drm/i915: Use EAGAIN for trylock failures

While not good behaviour, it is, however, established behaviour that we
can punt EAGAIN to userspace if we need to retry the ioctl. When trying
to acquire a mutex, prefer to use EAGAIN to propagate losing the race
so that if it does end up back in userspace, we try again.

Fixes: c81471f5e95c ("drm/i915: Copy across scheduler behaviour flags across submit fences")
Closes: https://gitlab.freedesktop.org/drm/intel/issues/800
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20191213160347.1789004-1-chris@chris-wilson.co.uk

diff --git a/drivers/gpu/drm/i915/gt/intel_timeline.c b/drivers/gpu/drm/i915/gt/intel_timeline.c
index 038e05a6336c829ec796065938a1bb791a42c27e..d71aafb66d6ef451faaf45542f907e2a5b3db0e9 100644 (file)
--- a/drivers/gpu/drm/i915/gt/intel_timeline.c
+++ b/drivers/gpu/drm/i915/gt/intel_timeline.c
@@ -527,7 +527,7 @@ int intel_timeline_read_hwsp(struct i915_request *from,
 
        GEM_BUG_ON(rcu_access_pointer(to->timeline) == tl);
 
-       err = -EBUSY;
+       err = -EAGAIN;
        if (mutex_trylock(&tl->mutex)) {
                struct intel_timeline_cacheline *cl = from->hwsp_cacheline;
 

diff --git a/drivers/gpu/drm/i915/i915_request.c b/drivers/gpu/drm/i915/i915_request.c
index c6d59d263550612aa04629639912a3e35a767c03..af2f78e040d72271f150da73639ea934911f3db0 100644 (file)
--- a/drivers/gpu/drm/i915/i915_request.c
+++ b/drivers/gpu/drm/i915/i915_request.c
@@ -771,7 +771,7 @@ i915_request_await_start(struct i915_request *rq, struct i915_request *signal)
        if (!tl) /* already started or maybe even completed */
                return 0;
 
-       fence = ERR_PTR(-EBUSY);
+       fence = ERR_PTR(-EAGAIN);
        if (mutex_trylock(&tl->mutex)) {
                fence = NULL;
                if (!i915_request_started(signal) &&