Re: [PATCH] drm/i915: Improve user experience and driver robustness under SIGINT or similar

[Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxxxxxxxx>]

Final call to raise objections.

Regards,

Tvrtko

On 07/06/2022 09:36, Tvrtko Ursulin wrote:
> On 27/05/2022 13:07, Andrzej Hajda wrote:
> > On 27.05.2022 09:24, Tvrtko Ursulin wrote:
> > > From: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
> > >
> > > We have long standing customer complaints that pressing Ctrl-C (or to 
> > > the
> > > effect of) causes engine resets with otherwise well behaving programs.
> > >
> > > Not only is logging engine resets during normal operation not desirable
> > > since it creates support incidents, but more fundamentally we should 
> > > avoid
> > > going the engine reset path when we can since any engine reset 
> > > introduces
> > > a chance of harming an innocent context.
> > >
> > > Reason for this undesirable behaviour is that the driver currently does
> > > not distinguish between banned contexts and non-persistent contexts 
> > > which
> > > have been closed.
> > >
> > > To fix this we add the distinction between the two reasons for revoking
> > > contexts, which then allows the strict timeout only be applied to 
> > > banned,
> > > while innocent contexts (well behaving) can preempt cleanly and exit
> > > without triggering the engine reset path.
> > >
> > > Note that the added context exiting category applies both to closed non-
> > > persistent context, and any exiting context when hangcheck has been
> > > disabled by the user.
> > >
> > > At the same time we rename the backend operation from 'ban' to 'revoke'
> > > which more accurately describes the actual semantics. (There is no 
> > > ban at
> > > the backend level since banning is a concept driven by the scheduling
> > > frontend. Backends are simply able to revoke a running context so that
> > > is the more appropriate name chosen.)
> > >
> > > Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
> > > ---
> > >   drivers/gpu/drm/i915/gem/i915_gem_context.c   | 23 +++++++++++------
> > >   drivers/gpu/drm/i915/gt/intel_context.c       | 24 ++++++++++++++++++
> > >   drivers/gpu/drm/i915/gt/intel_context.h       | 25 +++++++++++++------
> > >   drivers/gpu/drm/i915/gt/intel_context_types.h |  4 ++-
> > >   .../drm/i915/gt/intel_execlists_submission.c  |  6 ++---
> > >   .../gpu/drm/i915/gt/intel_ring_submission.c   |  7 +++---
> > >   .../gpu/drm/i915/gt/uc/intel_guc_submission.c | 15 ++++++-----
> > >   drivers/gpu/drm/i915/i915_request.c           |  2 +-
> > >   8 files changed, 77 insertions(+), 29 deletions(-)
> > >
> > > diff --git a/drivers/gpu/drm/i915/gem/i915_gem_context.c 
> > > b/drivers/gpu/drm/i915/gem/i915_gem_context.c
> > > index ab4c5ab28e4d..6b171c89b1b3 100644
> > > --- a/drivers/gpu/drm/i915/gem/i915_gem_context.c
> > > +++ b/drivers/gpu/drm/i915/gem/i915_gem_context.c
> > > @@ -1367,7 +1367,8 @@ static struct intel_engine_cs 
> > > *active_engine(struct intel_context *ce)
> > >       return engine;
> > >   }
> > > -static void kill_engines(struct i915_gem_engines *engines, bool ban)
> > > +static void
> > > +kill_engines(struct i915_gem_engines *engines, bool exit, bool 
> > > persistent)
> > >   {
> > >       struct i915_gem_engines_iter it;
> > >       struct intel_context *ce;
> > > @@ -1381,9 +1382,15 @@ static void kill_engines(struct 
> > > i915_gem_engines *engines, bool ban)
> > >        */
> > >       for_each_gem_engine(ce, engines, it) {
> > >           struct intel_engine_cs *engine;
> > > +        bool skip = false;
> > > -        if (ban && intel_context_ban(ce, NULL))
> > > -            continue;
> > > +        if (exit)
> > > +            skip = intel_context_set_exiting(ce);
> > > +        else if (!persistent)
> > > +            skip = intel_context_exit_nonpersistent(ce, NULL);
> > > +
> > > +        if (skip)
> > > +            continue; /* Already marked. */
> >
> > why not:
> >      if (exit && intel_context_set_exiting(ce))
> >          continue;
> >      else if (!persistent && intel_context_exit_nonpersistent(ce, NULL)
> >          continue;
>
> Just so I can put the "already marked" comment on single line.
>
> > Anyway:
> > Reviewed-by: Andrzej Hajda <andrzej.hajda@xxxxxxxxx>
>
> Thanks!
>
> John, Daniel - you had reservations against the older version of this 
> patch AFAIR. This time round I believe I conceptually simplified it by 
> doing a clean separation of contexts which should not be scheduled any 
> more becuase they want it so, versus the ones we banned. That is, the 
> patch stops abusing the banned status for contexts which haven't been 
> (banned). This allows to only apply the strict preempt timeout to 
> banned, while there is no reason to add any new timeout values for the 
> rest.
>
> Any objections to this version?
>
> Regards,
>
> Tvrtko
>
> > Regards
> > Andrzej
> >
> > >           /*
> > >            * Check the current active state of this context; if we
> > > @@ -1395,7 +1402,7 @@ static void kill_engines(struct 
> > > i915_gem_engines *engines, bool ban)
> > >           engine = active_engine(ce);
> > >           /* First attempt to gracefully cancel the context */
> > > -        if (engine && !__cancel_engine(engine) && ban)
> > > +        if (engine && !__cancel_engine(engine) && (exit || 
> > > !persistent))
> > >               /*
> > >                * If we are unable to send a preemptive pulse to bump
> > >                * the context from the GPU, we have to resort to a full
> > > @@ -1407,8 +1414,6 @@ static void kill_engines(struct 
> > > i915_gem_engines *engines, bool ban)
> > >   static void kill_context(struct i915_gem_context *ctx)
> > >   {
> > > -    bool ban = (!i915_gem_context_is_persistent(ctx) ||
> > > -            !ctx->i915->params.enable_hangcheck);
> > >       struct i915_gem_engines *pos, *next;
> > >       spin_lock_irq(&ctx->stale.lock);
> > > @@ -1421,7 +1426,8 @@ static void kill_context(struct 
> > > i915_gem_context *ctx)
> > >           spin_unlock_irq(&ctx->stale.lock);
> > > -        kill_engines(pos, ban);
> > > +        kill_engines(pos, !ctx->i915->params.enable_hangcheck,
> > > +                 i915_gem_context_is_persistent(ctx));
> > >           spin_lock_irq(&ctx->stale.lock);
> > >           GEM_BUG_ON(i915_sw_fence_signaled(&pos->fence));
> > > @@ -1467,7 +1473,8 @@ static void engines_idle_release(struct 
> > > i915_gem_context *ctx,
> > >   kill:
> > >       if (list_empty(&engines->link)) /* raced, already closed */
> > > -        kill_engines(engines, true);
> > > +        kill_engines(engines, true,
> > > +                 i915_gem_context_is_persistent(ctx));
> > >       i915_sw_fence_commit(&engines->fence);
> > >   }
> > > diff --git a/drivers/gpu/drm/i915/gt/intel_context.c 
> > > b/drivers/gpu/drm/i915/gt/intel_context.c
> > > index 4070cb5711d8..654a092ed3d6 100644
> > > --- a/drivers/gpu/drm/i915/gt/intel_context.c
> > > +++ b/drivers/gpu/drm/i915/gt/intel_context.c
> > > @@ -601,6 +601,30 @@ u64 intel_context_get_avg_runtime_ns(struct 
> > > intel_context *ce)
> > >       return avg;
> > >   }
> > > +bool intel_context_ban(struct intel_context *ce, struct i915_request 
> > > *rq)
> > > +{
> > > +    bool ret = intel_context_set_banned(ce);
> > > +
> > > +    trace_intel_context_ban(ce);
> > > +
> > > +    if (ce->ops->revoke)
> > > +        ce->ops->revoke(ce, rq,
> > > +                INTEL_CONTEXT_BANNED_PREEMPT_TIMEOUT_MS);
> > > +
> > > +    return ret;
> > > +}
> > > +
> > > +bool intel_context_exit_nonpersistent(struct intel_context *ce,
> > > +                      struct i915_request *rq)
> > > +{
> > > +    bool ret = intel_context_set_exiting(ce);
> > > +
> > > +    if (ce->ops->revoke)
> > > +        ce->ops->revoke(ce, rq, ce->engine->props.preempt_timeout_ms);
> > > +
> > > +    return ret;
> > > +}
> > > +
> > >   #if IS_ENABLED(CONFIG_DRM_I915_SELFTEST)
> > >   #include "selftest_context.c"
> > >   #endif
> > > diff --git a/drivers/gpu/drm/i915/gt/intel_context.h 
> > > b/drivers/gpu/drm/i915/gt/intel_context.h
> > > index b7d3214d2cdd..8e2d70630c49 100644
> > > --- a/drivers/gpu/drm/i915/gt/intel_context.h
> > > +++ b/drivers/gpu/drm/i915/gt/intel_context.h
> > > @@ -25,6 +25,8 @@
> > >                ##__VA_ARGS__);                    \
> > >   } while (0)
> > > +#define INTEL_CONTEXT_BANNED_PREEMPT_TIMEOUT_MS (1)
> > > +
> > >   struct i915_gem_ww_ctx;
> > >   void intel_context_init(struct intel_context *ce,
> > > @@ -309,18 +311,27 @@ static inline bool 
> > > intel_context_set_banned(struct intel_context *ce)
> > >       return test_and_set_bit(CONTEXT_BANNED, &ce->flags);
> > >   }
> > > -static inline bool intel_context_ban(struct intel_context *ce,
> > > -                     struct i915_request *rq)
> > > +bool intel_context_ban(struct intel_context *ce, struct i915_request 
> > > *rq);
> > > +
> > > +static inline bool intel_context_is_schedulable(const struct 
> > > intel_context *ce)
> > >   {
> > > -    bool ret = intel_context_set_banned(ce);
> > > +    return !test_bit(CONTEXT_EXITING, &ce->flags) &&
> > > +           !test_bit(CONTEXT_BANNED, &ce->flags);
> > > +}
> > > -    trace_intel_context_ban(ce);
> > > -    if (ce->ops->ban)
> > > -        ce->ops->ban(ce, rq);
> > > +static inline bool intel_context_is_exiting(const struct 
> > > intel_context *ce)
> > > +{
> > > +    return test_bit(CONTEXT_EXITING, &ce->flags);
> > > +}
> > > -    return ret;
> > > +static inline bool intel_context_set_exiting(struct intel_context *ce)
> > > +{
> > > +    return test_and_set_bit(CONTEXT_EXITING, &ce->flags);
> > >   }
> > > +bool intel_context_exit_nonpersistent(struct intel_context *ce,
> > > +                      struct i915_request *rq);
> > > +
> > >   static inline bool
> > >   intel_context_force_single_submission(const struct intel_context *ce)
> > >   {
> > > diff --git a/drivers/gpu/drm/i915/gt/intel_context_types.h 
> > > b/drivers/gpu/drm/i915/gt/intel_context_types.h
> > > index 09f82545789f..d2d75d9c0c8d 100644
> > > --- a/drivers/gpu/drm/i915/gt/intel_context_types.h
> > > +++ b/drivers/gpu/drm/i915/gt/intel_context_types.h
> > > @@ -40,7 +40,8 @@ struct intel_context_ops {
> > >       int (*alloc)(struct intel_context *ce);
> > > -    void (*ban)(struct intel_context *ce, struct i915_request *rq);
> > > +    void (*revoke)(struct intel_context *ce, struct i915_request *rq,
> > > +               unsigned int preempt_timeout_ms);
> > >       int (*pre_pin)(struct intel_context *ce, struct i915_gem_ww_ctx 
> > > *ww, void **vaddr);
> > >       int (*pin)(struct intel_context *ce, void *vaddr);
> > > @@ -122,6 +123,7 @@ struct intel_context {
> > >   #define CONTEXT_GUC_INIT        10
> > >   #define CONTEXT_PERMA_PIN        11
> > >   #define CONTEXT_IS_PARKING        12
> > > +#define CONTEXT_EXITING            13
> > >       struct {
> > >           u64 timeout_us;
> > > diff --git a/drivers/gpu/drm/i915/gt/intel_execlists_submission.c 
> > > b/drivers/gpu/drm/i915/gt/intel_execlists_submission.c
> > > index a4510b5c0c3d..ad72e2c5c4e7 100644
> > > --- a/drivers/gpu/drm/i915/gt/intel_execlists_submission.c
> > > +++ b/drivers/gpu/drm/i915/gt/intel_execlists_submission.c
> > > @@ -480,9 +480,9 @@ __execlists_schedule_in(struct i915_request *rq)
> > >       if (unlikely(intel_context_is_closed(ce) &&
> > >                !intel_engine_has_heartbeat(engine)))
> > > -        intel_context_set_banned(ce);
> > > +        intel_context_set_exiting(ce);
> > > -    if (unlikely(intel_context_is_banned(ce) || bad_request(rq)))
> > > +    if (unlikely(!intel_context_is_schedulable(ce) || bad_request(rq)))
> > >           reset_active(rq, engine);
> > >       if (IS_ENABLED(CONFIG_DRM_I915_DEBUG_GEM))
> > > @@ -1243,7 +1243,7 @@ static unsigned long 
> > > active_preempt_timeout(struct intel_engine_cs *engine,
> > >       /* Force a fast reset for terminated contexts (ignoring sysfs!) */
> > >       if (unlikely(intel_context_is_banned(rq->context) || 
> > > bad_request(rq)))
> > > -        return 1;
> > > +        return INTEL_CONTEXT_BANNED_PREEMPT_TIMEOUT_MS;
> > >       return READ_ONCE(engine->props.preempt_timeout_ms);
> > >   }
> > > diff --git a/drivers/gpu/drm/i915/gt/intel_ring_submission.c 
> > > b/drivers/gpu/drm/i915/gt/intel_ring_submission.c
> > > index f8f279a195c0..d5d6f1fadcae 100644
> > > --- a/drivers/gpu/drm/i915/gt/intel_ring_submission.c
> > > +++ b/drivers/gpu/drm/i915/gt/intel_ring_submission.c
> > > @@ -598,8 +598,9 @@ static void ring_context_reset(struct 
> > > intel_context *ce)
> > >       clear_bit(CONTEXT_VALID_BIT, &ce->flags);
> > >   }
> > > -static void ring_context_ban(struct intel_context *ce,
> > > -                 struct i915_request *rq)
> > > +static void ring_context_revoke(struct intel_context *ce,
> > > +                struct i915_request *rq,
> > > +                unsigned int preempt_timeout_ms)
> > >   {
> > >       struct intel_engine_cs *engine;
> > > @@ -634,7 +635,7 @@ static const struct intel_context_ops 
> > > ring_context_ops = {
> > >       .cancel_request = ring_context_cancel_request,
> > > -    .ban = ring_context_ban,
> > > +    .revoke = ring_context_revoke,
> > >       .pre_pin = ring_context_pre_pin,
> > >       .pin = ring_context_pin,
> > > 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 5a1dfacf24ea..e62ea35513ea 100644
> > > --- a/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
> > > +++ b/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
> > > @@ -2790,7 +2790,9 @@ static void 
> > > __guc_context_set_preemption_timeout(struct intel_guc *guc,
> > >       __guc_context_set_context_policies(guc, &policy, true);
> > >   }
> > > -static void guc_context_ban(struct intel_context *ce, struct 
> > > i915_request *rq)
> > > +static void
> > > +guc_context_revoke(struct intel_context *ce, struct i915_request *rq,
> > > +           unsigned int preempt_timeout_ms)
> > >   {
> > >       struct intel_guc *guc = ce_to_guc(ce);
> > >       struct intel_runtime_pm *runtime_pm =
> > > @@ -2829,7 +2831,8 @@ static void guc_context_ban(struct 
> > > intel_context *ce, struct i915_request *rq)
> > >            * gets kicked off the HW ASAP.
> > >            */
> > >           with_intel_runtime_pm(runtime_pm, wakeref) {
> > > -            __guc_context_set_preemption_timeout(guc, guc_id, 1);
> > > +            __guc_context_set_preemption_timeout(guc, guc_id,
> > > +                                 preempt_timeout_ms);
> > >               __guc_context_sched_disable(guc, ce, guc_id);
> > >           }
> > >       } else {
> > > @@ -2837,7 +2840,7 @@ static void guc_context_ban(struct 
> > > intel_context *ce, struct i915_request *rq)
> > >               with_intel_runtime_pm(runtime_pm, wakeref)
> > >                   __guc_context_set_preemption_timeout(guc,
> > >                                        ce->guc_id.id,
> > > -                                     1);
> > > +                                     preempt_timeout_ms);
> > >           spin_unlock_irqrestore(&ce->guc_state.lock, flags);
> > >       }
> > >   }
> > > @@ -3190,7 +3193,7 @@ static const struct intel_context_ops 
> > > guc_context_ops = {
> > >       .unpin = guc_context_unpin,
> > >       .post_unpin = guc_context_post_unpin,
> > > -    .ban = guc_context_ban,
> > > +    .revoke = guc_context_revoke,
> > >       .cancel_request = guc_context_cancel_request,
> > > @@ -3439,7 +3442,7 @@ static const struct intel_context_ops 
> > > virtual_guc_context_ops = {
> > >       .unpin = guc_virtual_context_unpin,
> > >       .post_unpin = guc_context_post_unpin,
> > > -    .ban = guc_context_ban,
> > > +    .revoke = guc_context_revoke,
> > >       .cancel_request = guc_context_cancel_request,
> > > @@ -3528,7 +3531,7 @@ static const struct intel_context_ops 
> > > virtual_parent_context_ops = {
> > >       .unpin = guc_parent_context_unpin,
> > >       .post_unpin = guc_context_post_unpin,
> > > -    .ban = guc_context_ban,
> > > +    .revoke = guc_context_revoke,
> > >       .cancel_request = guc_context_cancel_request,
> > > diff --git a/drivers/gpu/drm/i915/i915_request.c 
> > > b/drivers/gpu/drm/i915/i915_request.c
> > > index 73d5195146b0..c3937640b119 100644
> > > --- a/drivers/gpu/drm/i915/i915_request.c
> > > +++ b/drivers/gpu/drm/i915/i915_request.c
> > > @@ -611,7 +611,7 @@ bool __i915_request_submit(struct i915_request 
> > > *request)
> > >           goto active;
> > >       }
> > > -    if (unlikely(intel_context_is_banned(request->context)))
> > > +    if (unlikely(!intel_context_is_schedulable(request->context)))
> > >           i915_request_set_error_once(request, -EIO);
> > >       if (unlikely(fatal_error(request->fence.error)))