drm/amdkfd: Use ordered workqueue to restore processes

Restoring multiple processes concurrently can lead to live-locks
where each process prevents the other from validating all its BOs.

v2: fix duplicate check of same variable

Signed-off-by: Felix Kuehling <Felix.Kuehling@amd.com>
Reviewed-by: Oded Gabbay <oded.gabbay@gmail.com>
Signed-off-by: Oded Gabbay <oded.gabbay@gmail.com>

3 files changed, 32 insertions, 6 deletions

diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_module.c b/drivers/gpu/drm/amd/amdkfd/kfd_module.c
index b0acb0603883..e0c07d24d251 100644
--- a/drivers/gpu/drm/amd/amdkfd/kfd_module.c
+++ b/drivers/gpu/drm/amd/amdkfd/kfd_module.c
@@ -133,7 +133,9 @@ static int __init kfd_module_init(void)
         if (err < 0)
                 goto err_topology;
 
-        kfd_process_create_wq();
+        err = kfd_process_create_wq();
+        if (err < 0)
+                goto err_create_wq;
 
         kfd_debugfs_init();
 
@@ -143,6 +145,8 @@ static int __init kfd_module_init(void)
 
         return 0;
 
+err_create_wq:
+        kfd_topology_shutdown();
 err_topology:
         kfd_chardev_exit();
 err_ioctl:
diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_priv.h b/drivers/gpu/drm/amd/amdkfd/kfd_priv.h
index db27f9f13696..96a9cc0f02c9 100644
--- a/drivers/gpu/drm/amd/amdkfd/kfd_priv.h
+++ b/drivers/gpu/drm/amd/amdkfd/kfd_priv.h
@@ -674,7 +674,7 @@ struct amdkfd_ioctl_desc {
         const char *name;
 };
 
-void kfd_process_create_wq(void);
+int kfd_process_create_wq(void);
 void kfd_process_destroy_wq(void);
 struct kfd_process *kfd_create_process(struct file *filep);
 struct kfd_process *kfd_get_process(const struct task_struct *);
diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_process.c b/drivers/gpu/drm/amd/amdkfd/kfd_process.c
index 45ef2d03a975..1711ad0642f7 100644
--- a/drivers/gpu/drm/amd/amdkfd/kfd_process.c
+++ b/drivers/gpu/drm/amd/amdkfd/kfd_process.c
@@ -48,8 +48,17 @@ static DEFINE_MUTEX(kfd_processes_mutex);
 
 DEFINE_SRCU(kfd_processes_srcu);
 
+/* For process termination handling */
 static struct workqueue_struct *kfd_process_wq;
 
+/* Ordered, single-threaded workqueue for restoring evicted
+ * processes. Restoring multiple processes concurrently under memory
+ * pressure can lead to processes blocking each other from validating
+ * their BOs and result in a live-lock situation where processes
+ * remain evicted indefinitely.
+ */
+static struct workqueue_struct *kfd_restore_wq;
+
 static struct kfd_process *find_process(const struct task_struct *thread);
 static void kfd_process_ref_release(struct kref *ref);
 static struct kfd_process *create_process(const struct task_struct *thread,
@@ -59,10 +68,19 @@ static void evict_process_worker(struct work_struct *work);
 static void restore_process_worker(struct work_struct *work);
 
 
-void kfd_process_create_wq(void)
+int kfd_process_create_wq(void)
 {
         if (!kfd_process_wq)
                 kfd_process_wq = alloc_workqueue("kfd_process_wq", 0, 0);
+        if (!kfd_restore_wq)
+                kfd_restore_wq = alloc_ordered_workqueue("kfd_restore_wq", 0);
+
+        if (!kfd_process_wq || !kfd_restore_wq) {
+                kfd_process_destroy_wq();
+                return -ENOMEM;
+        }
+
+        return 0;
 }
 
 void kfd_process_destroy_wq(void)
@@ -71,6 +89,10 @@ void kfd_process_destroy_wq(void)
                 destroy_workqueue(kfd_process_wq);
                 kfd_process_wq = NULL;
         }
+        if (kfd_restore_wq) {
+                destroy_workqueue(kfd_restore_wq);
+                kfd_restore_wq = NULL;
+        }
 }
 
 static void kfd_process_free_gpuvm(struct kgd_mem *mem,
@@ -869,7 +891,7 @@ static void evict_process_worker(struct work_struct *work)
                 dma_fence_signal(p->ef);
                 dma_fence_put(p->ef);
                 p->ef = NULL;
-                schedule_delayed_work(&p->restore_work,
+                queue_delayed_work(kfd_restore_wq, &p->restore_work,
                                 msecs_to_jiffies(PROCESS_RESTORE_TIME_MS));
 
                 pr_debug("Finished evicting pasid %d\n", p->pasid);
@@ -918,7 +940,7 @@ static void restore_process_worker(struct work_struct *work)
         if (ret) {
                 pr_debug("Failed to restore BOs of pasid %d, retry after %d ms\n",
                          p->pasid, PROCESS_BACK_OFF_TIME_MS);
-                ret = schedule_delayed_work(&p->restore_work,
+                ret = queue_delayed_work(kfd_restore_wq, &p->restore_work,
                                 msecs_to_jiffies(PROCESS_BACK_OFF_TIME_MS));
                 WARN(!ret, "reschedule restore work failed\n");
                 return;
@@ -957,7 +979,7 @@ int kfd_resume_all_processes(void)
         int ret = 0, idx = srcu_read_lock(&kfd_processes_srcu);
 
         hash_for_each_rcu(kfd_processes_table, temp, p, kfd_processes) {
-                if (!schedule_delayed_work(&p->restore_work, 0)) {
+                if (!queue_delayed_work(kfd_restore_wq, &p->restore_work, 0)) {
                         pr_err("Restore process %d failed during resume\n",
                                p->pasid);
                         ret = -EFAULT;