[Intel-gfx] [PATCH 04/31] drm/i915/execlists: Pull CSB reset under the timeline.lock

[Chris Wilson]

In the following patch, we will process the CSB events under the
timeline.lock and not serailiased by the tasklet. This also means that we
will need to protect access to common variables such as
execlists->csb_head with the timeline.lock during reset.

v2: Move sync_irq to avoid deadlocks between taking timeline.lock from
our interrupt handler.

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
---
 drivers/gpu/drm/i915/intel_lrc.c | 11 +++++------
 1 file changed, 5 insertions(+), 6 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c
index b5c809201c7a..2cbb293fb409 100644
--- a/drivers/gpu/drm/i915/intel_lrc.c
+++ b/drivers/gpu/drm/i915/intel_lrc.c
@@ -871,7 +871,6 @@ static void reset_irq(struct intel_engine_cs *engine)
 {
 	/* Mark all CS interrupts as complete */
 	smp_store_mb(engine->execlists.active, 0);
-	synchronize_hardirq(engine->i915->drm.irq);
 
 	clear_gtiir(engine);
 
@@ -912,6 +911,8 @@ static void execlists_cancel_requests(struct intel_engine_cs *engine)
 
 	/* Cancel the requests on the HW and clear the ELSP tracker. */
 	execlists_cancel_port_requests(execlists);
+
+	synchronize_hardirq(engine->i915->drm.irq);
 	reset_irq(engine);
 
 	spin_lock(&engine->timeline.lock);
@@ -1969,8 +1970,8 @@ static void execlists_reset(struct intel_engine_cs *engine,
 		  engine->name, request ? request->global_seqno : 0,
 		  intel_engine_get_seqno(engine));
 
-	/* See execlists_cancel_requests() for the irq/spinlock split. */
-	local_irq_save(flags);
+	synchronize_hardirq(engine->i915->drm.irq);
+	spin_lock_irqsave(&engine->timeline.lock, flags);
 
 	/*
 	 * Catch up with any missed context-switch interrupts.
@@ -1985,14 +1986,12 @@ static void execlists_reset(struct intel_engine_cs *engine,
 	reset_irq(engine);
 
 	/* Push back any incomplete requests for replay after the reset. */
-	spin_lock(&engine->timeline.lock);
 	__unwind_incomplete_requests(engine);
-	spin_unlock(&engine->timeline.lock);
 
 	/* Following the reset, we need to reload the CSB read/write pointers */
 	engine->execlists.csb_head = GEN8_CSB_ENTRIES - 1;
 
-	local_irq_restore(flags);
+	spin_unlock_irqrestore(&engine->timeline.lock, flags);
 
 	/*
 	 * If the request was innocent, we leave the request in the ELSP
-- 
2.18.0