| Message ID | 20220208020716.2140157-1-John.C.Harrison@Intel.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | drm/i915/guc: Fix flag query to not modify state | expand |
On 08/02/2022 02:07, John.C.Harrison@Intel.com wrote: > From: John Harrison <John.C.Harrison@Intel.com> > > A flag query helper was actually writing to the flags word rather than > just reading. Fix that. Also update the function's comment as it was > out of date. > > Fixes: 0f7976506de61 ("drm/i915/guc: Rework and simplify locking") > Signed-off-by: John Harrison <john.c.harrison@intel.com> > --- > drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c | 7 ++----- > 1 file changed, 2 insertions(+), 5 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 b3a429a92c0d..d9f4218f5ef4 100644 > --- a/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c > +++ b/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c > @@ -174,11 +174,8 @@ static inline void init_sched_state(struct intel_context *ce) > __maybe_unused > static bool sched_state_is_init(struct intel_context *ce) > { > - /* > - * XXX: Kernel contexts can have SCHED_STATE_NO_LOCK_REGISTERED after > - * suspend. > - */ > - return !(ce->guc_state.sched_state &= > + /* Kernel contexts can have SCHED_STATE_REGISTERED after suspend. */ > + return !(ce->guc_state.sched_state & > ~(SCHED_STATE_BLOCKED_MASK | SCHED_STATE_REGISTERED)); > } > Looks important - what are the consequences? Needs Cc: stable for 5.16? Regards, Tvrtko
On 2/8/2022 01:39, Tvrtko Ursulin wrote: > On 08/02/2022 02:07, John.C.Harrison@Intel.com wrote: >> From: John Harrison <John.C.Harrison@Intel.com> >> >> A flag query helper was actually writing to the flags word rather than >> just reading. Fix that. Also update the function's comment as it was >> out of date. >> >> Fixes: 0f7976506de61 ("drm/i915/guc: Rework and simplify locking") >> Signed-off-by: John Harrison <john.c.harrison@intel.com> >> --- >> drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c | 7 ++----- >> 1 file changed, 2 insertions(+), 5 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 b3a429a92c0d..d9f4218f5ef4 100644 >> --- a/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c >> +++ b/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c >> @@ -174,11 +174,8 @@ static inline void init_sched_state(struct >> intel_context *ce) >> __maybe_unused >> static bool sched_state_is_init(struct intel_context *ce) >> { >> - /* >> - * XXX: Kernel contexts can have SCHED_STATE_NO_LOCK_REGISTERED >> after >> - * suspend. >> - */ >> - return !(ce->guc_state.sched_state &= >> + /* Kernel contexts can have SCHED_STATE_REGISTERED after >> suspend. */ >> + return !(ce->guc_state.sched_state & >> ~(SCHED_STATE_BLOCKED_MASK | SCHED_STATE_REGISTERED)); >> } > > Looks important - what are the consequences? Supposedly nothing. The test was only ever used inside a BUG_ON during context registration. Rather than asserting that the condition was true, it was making the condition true. So, in theory, there was no consequence because we should never have hit a BUG_ON anyway. Which means the write should always have been a no-op. > > Needs Cc: stable for 5.16? Meaning "Cc: <stable@vger.kernel.org>"? Or is there anything required to specify 5.16? John. > > Regards, > > Tvrtko
On 08/02/2022 18:53, John Harrison wrote: > On 2/8/2022 01:39, Tvrtko Ursulin wrote: >> On 08/02/2022 02:07, John.C.Harrison@Intel.com wrote: >>> From: John Harrison <John.C.Harrison@Intel.com> >>> >>> A flag query helper was actually writing to the flags word rather than >>> just reading. Fix that. Also update the function's comment as it was >>> out of date. >>> >>> Fixes: 0f7976506de61 ("drm/i915/guc: Rework and simplify locking") >>> Signed-off-by: John Harrison <john.c.harrison@intel.com> >>> --- >>> drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c | 7 ++----- >>> 1 file changed, 2 insertions(+), 5 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 b3a429a92c0d..d9f4218f5ef4 100644 >>> --- a/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c >>> +++ b/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c >>> @@ -174,11 +174,8 @@ static inline void init_sched_state(struct >>> intel_context *ce) >>> __maybe_unused >>> static bool sched_state_is_init(struct intel_context *ce) >>> { >>> - /* >>> - * XXX: Kernel contexts can have SCHED_STATE_NO_LOCK_REGISTERED >>> after >>> - * suspend. >>> - */ >>> - return !(ce->guc_state.sched_state &= >>> + /* Kernel contexts can have SCHED_STATE_REGISTERED after >>> suspend. */ >>> + return !(ce->guc_state.sched_state & >>> ~(SCHED_STATE_BLOCKED_MASK | SCHED_STATE_REGISTERED)); >>> } >> >> Looks important - what are the consequences? > Supposedly nothing. > > The test was only ever used inside a BUG_ON during context registration. > Rather than asserting that the condition was true, it was making the > condition true. So, in theory, there was no consequence because we > should never have hit a BUG_ON anyway. Which means the write should > always have been a no-op. > >> >> Needs Cc: stable for 5.16? > Meaning "Cc: <stable@vger.kernel.org>"? Or is there anything required to > specify 5.16? It would have been: Cc: <stable@vger.kernel.org> # v5.16+ You can use "dim fixes <sha>" and it will output you the suggested tags. But given what you say about it having no impact even in debug builds then it's not needed. Just note that explaining the impact in the commit message when Fixes: tag is present is very desirable in general. Without it maintainers have a hard time assessing and highlighting important stuff in pull requests. So I would at least ask for respin with updated commit message explaining there is no consequence and why cc stable is not needed. Regards, Tvrtko
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 b3a429a92c0d..d9f4218f5ef4 100644 --- a/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c +++ b/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c @@ -174,11 +174,8 @@ static inline void init_sched_state(struct intel_context *ce) __maybe_unused static bool sched_state_is_init(struct intel_context *ce) { - /* - * XXX: Kernel contexts can have SCHED_STATE_NO_LOCK_REGISTERED after - * suspend. - */ - return !(ce->guc_state.sched_state &= + /* Kernel contexts can have SCHED_STATE_REGISTERED after suspend. */ + return !(ce->guc_state.sched_state & ~(SCHED_STATE_BLOCKED_MASK | SCHED_STATE_REGISTERED)); }