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drm/i915/execlists: Pull tasklet interrupt-bh local to direct submission

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We dropped calling process_csb prior to handling direct submission in
order to avoid the nesting of spinlocks and lift process_csb() and the
majority of the tasklet out of irq-off. However, we do want to avoid
ksoftirqd latency in the fast path, so try and pull the interrupt-bh
local to direct submission if we can acquire the tasklet's lock.

v2: Document the read of pending[0] from outside the tasklet with
READ_ONCE.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200325120227.8044-1-chris@chris-wilson.co.uk
This commit is contained in:
Chris Wilson
2020-03-25 12:02:26 +00:00
parent 032d992dcb
commit 6670b413f8
1 changed files with 7 additions and 0 deletions
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7
drivers/gpu/drm/i915/gt/intel_lrc.c
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@@ -2891,6 +2891,13 @@ static void __submit_queue_imm(struct intel_engine_cs *engine)
if (reset_in_progress(execlists))
return; /* defer until we restart the engine following reset */
/* Hopefully we clear execlists->pending[] to let us through */
if (READ_ONCE(execlists->pending[0]) &&
tasklet_trylock(&execlists->tasklet)) {
process_csb(engine);
tasklet_unlock(&execlists->tasklet);
}
__execlists_submission_tasklet(engine);
}