On 20/11/2020 14:32, Chris Wilson wrote:
Quoting Tvrtko Ursulin (2020-11-20 09:56:36)
From: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
CT event handler is called under the gt->irq_lock from the interrupt
handling paths so make it the same from the init path. I don't think this
mismatch caused any functional issue but we need to wean the code of the
global i915->irq_lock.
ct_read definitely wants to be serialised. Is guc->irq_lock the right
choice?
Not under my understanding and also confirmed by Daniele off line.
Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
Cc: Daniele Ceraolo Spurio <daniele.ceraolospurio@xxxxxxxxx>
---
drivers/gpu/drm/i915/gt/uc/intel_uc.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)
diff --git a/drivers/gpu/drm/i915/gt/uc/intel_uc.c b/drivers/gpu/drm/i915/gt/uc/intel_uc.c
index 220626c3ad81..6a0452815c41 100644
--- a/drivers/gpu/drm/i915/gt/uc/intel_uc.c
+++ b/drivers/gpu/drm/i915/gt/uc/intel_uc.c
@@ -203,7 +203,8 @@ static void guc_disable_interrupts(struct intel_guc *guc)
static int guc_enable_communication(struct intel_guc *guc)
{
- struct drm_i915_private *i915 = guc_to_gt(guc)->i915;
+ struct intel_gt *gt = guc_to_gt(guc);
+ struct drm_i915_private *i915 = gt->i915;
int ret;
GEM_BUG_ON(guc_communication_enabled(guc));
@@ -223,9 +224,9 @@ static int guc_enable_communication(struct intel_guc *guc)
guc_enable_interrupts(guc);
/* check for CT messages received before we enabled interrupts */
- spin_lock_irq(&i915->irq_lock);
+ spin_lock_irq(>->irq_lock);
intel_guc_ct_event_handler(&guc->ct);
- spin_unlock_irq(&i915->irq_lock);
+ spin_unlock_irq(>->irq_lock);
You used guc->irq_lock in the previous patch. I suggest
intel_guc_ct_event_handler() should specify what lock it requires.
There are indeed too many locks and too little asserts to help the reader.
But the other end of the state ct_read needs is updated from the GuC
firmware itself, which then send the interrupt, which we process in:
guc_irq_handler
-> intel_guc_to_host_event_handler
-> intel_guc_ct_event_handler
And this side runs under the gt->irq_lock.
Regards,
Tvrtko
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