From f1925f3309d13d431f70e7b6b72ba59cae90fdff Mon Sep 17 00:00:00 2001
From: Chris Wilson <chris@chris-wilson.co.uk>
Date: Fri, 13 Dec 2019 16:03:47 +0000
Subject: [PATCH] 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
---
drivers/gpu/drm/i915/gt/intel_timeline.c | 2 +-
drivers/gpu/drm/i915/i915_request.c | 2 +-
2 files changed, 2 insertions(+), 2 deletions(-)
diff --git a/drivers/gpu/drm/i915/gt/intel_timeline.c b/drivers/gpu/drm/i915/gt/intel_timeline.c
index 038e05a6336c..d71aafb66d6e 100644
--- 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 c6d59d263550..af2f78e040d7 100644
--- 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) &&