07 00 00 49 8b 5c 24 08 49 8b 87 80 00 00 00 <48> 39 83 d8 fe ff ff 75 d9 48 8b 83 88 fe ff ff a8 01 0f 84 b6 05 > <4>[17436.705518] RSP: 0018:ffffc9000012ce80 EFLAGS: 00010083 > <4>[17436.705521] RAX: ffff88822ae42000 RBX: 5a5a5a5a5a5a5a5a RCX: dead000000000122 > <4>[17436.705523] RDX: ffff88822ae42588 RSI: ffff8881e32a7908 RDI: ffff8881c429fd48 > <4>[17436.705525] RBP: ffffc9000012cf00 R08: ffff88822ae42588 R09: 00000000fffffffe > <4>[17436.705527] R10: ffff8881c429fb80 R11: 00000000a677cf08 R12: ffff8881c42a0aa8 > <4>[17436.705529] R13: ffff8881c429fd38 R14: ffff88822ae42588 R15: ffff8881c429fb80 > <4>[17436.705532] FS: 0000000000000000(0000) GS:ffff88822ed00000(0000) knlGS:0000000000000000 > <4>[17436.705534] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > <4>[17436.705536] CR2: 00007f858c76d000 CR3: 0000000005610003 CR4: 00000000003606e0 > <4>[17436.705538] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 > <4>[17436.705540] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 > <4>[17436.705542] Call Trace: > <4>[17436.705545] <IRQ> > <4>[17436.705603] execlists_submission_tasklet+0xc0/0x130 [i915] > > which is us consuming a partially initialised new waiter in > defer_requests(). We can prevent this by initialising the i915_dependency > prior to making it visible, and since we are using a concurrent > list_add/iterator mark them up to the compiler. I tried to find the culprit myself but was confused if it was the request or the waiter which was wrong. So here is a short summary of discussion in irc: RBX: 5a5a5a...is POISON_INUSE Requests won't get poisoned as they are reused and protected by rcu. Thus it points to waiter and the evidence and code matches so, Reviewed-by: Mika Kuoppala <mika.kuoppala@linux.intel.com> > > Fixes: 8ee36e048c98 ("drm/i915/execlists: Minimalistic timeslicing") > Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk> > Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com> > --- > drivers/gpu/drm/i915/gt/intel_lrc.c | 7 ++++++- > drivers/gpu/drm/i915/i915_scheduler.c | 5 +++-- > 2 files changed, 9 insertions(+), 3 deletions(-) > > diff --git a/drivers/gpu/drm/i915/gt/intel_lrc.c b/drivers/gpu/drm/i915/gt/intel_lrc.c > index c196fb90c59f..b350e01d86d2 100644 > --- a/drivers/gpu/drm/i915/gt/intel_lrc.c > +++ b/drivers/gpu/drm/i915/gt/intel_lrc.c > @@ -1615,6 +1615,11 @@ last_active(const struct intel_engine_execlists *execlists) > return *last; > } > > +#define for_each_waiter(p__, rq__) \ > + list_for_each_entry_lockless(p__, \ > + &(rq__)->sched.waiters_list, \ > + wait_link) > + > static void defer_request(struct i915_request *rq, struct list_head * const pl) > { > LIST_HEAD(list); > @@ -1632,7 +1637,7 @@ static void defer_request(struct i915_request *rq, struct list_head * const pl) > GEM_BUG_ON(i915_request_is_active(rq)); > list_move_tail(&rq->sched.link, pl); > > - list_for_each_entry(p, &rq->sched.waiters_list, wait_link) { > + for_each_waiter(p, rq) { > struct i915_request *w = > container_of(p->waiter, typeof(*w), sched); > > diff --git a/drivers/gpu/drm/i915/i915_scheduler.c b/drivers/gpu/drm/i915/i915_scheduler.c > index 5d96cfba40f8..9cbd31443eb0 100644 > --- a/drivers/gpu/drm/i915/i915_scheduler.c > +++ b/drivers/gpu/drm/i915/i915_scheduler.c > @@ -423,8 +423,6 @@ bool __i915_sched_node_add_dependency(struct i915_sched_node *node, > > if (!node_signaled(signal)) { > INIT_LIST_HEAD(&dep->dfs_link); > - list_add(&dep->wait_link, &signal->waiters_list); > - list_add(&dep->signal_link, &node->signalers_list); > dep->signaler = signal; > dep->waiter = node; > dep->flags = flags; > @@ -434,6 +432,9 @@ bool __i915_sched_node_add_dependency(struct i915_sched_node *node, > !node_started(signal)) > node->flags |= I915_SCHED_HAS_SEMAPHORE_CHAIN; > > + list_add(&dep->signal_link, &node->signalers_list); > + list_add_rcu(&dep->wait_link, &signal->waiters_list); > + > /* > * As we do not allow WAIT to preempt inflight requests, > * once we have executed a request, along with triggering > -- > 2.25.0
diff --git a/drivers/gpu/drm/i915/gt/intel_lrc.c b/drivers/gpu/drm/i915/gt/intel_lrc.c index c196fb90c59f..b350e01d86d2 100644 --- a/drivers/gpu/drm/i915/gt/intel_lrc.c +++ b/drivers/gpu/drm/i915/gt/intel_lrc.c @@ -1615,6 +1615,11 @@ last_active(const struct intel_engine_execlists *execlists) return *last; } +#define for_each_waiter(p__, rq__) \ + list_for_each_entry_lockless(p__, \ + &(rq__)->sched.waiters_list, \ + wait_link) + static void defer_request(struct i915_request *rq, struct list_head * const pl) { LIST_HEAD(list); @@ -1632,7 +1637,7 @@ static void defer_request(struct i915_request *rq, struct list_head * const pl) GEM_BUG_ON(i915_request_is_active(rq)); list_move_tail(&rq->sched.link, pl); - list_for_each_entry(p, &rq->sched.waiters_list, wait_link) { + for_each_waiter(p, rq) { struct i915_request *w = container_of(p->waiter, typeof(*w), sched); diff --git a/drivers/gpu/drm/i915/i915_scheduler.c b/drivers/gpu/drm/i915/i915_scheduler.c index 5d96cfba40f8..9cbd31443eb0 100644 --- a/drivers/gpu/drm/i915/i915_scheduler.c +++ b/drivers/gpu/drm/i915/i915_scheduler.c @@ -423,8 +423,6 @@ bool __i915_sched_node_add_dependency(struct i915_sched_node *node, if (!node_signaled(signal)) { INIT_LIST_HEAD(&dep->dfs_link); - list_add(&dep->wait_link, &signal->waiters_list); - list_add(&dep->signal_link, &node->signalers_list); dep->signaler = signal; dep->waiter = node; dep->flags = flags; @@ -434,6 +432,9 @@ bool __i915_sched_node_add_dependency(struct i915_sched_node *node, !node_started(signal)) node->flags |= I915_SCHED_HAS_SEMAPHORE_CHAIN; + list_add(&dep->signal_link, &node->signalers_list); + list_add_rcu(&dep->wait_link, &signal->waiters_list); + /* * As we do not allow WAIT to preempt inflight requests, * once we have executed a request, along with triggering
Mika spotted <4>[17436.705441] general protection fault: 0000 [#1] PREEMPT SMP PTI <4>[17436.705447] CPU: 2 PID: 0 Comm: swapper/2 Not tainted 5.5.0+ #1 <4>[17436.705449] Hardware name: System manufacturer System Product Name/Z170M-PLUS, BIOS 3805 05/16/2018 <4>[17436.705512] RIP: 0010:__execlists_submission_tasklet+0xc4d/0x16e0 [i915] <4>[17436.705516] Code: c5 4c 8d 60 e0 75 17 e9 8c 07 00 00 49 8b 44 24 20 49 39 c5 4c 8d 60 e0 0f 84 7a 07 00 00 49 8b 5c 24 08 49 8b 87 80 00 00 00 <48> 39 83 d8 fe ff ff 75 d9 48 8b 83 88 fe ff ff a8 01 0f 84 b6 05 <4>[17436.705518] RSP: 0018:ffffc9000012ce80 EFLAGS: 00010083 <4>[17436.705521] RAX: ffff88822ae42000 RBX: 5a5a5a5a5a5a5a5a RCX: dead000000000122 <4>[17436.705523] RDX: ffff88822ae42588 RSI: ffff8881e32a7908 RDI: ffff8881c429fd48 <4>[17436.705525] RBP: ffffc9000012cf00 R08: ffff88822ae42588 R09: 00000000fffffffe <4>[17436.705527] R10: ffff8881c429fb80 R11: 00000000a677cf08 R12: ffff8881c42a0aa8 <4>[17436.705529] R13: ffff8881c429fd38 R14: ffff88822ae42588 R15: ffff8881c429fb80 <4>[17436.705532] FS: 0000000000000000(0000) GS:ffff88822ed00000(0000) knlGS:0000000000000000 <4>[17436.705534] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 <4>[17436.705536] CR2: 00007f858c76d000 CR3: 0000000005610003 CR4: 00000000003606e0 <4>[17436.705538] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 <4>[17436.705540] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 <4>[17436.705542] Call Trace: <4>[17436.705545] <IRQ> <4>[17436.705603] execlists_submission_tasklet+0xc0/0x130 [i915] which is us consuming a partially initialised new waiter in defer_requests(). We can prevent this by initialising the i915_dependency prior to making it visible, and since we are using a concurrent list_add/iterator mark them up to the compiler. Fixes: 8ee36e048c98 ("drm/i915/execlists: Minimalistic timeslicing") Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk> Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com> --- drivers/gpu/drm/i915/gt/intel_lrc.c | 7 ++++++- drivers/gpu/drm/i915/i915_scheduler.c | 5 +++-- 2 files changed, 9 insertions(+), 3 deletions(-)