drm/amdkfd: change kfd process kref count at creation

kfd process kref count(process->ref) is initialized to 1 by kref_init. After
it is created not need to increase its kref. Instad add kfd process kref at kfd
process mmu notifier allocation since we already decrease the kref at
free_notifier of mmu_notifier_ops, so pair them.

When user process opens kfd node multiple times the kfd process kref is
increased each time to balance with kfd node close operation.

Signed-off-by: Xiaogang Chen <xiaogang.chen@amd.com>
Reviewed-by: Felix Kuehling <felix.kuehling@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_process.c b/drivers/gpu/drm/amd/amdkfd/kfd_process.c
index ff34bb1..87cd52c 100644 (file)
--- a/drivers/gpu/drm/amd/amdkfd/kfd_process.c
+++ b/drivers/gpu/drm/amd/amdkfd/kfd_process.c
@@ -854,8 +854,10 @@ struct kfd_process *kfd_create_process(struct task_struct *thread)
                goto out;
        }
 
-       /* A prior open of /dev/kfd could have already created the process. */
-       process = find_process(thread, false);
+       /* A prior open of /dev/kfd could have already created the process.
+        * find_process will increase process kref in this case
+        */
+       process = find_process(thread, true);
        if (process) {
                pr_debug("Process already found\n");
        } else {
@@ -903,8 +905,6 @@ struct kfd_process *kfd_create_process(struct task_struct *thread)
                init_waitqueue_head(&process->wait_irq_drain);
        }
 out:
-       if (!IS_ERR(process))
-               kref_get(&process->ref);
        mutex_unlock(&kfd_processes_mutex);
        mmput(thread->mm);
 
@@ -1190,10 +1190,8 @@ static void kfd_process_ref_release(struct kref *ref)
 
 static struct mmu_notifier *kfd_process_alloc_notifier(struct mm_struct *mm)
 {
-       int idx = srcu_read_lock(&kfd_processes_srcu);
-       struct kfd_process *p = find_process_by_mm(mm);
-
-       srcu_read_unlock(&kfd_processes_srcu, idx);
+       /* This increments p->ref counter if kfd process p exists */
+       struct kfd_process *p = kfd_lookup_process_by_mm(mm);
 
        return p ? &p->mmu_notifier : ERR_PTR(-ESRCH);
 }