[Intel-gfx] [PATCH] drm/i915: Serialize insertion into the file->mm.request_list

[Chris Wilson]

Currently, we remove the from per-file request list for throttling and
retirement under a dedicated spinlock, but insertion is governed by
struct_mutex. This needs to be the same lock so that the
retirement/insertion of neighbouring requests (at the tail) doesn't
break the list.

Signed-off-by: Chris Wilson <ch...@chris-wilson.co.uk>
Cc: Matthew Auld <matthew.a...@intel.com>
---
 drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c | 9 +++++++--
 drivers/gpu/drm/i915/i915_request.c            | 6 +++---
 2 files changed, 10 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c 
b/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
index 53752006d307..f30258eebbd2 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
@@ -2003,8 +2003,13 @@ static struct i915_vma *eb_parse(struct i915_execbuffer 
*eb, bool is_master)
 static void
 add_to_client(struct i915_request *rq, struct drm_file *file)
 {
-       rq->file_priv = file->driver_priv;
-       list_add_tail(&rq->client_link, &rq->file_priv->mm.request_list);
+       struct drm_i915_file_private *file_priv = file->driver_priv;
+
+       rq->file_priv = file_priv;
+
+       spin_lock(&file_priv->mm.lock);
+       list_add_tail(&rq->client_link, &file_priv->mm.request_list);
+       spin_unlock(&file_priv->mm.lock);
 }
 
 static int eb_submit(struct i915_execbuffer *eb)
diff --git a/drivers/gpu/drm/i915/i915_request.c 
b/drivers/gpu/drm/i915/i915_request.c
index 86c8dd44216b..f1a0a57fc6fc 100644
--- a/drivers/gpu/drm/i915/i915_request.c
+++ b/drivers/gpu/drm/i915/i915_request.c
@@ -165,11 +165,11 @@ static void __notify_execute_cb(struct i915_request *rq)
 }
 
 static inline void
-i915_request_remove_from_client(struct i915_request *request)
+remove_from_client(struct i915_request *request)
 {
        struct drm_i915_file_private *file_priv;
 
-       file_priv = request->file_priv;
+       file_priv = READ_ONCE(request->file_priv);
        if (!file_priv)
                return;
 
@@ -282,7 +282,7 @@ static bool i915_request_retire(struct i915_request *rq)
 
        local_irq_enable();
 
-       i915_request_remove_from_client(rq);
+       remove_from_client(rq);
        list_del(&rq->link);
 
        intel_context_exit(rq->hw_context);
-- 
2.23.0.rc1

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