On 05/02/2020 12:13, Chris Wilson wrote:
If we have a set of active engines marked as being non-persistent, we
lose track of those if the user replaces those engines with
I915_CONTEXT_PARAM_ENGINES. As part of our uABI contract is that
non-persistent requests are terminated if they are no longer being
tracked by the user's context (in order to prevent a lost request
causing an untracked and so unstoppable GPU hang), we need to apply the
same context cancellation upon changing engines.
Fixes: a0e047156cde ("drm/i915/gem: Make context persistence optional")
Testcase: XXX
Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Cc: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
---
drivers/gpu/drm/i915/gem/i915_gem_context.c | 7 +++++++
1 file changed, 7 insertions(+)
diff --git a/drivers/gpu/drm/i915/gem/i915_gem_context.c b/drivers/gpu/drm/i915/gem/i915_gem_context.c
index 52a749691a8d..20f1d3e0221f 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_context.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_context.c
@@ -1624,11 +1624,18 @@ set_engines(struct i915_gem_context *ctx,
replace:
mutex_lock(&ctx->engines_mutex);
+
+ /* Flush stale requests off the old engines if required */
+ if (!i915_gem_context_is_persistent(ctx) ||
+ !i915_modparams.enable_hangcheck)
+ kill_context(ctx);
Is the negative effect of this is legit contexts can't keep submitting
and changing the map? Only if PREEMPT_TIMEOUT is disabled I think but
still. Might break legitimate userspace. Not that I offer solutions.. :(
Banning changing engines once context went non-persistent? That too can
break someone.
Regards,
Tvrtko
+
if (args->size)
i915_gem_context_set_user_engines(ctx);
else
i915_gem_context_clear_user_engines(ctx);
set.engines = rcu_replace_pointer(ctx->engines, set.engines, 1);
+
mutex_unlock(&ctx->engines_mutex);
call_rcu(&set.engines->rcu, free_engines_rcu);
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