[Intel-gfx] [PATCH 08/15] drm/i915: Combine tasklet_kill and tasklet_disable

[Chris Wilson]

Ideally, we want to atomically flush and disable the tasklet before
resetting the GPU. At present, we rely on being the only part to touch
our tasklet and serialisation of the reset process to ensure that we can
suspend the tasklet from the mix of reset/wedge pathways. In this patch,
we move the tasklet abuse into its own function and tweak it such that
we only do a synchronous operation the first time it is disabled around
the reset. This allows us to avoid the sync inside a softirq context in
subsequent patches.

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
Cc: Mika Kuoppala <mika.kuoppala at linux.intel.com>
Cc: Michał Winiarski <michal.winiarski at intel.com>
CC: Michel Thierry <michel.thierry at intel.com>
Cc: Jeff McGee <jeff.mcgee at intel.com>
---
 drivers/gpu/drm/i915/intel_lrc.c | 14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c
index 7aecf8b37139..be1737d42d43 100644
--- a/drivers/gpu/drm/i915/intel_lrc.c
+++ b/drivers/gpu/drm/i915/intel_lrc.c
@@ -1722,6 +1722,16 @@ static int gen9_init_render_ring(struct intel_engine_cs *engine)
 	return init_workarounds_ring(engine);
 }
 
+static void tasklet_kill_and_disable(struct tasklet_struct *t)
+{
+	if (!atomic_read(&t->count))
+		tasklet_kill(t);
+
+	if (atomic_inc_return(&t->count) == 1)
+		tasklet_unlock_wait(t);
+	smp_mb();
+}
+
 static struct i915_request *
 execlists_reset_prepare(struct intel_engine_cs *engine)
 {
@@ -1746,9 +1756,7 @@ execlists_reset_prepare(struct intel_engine_cs *engine)
 	 * common case of recursively being called from set-wedged from inside
 	 * i915_reset.
 	 */
-	if (!atomic_read(&execlists->tasklet.count))
-		tasklet_kill(&execlists->tasklet);
-	tasklet_disable(&execlists->tasklet);
+	tasklet_kill_and_disable(&execlists->tasklet);
 
 	/*
 	 * We want to flush the pending context switches, having disabled
-- 
2.16.3