AcoSail/kernel_optimize_test
8
0
Fork 0
forked from luck/tmp_suning_uos_patched
Code Pull Requests Activity

drm/i915: Skip signaling a signaled request

Browse Source 
Preempt-to-busy introduces various fascinating complications in that the
requests may complete as we are unsubmitting them from HW. As they may
then signal after unsubmission, we may find ourselves having to cleanup
the signaling request from within the signaling callback. This causes us
to recurse onto the same i915_request.lock.

However, if the request is already signaled (as it will be before we
enter the signal callbacks), we know we can skip the signaling of that
request during submission, neatly evading the spinlock recursion.

unsubmit(ve.rq0) # timeslice expiration or other preemption
 -> virtual_submit_request(ve.rq0)
dma_fence_signal(ve.rq0) # request completed before preemption ack
 -> submit_notify(ve.rq1)
   -> virtual_submit_request(ve.rq1) # sees that we have completed ve.rq0
      -> __i915_request_submit(ve.rq0)

[  264.210142] BUG: spinlock recursion on CPU#2, sample_multi_tr/2093
[  264.210150]  lock: 0xffff9efd6ac55080, .magic: dead4ead, .owner: sample_multi_tr/2093, .owner_cpu: 2
[  264.210155] CPU: 2 PID: 2093 Comm: sample_multi_tr Tainted: G     U
[  264.210158] Hardware name: Intel Corporation CoffeeLake Client Platform/CoffeeLake S UDIMM RVP, BIOS CNLSFWR1.R00.X212.B01.1909060036 09/06/2019
[  264.210160] Call Trace:
[  264.210167]  dump_stack+0x98/0xda
[  264.210174]  spin_dump.cold+0x24/0x3c
[  264.210178]  do_raw_spin_lock+0x9a/0xd0
[  264.210184]  _raw_spin_lock_nested+0x6a/0x70
[  264.210314]  __i915_request_submit+0x10a/0x3c0 [i915]
[  264.210415]  virtual_submit_request+0x9b/0x380 [i915]
[  264.210516]  submit_notify+0xaf/0x14c [i915]
[  264.210602]  __i915_sw_fence_complete+0x8a/0x230 [i915]
[  264.210692]  i915_sw_fence_complete+0x2d/0x40 [i915]
[  264.210762]  __dma_i915_sw_fence_wake+0x19/0x30 [i915]
[  264.210767]  dma_fence_signal_locked+0xb1/0x1c0
[  264.210772]  dma_fence_signal+0x29/0x50
[  264.210871]  i915_request_wait+0x5cb/0x830 [i915]
[  264.210876]  ? dma_resv_get_fences_rcu+0x294/0x5d0
[  264.210974]  i915_gem_object_wait_fence+0x2f/0x40 [i915]
[  264.211084]  i915_gem_object_wait+0xce/0x400 [i915]
[  264.211178]  i915_gem_wait_ioctl+0xff/0x290 [i915]

Fixes: 22b7a426bb ("drm/i915/execlists: Preempt-to-busy")
References: 6d06779e86 ("drm/i915: Load balancing across a virtual engine")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: "Nayana, Venkata Ramana" <venkata.ramana.nayana@intel.com>
Cc: <stable@vger.kernel.org> # v5.4+
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200713141636.29326-1-chris@chris-wilson.co.uk
This commit is contained in:
Chris Wilson 2020-07-13 15:16:36 +01:00
parent 90a987205c
commit 1d9221e9d3
2 changed files with 19 additions and 11 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

7
drivers/gpu/drm/i915/gt/intel_breadcrumbs.c
View File

@ -314,13 +314,18 @@ bool i915_request_enable_breadcrumb(struct i915_request *rq)
{
lockdep_assert_held(&rq->lock);
if (test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &rq->fence.flags))
return true;
if (test_bit(I915_FENCE_FLAG_ACTIVE, &rq->fence.flags)) {
struct intel_breadcrumbs *b = &rq->engine->breadcrumbs;
struct intel_context *ce = rq->context;
struct list_head *pos;
spin_lock(&b->irq_lock);
GEM_BUG_ON(test_bit(I915_FENCE_FLAG_SIGNAL, &rq->fence.flags));
if (test_bit(I915_FENCE_FLAG_SIGNAL, &rq->fence.flags))
goto unlock;
if (!__intel_breadcrumbs_arm_irq(b))
goto unlock;

23
drivers/gpu/drm/i915/i915_request.c
View File

@ -560,22 +560,25 @@ bool __i915_request_submit(struct i915_request *request)
engine->serial++;
result = true;
xfer: /* We may be recursing from the signal callback of another i915 fence */
spin_lock_nested(&request->lock, SINGLE_DEPTH_NESTING);
xfer:
if (!test_and_set_bit(I915_FENCE_FLAG_ACTIVE, &request->fence.flags)) {
list_move_tail(&request->sched.link, &engine->active.requests);
clear_bit(I915_FENCE_FLAG_PQUEUE, &request->fence.flags);
__notify_execute_cb(request);
}
GEM_BUG_ON(!llist_empty(&request->execute_cb));
if (test_bit(DMA_FENCE_FLAG_ENABLE_SIGNAL_BIT, &request->fence.flags) &&
!test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &request->fence.flags) &&
!i915_request_enable_breadcrumb(request))
intel_engine_signal_breadcrumbs(engine);
/* We may be recursing from the signal callback of another i915 fence */
if (!i915_request_signaled(request)) {
spin_lock_nested(&request->lock, SINGLE_DEPTH_NESTING);
spin_unlock(&request->lock);
__notify_execute_cb(request);
if (test_bit(DMA_FENCE_FLAG_ENABLE_SIGNAL_BIT,
&request->fence.flags) &&
!i915_request_enable_breadcrumb(request))
intel_engine_signal_breadcrumbs(engine);
spin_unlock(&request->lock);
GEM_BUG_ON(!llist_empty(&request->execute_cb));
}
return result;
}