On 8/18/2021 11:16 PM, Matthew Brost wrote:
Before we did some clever tricks to not use the a lock when touching
guc_state.sched_state in certain cases. Don't do that, enforce the use
of the lock.
Part of this is removing a dead code path from guc_lrc_desc_pin where a
context could be deregistered when the aforementioned function was
called from the submission path. Remove this dead code and add a
GEM_BUG_ON if this path is ever attempted to be used.
v2:
(kernel test robo )
- Add __maybe_unused to sched_state_is_init()
Signed-off-by: Matthew Brost <matthew.brost@xxxxxxxxx>
Reported-by: kernel test robot <lkp@xxxxxxxxx>
---
.../gpu/drm/i915/gt/uc/intel_guc_submission.c | 58 ++++++++++---------
1 file changed, 32 insertions(+), 26 deletions(-)
diff --git a/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c b/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
index 85f96d325048..fa87470ea576 100644
--- a/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
+++ b/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
@@ -150,11 +150,23 @@ static inline void clr_context_registered(struct intel_context *ce)
#define SCHED_STATE_BLOCKED_MASK (0xfff << SCHED_STATE_BLOCKED_SHIFT)
static inline void init_sched_state(struct intel_context *ce)
{
- /* Only should be called from guc_lrc_desc_pin() */
+ lockdep_assert_held(&ce->guc_state.lock);
atomic_set(&ce->guc_sched_state_no_lock, 0);
ce->guc_state.sched_state &= SCHED_STATE_BLOCKED_MASK;
}
+__maybe_unused
+static bool sched_state_is_init(struct intel_context *ce)
+{
+ /*
+ * XXX: Kernel contexts can have SCHED_STATE_NO_LOCK_REGISTERED after
+ * suspend.
+ */
This seems like something we want to fix. Not a blocker for this, but we
can add it to the list.
+ return !(atomic_read(&ce->guc_sched_state_no_lock) &
+ ~SCHED_STATE_NO_LOCK_REGISTERED) &&
+ !(ce->guc_state.sched_state &= ~SCHED_STATE_BLOCKED_MASK);
+}
+
static inline bool
context_wait_for_deregister_to_register(struct intel_context *ce)
{
@@ -165,7 +177,7 @@ context_wait_for_deregister_to_register(struct intel_context *ce)
static inline void
set_context_wait_for_deregister_to_register(struct intel_context *ce)
{
- /* Only should be called from guc_lrc_desc_pin() without lock */
+ lockdep_assert_held(&ce->guc_state.lock);
ce->guc_state.sched_state |=
SCHED_STATE_WAIT_FOR_DEREGISTER_TO_REGISTER;
}
@@ -605,9 +617,7 @@ static void scrub_guc_desc_for_outstanding_g2h(struct intel_guc *guc)
bool pending_disable, pending_enable, deregister, destroyed, banned;
xa_for_each(&guc->context_lookup, index, ce) {
- /* Flush context */
spin_lock_irqsave(&ce->guc_state.lock, flags);
- spin_unlock_irqrestore(&ce->guc_state.lock, flags);
/*
* Once we are at this point submission_disabled() is guaranteed
@@ -623,6 +633,8 @@ static void scrub_guc_desc_for_outstanding_g2h(struct intel_guc *guc)
banned = context_banned(ce);
init_sched_state(ce);
+ spin_unlock_irqrestore(&ce->guc_state.lock, flags);
+
if (pending_enable || destroyed || deregister) {
decr_outstanding_submission_g2h(guc);
if (deregister)
@@ -1325,6 +1337,7 @@ static int guc_lrc_desc_pin(struct intel_context *ce, bool loop)
int ret = 0;
GEM_BUG_ON(!engine->mask);
+ GEM_BUG_ON(!sched_state_is_init(ce));
/*
* Ensure LRC + CT vmas are is same region as write barrier is done
@@ -1353,7 +1366,6 @@ static int guc_lrc_desc_pin(struct intel_context *ce, bool loop)
desc->priority = ce->guc_prio;
desc->context_flags = CONTEXT_REGISTRATION_FLAG_KMD;
guc_context_policy_init(engine, desc);
- init_sched_state(ce);
/*
* The context_lookup xarray is used to determine if the hardware
@@ -1364,26 +1376,23 @@ static int guc_lrc_desc_pin(struct intel_context *ce, bool loop)
* registering this context.
*/
if (context_registered) {
+ bool disabled;
+ unsigned long flags;
+
trace_intel_context_steal_guc_id(ce);
- if (!loop) {
+ GEM_BUG_ON(!loop);
+
+ /* Seal race with Reset */
+ spin_lock_irqsave(&ce->guc_state.lock, flags);
+ disabled = submission_disabled(guc);
+ if (likely(!disabled)) {
set_context_wait_for_deregister_to_register(ce);
intel_context_get(ce);
- } else {
- bool disabled;
- unsigned long flags;
-
- /* Seal race with Reset */
- spin_lock_irqsave(&ce->guc_state.lock, flags);
- disabled = submission_disabled(guc);
- if (likely(!disabled)) {
- set_context_wait_for_deregister_to_register(ce);
- intel_context_get(ce);
- }
- spin_unlock_irqrestore(&ce->guc_state.lock, flags);
- if (unlikely(disabled)) {
- reset_lrc_desc(guc, desc_idx);
- return 0; /* Will get registered later */
- }
+ }
+ spin_unlock_irqrestore(&ce->guc_state.lock, flags);
+ if (unlikely(disabled)) {
+ reset_lrc_desc(guc, desc_idx);
+ return 0; /* Will get registered later */
}
/*
@@ -1392,10 +1401,7 @@ static int guc_lrc_desc_pin(struct intel_context *ce, bool loop)
*/
with_intel_runtime_pm(runtime_pm, wakeref)
ret = deregister_context(ce, ce->guc_id, loop);
- if (unlikely(ret == -EBUSY)) {
- clr_context_wait_for_deregister_to_register(ce);
- intel_context_put(ce);
Why is the EBUSY case not applicable anymore?
Daniele
- } else if (unlikely(ret == -ENODEV)) {
+ if (unlikely(ret == -ENODEV)) {
ret = 0; /* Will get registered later */
}
} else {
