In the debate as to whether the second read of active->request is
ordered after the dependent reads of the first read of active->request,
just give in and throw a smp_rmb() in there so that ordering of loads is
assured.
Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Cc: Daniel Vetter <daniel.vetter@xxxxxxxx>
---
drivers/gpu/drm/i915/i915_gem.c | 9 +++++----
1 file changed, 5 insertions(+), 4 deletions(-)
diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 28c34cd7f489..c6d85ae35ba6 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -3709,7 +3709,7 @@ i915_gem_object_ggtt_pin(struct drm_i915_gem_object *obj,
return vma;
}
-static __always_inline unsigned __busy_read_flag(unsigned int id)
+static __always_inline unsigned int __busy_read_flag(unsigned int id)
{
/* Note that we could alias engines in the execbuf API, but
* that would be very unwise as it prevents userspace from
@@ -3727,7 +3727,7 @@ static __always_inline unsigned int __busy_write_id(unsigned int id)
return id;
}
-static __always_inline unsigned
+static __always_inline unsigned int
__busy_set_if_active(const struct i915_gem_active *active,
unsigned int (*flag)(unsigned int id))
{
@@ -3745,18 +3745,19 @@ __busy_set_if_active(const struct i915_gem_active *active,
id = request->engine->exec_id;
/* Check that the pointer wasn't reassigned and overwritten. */
+ smp_rmb();
if (request == rcu_access_pointer(active->request))
return flag(id);
} while (1);
}
-static inline unsigned
+static __always_inline unsigned int
busy_check_reader(const struct i915_gem_active *active)
{
return __busy_set_if_active(active, __busy_read_flag);
}
-static inline unsigned
+static __always_inline unsigned int
busy_check_writer(const struct i915_gem_active *active)
{
return __busy_set_if_active(active, __busy_write_id);
--
2.8.1
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