drm/xe/multi_queue: Protect priority against concurrent access

Use a spinlock to protect multi-queue priority being concurrently
updated by multiple set_priority ioctls and to protect against
concurrent read and write to this field.

v2: Update documentation, remove WRITE/READ_LOCK() (Thomas)
    Use scoped_guard, reduced lock scope (Matt Brost)
v3: Fix author (checkpatch)

Signed-off-by: Niranjana Vishwanathapura <niranjana.vishwanathapura@intel.com>
Reviewed-by: Matthew Brost <matthew.brost@intel.com>
Reviewed-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Link: https://patch.msgid.link/20260126174241.3470390-2-niranjana.vishwanathapura@intel.com

diff --git a/drivers/gpu/drm/xe/xe_exec_queue.c b/drivers/gpu/drm/xe/xe_exec_queue.c
index 7e7e663189e4af7fe0206f3c493ae5b8443ffdd6..66d0e10ee2c4ac8d15c2eac5ce93c0bf8d82106c 100644 (file)
--- a/drivers/gpu/drm/xe/xe_exec_queue.c
+++ b/drivers/gpu/drm/xe/xe_exec_queue.c
@@ -230,6 +230,7 @@ static struct xe_exec_queue *__xe_exec_queue_alloc(struct xe_device *xe,
        INIT_LIST_HEAD(&q->multi_gt_link);
        INIT_LIST_HEAD(&q->hw_engine_group_link);
        INIT_LIST_HEAD(&q->pxp.link);
+       spin_lock_init(&q->multi_queue.lock);
        q->multi_queue.priority = XE_MULTI_QUEUE_PRIORITY_NORMAL;
 
        q->sched_props.timeslice_us = hwe->eclass->sched_props.timeslice_us;

diff --git a/drivers/gpu/drm/xe/xe_exec_queue_types.h b/drivers/gpu/drm/xe/xe_exec_queue_types.h
index e987d431ce27fb3ddeaed491911e056f42fa2dfa..3791fed34ffa56f515476d183f1f382c30b9d4dc 100644 (file)
--- a/drivers/gpu/drm/xe/xe_exec_queue_types.h
+++ b/drivers/gpu/drm/xe/xe_exec_queue_types.h
@@ -161,8 +161,13 @@ struct xe_exec_queue {
                struct xe_exec_queue_group *group;
                /** @multi_queue.link: Link into group's secondary queues list */
                struct list_head link;
-               /** @multi_queue.priority: Queue priority within the multi-queue group */
+               /**
+                * @multi_queue.priority: Queue priority within the multi-queue group.
+                * It is protected by @multi_queue.lock.
+                */
                enum xe_multi_queue_priority priority;
+               /** @multi_queue.lock: Lock for protecting certain members */
+               spinlock_t lock;
                /** @multi_queue.pos: Position of queue within the multi-queue group */
                u8 pos;
                /** @multi_queue.valid: Queue belongs to a multi queue group */

diff --git a/drivers/gpu/drm/xe/xe_guc_submit.c b/drivers/gpu/drm/xe/xe_guc_submit.c
index 456f549c16f6f186ef6669c4619a02f8c61720cc..1f4625ddae0eaa751529794a2104152fc541af0c 100644 (file)
--- a/drivers/gpu/drm/xe/xe_guc_submit.c
+++ b/drivers/gpu/drm/xe/xe_guc_submit.c
@@ -804,6 +804,7 @@ static void xe_guc_exec_queue_group_cgp_sync(struct xe_guc *guc,
 {
        struct xe_exec_queue_group *group = q->multi_queue.group;
        struct xe_device *xe = guc_to_xe(guc);
+       enum xe_multi_queue_priority priority;
        long ret;
 
        /*
@@ -827,7 +828,10 @@ static void xe_guc_exec_queue_group_cgp_sync(struct xe_guc *guc,
                return;
        }
 
-       xe_lrc_set_multi_queue_priority(q->lrc[0], q->multi_queue.priority);
+       scoped_guard(spinlock, &q->multi_queue.lock)
+               priority = q->multi_queue.priority;
+
+       xe_lrc_set_multi_queue_priority(q->lrc[0], priority);
        xe_guc_exec_queue_group_cgp_update(xe, q);
 
        WRITE_ONCE(group->sync_pending, true);
@@ -2181,15 +2185,22 @@ static int guc_exec_queue_set_multi_queue_priority(struct xe_exec_queue *q,
 
        xe_gt_assert(guc_to_gt(exec_queue_to_guc(q)), xe_exec_queue_is_multi_queue(q));
 
-       if (q->multi_queue.priority == priority ||
-           exec_queue_killed_or_banned_or_wedged(q))
+       if (exec_queue_killed_or_banned_or_wedged(q))
                return 0;
 
        msg = kmalloc(sizeof(*msg), GFP_KERNEL);
        if (!msg)
                return -ENOMEM;
 
-       q->multi_queue.priority = priority;
+       scoped_guard(spinlock, &q->multi_queue.lock) {
+               if (q->multi_queue.priority == priority) {
+                       kfree(msg);
+                       return 0;
+               }
+
+               q->multi_queue.priority = priority;
+       }
+
        guc_exec_queue_add_msg(q, msg, SET_MULTI_QUEUE_PRIORITY);
 
        return 0;