Am 2023-03-13 um 14:35 schrieb David Belanger:
Handle case when module is unloaded (kfd_exit) before a process space
(mm_struct) is released.
v2: Fixed potential race conditions by removing all kfd_process from
the process table first, then working on releasing the resources.
v3: Fixed loop element access / synchronization. Fixed extra empty lines.
Signed-off-by: David Belanger <david.belanger@xxxxxxx>
This looks good. I'd make the comments slightly less verbose. See
inline. With that fixed, the patch is
Reviewed-by: Felix Kuehling <Felix.Kuehling@xxxxxxx>
---
drivers/gpu/drm/amd/amdkfd/kfd_module.c | 1 +
drivers/gpu/drm/amd/amdkfd/kfd_priv.h | 1 +
drivers/gpu/drm/amd/amdkfd/kfd_process.c | 75 +++++++++++++++++++++---
3 files changed, 70 insertions(+), 7 deletions(-)
diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_module.c b/drivers/gpu/drm/amd/amdkfd/kfd_module.c
index 09b966dc3768..aee2212e52f6 100644
--- a/drivers/gpu/drm/amd/amdkfd/kfd_module.c
+++ b/drivers/gpu/drm/amd/amdkfd/kfd_module.c
@@ -77,6 +77,7 @@ static int kfd_init(void)
static void kfd_exit(void)
{
+ kfd_cleanup_processes();
kfd_debugfs_fini();
kfd_process_destroy_wq();
kfd_procfs_shutdown();
diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_priv.h b/drivers/gpu/drm/amd/amdkfd/kfd_priv.h
index bfa30d12406b..7e4d992e48b3 100644
--- a/drivers/gpu/drm/amd/amdkfd/kfd_priv.h
+++ b/drivers/gpu/drm/amd/amdkfd/kfd_priv.h
@@ -928,6 +928,7 @@ bool kfd_dev_is_large_bar(struct kfd_dev *dev);
int kfd_process_create_wq(void);
void kfd_process_destroy_wq(void);
+void kfd_cleanup_processes(void);
struct kfd_process *kfd_create_process(struct file *filep);
struct kfd_process *kfd_get_process(const struct task_struct *task);
struct kfd_process *kfd_lookup_process_by_pasid(u32 pasid);
diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_process.c b/drivers/gpu/drm/amd/amdkfd/kfd_process.c
index ebabe92f7edb..5614ef2ac49e 100644
--- a/drivers/gpu/drm/amd/amdkfd/kfd_process.c
+++ b/drivers/gpu/drm/amd/amdkfd/kfd_process.c
@@ -1167,6 +1167,17 @@ static void kfd_process_free_notifier(struct mmu_notifier *mn)
kfd_unref_process(container_of(mn, struct kfd_process, mmu_notifier));
}
+static void kfd_process_notifier_release_internal(struct kfd_process *p)
+{
+ cancel_delayed_work_sync(&p->eviction_work);
+ cancel_delayed_work_sync(&p->restore_work);
+
+ /* Indicate to other users that MM is no longer valid */
+ p->mm = NULL;
+
+ mmu_notifier_put(&p->mmu_notifier);
+}
+
static void kfd_process_notifier_release(struct mmu_notifier *mn,
struct mm_struct *mm)
{
@@ -1181,17 +1192,22 @@ static void kfd_process_notifier_release(struct mmu_notifier *mn,
return;
mutex_lock(&kfd_processes_mutex);
+ /*
+ * Do early return if table is empty.
+ *
+ * This could potentially happen if this function is called concurrently
+ * by mmu_notifier and by kfd_cleanup_pocesses.
+ *
+ */
+ if (hash_empty(kfd_processes_table)) {
+ mutex_unlock(&kfd_processes_mutex);
+ return;
+ }
hash_del_rcu(&p->kfd_processes);
mutex_unlock(&kfd_processes_mutex);
synchronize_srcu(&kfd_processes_srcu);
- cancel_delayed_work_sync(&p->eviction_work);
- cancel_delayed_work_sync(&p->restore_work);
-
- /* Indicate to other users that MM is no longer valid */
- p->mm = NULL;
-
- mmu_notifier_put(&p->mmu_notifier);
+ kfd_process_notifier_release_internal(p);
}
static const struct mmu_notifier_ops kfd_process_mmu_notifier_ops = {
@@ -1200,6 +1216,51 @@ static const struct mmu_notifier_ops kfd_process_mmu_notifier_ops = {
.free_notifier = kfd_process_free_notifier,
};
+void kfd_cleanup_processes(void)
+{
+ /*
+ * This code handles the case when driver is being unloaded before all
+ * mm_struct are released. We need to safely free the kfd_process and
+ * avoid race conditions with mmu_notifier that might try to free them.
+ *
+ */
Comments describing a function's overall purpose usually go before the
function.
+
+ struct kfd_process *p;
+ struct hlist_node *p_temp;
+ unsigned int temp;
+ HLIST_HEAD(cleanup_list);
+
+ /*
+ * Move all remaining kfd_process from the process table to a
+ * temp list for processing. Once done, callback from mmu_notifier
+ * release will not see the kfd_process in the table and do early return,
+ * avoiding double free issues.
+ */
+ mutex_lock(&kfd_processes_mutex);
+ hash_for_each_safe(kfd_processes_table, temp, p_temp, p, kfd_processes) {
+ hash_del_rcu(&p->kfd_processes);
+ synchronize_srcu(&kfd_processes_srcu);
+ hlist_add_head(&p->kfd_processes, &cleanup_list);
+ }
+ mutex_unlock(&kfd_processes_mutex);
+
+
+ /*
+ * Release resources for all outstanding kfd_process collected.
+ */
This comment is redundant. The processing of the cleanup list is already
explained above.
+ hlist_for_each_entry_safe(p, p_temp, &cleanup_list, kfd_processes)
+ kfd_process_notifier_release_internal(p);
+
+ /*
+ * Must be called after all mmu_notifier_put are done and before
+ * kfd_process_wq is released.
+ *
+ * Ensures that all outstanding free_notifier get called, triggering
+ * the release of the kfd_process struct.
One of these sentences is redundant. I'd keep just the second one.
Regards,
Felix
+ */
+ mmu_notifier_synchronize();
+}
+
static int kfd_process_init_cwsr_apu(struct kfd_process *p, struct file *filep)
{
unsigned long offset;
