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| author |   Chris Wilson <chris@chris-wilson.co.uk> | 2017-04-04 13:05:31 +0100 |
|---|---|---|
| committer | Chris Wilson <chris@chris-wilson.co.uk> | 2017-04-04 13:48:21 +0100 |
| commit | a7980a640cbd339aa80f406d1786a275a2c320bc (patch) | |
| tree | 48e7c5bf1a70b1a471657b5e5097de71a4ecd01c /drivers/gpu/drm/i915/intel_breadcrumbs.c | |
| parent | drm/i915: Park the signaler before sleeping (diff) | |
| download | linux-dev-a7980a640cbd339aa80f406d1786a275a2c320bc.tar.xz linux-dev-a7980a640cbd339aa80f406d1786a275a2c320bc.zip | |
drm/i915: Apply a cond_resched() to the saturated signaler
If the engine is continually completing nops, we can saturate the
signaler and keep it working indefinitely. This angers the NMI watchdog!
A good example is to disable semaphores on snb and run igt/gem_exec_nop -
the parallel, multi-engine workloads are more than sufficient to hog the
CPU, preventing the system from even processing ICMP echo replies.
v2: Tvrtko dug into cond_resched() on x86 and found that it only
depended upon preempt_count and not tif_need_resched() - which means
that we would always call schedule() at that point.
Fixes: c81d46138da6 ("drm/i915: Convert trace-irq to the breadcrumb waiter")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Mika Kuoppala <mika.kuoppala@intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170404120531.10737-1-chris@chris-wilson.co.uk
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Diffstat (limited to 'drivers/gpu/drm/i915/intel_breadcrumbs.c')
| -rw-r--r-- | drivers/gpu/drm/i915/intel_breadcrumbs.c | 15 |
1 files changed, 14 insertions, 1 deletions
diff --git a/drivers/gpu/drm/i915/intel_breadcrumbs.c b/drivers/gpu/drm/i915/intel_breadcrumbs.c index 308c56a021ab..9ccbf26124c6 100644 --- a/drivers/gpu/drm/i915/intel_breadcrumbs.c +++ b/drivers/gpu/drm/i915/intel_breadcrumbs.c @@ -580,6 +580,8 @@ static int intel_breadcrumbs_signaler(void *arg) signaler_set_rtpriority(); do { + bool do_schedule = true; + set_current_state(TASK_INTERRUPTIBLE); /* We are either woken up by the interrupt bottom-half, @@ -626,7 +628,18 @@ static int intel_breadcrumbs_signaler(void *arg) spin_unlock_irq(&b->rb_lock); i915_gem_request_put(request); - } else { + + /* If the engine is saturated we may be continually + * processing completed requests. This angers the + * NMI watchdog if we never let anything else + * have access to the CPU. Let's pretend to be nice + * and relinquish the CPU if we burn through the + * entire RT timeslice! + */ + do_schedule = need_resched(); + } + + if (unlikely(do_schedule)) { DEFINE_WAIT(exec); if (kthread_should_park()) |