[PATCH 5/5] drm/amdkfd: Fix a concurrency issue during kfd recovery

[Oak Zeng]

start_cpsch and stop_cpsch can be called during kfd device
initialization or during gpu reset/recovery. So they can
run concurrently. Currently in start_cpsch and stop_cpsch,
pm_init and pm_uninit is not protected by the dpm lock.
Imagine such a case that user use packet manager's function
to submit a pm4 packet to hang hws (ie through command
cat /sys/class/kfd/kfd/topology/nodes/1/gpu_id | sudo tee
/sys/kernel/debug/kfd/hang_hws), while kfd device is under
device reset/recovery so packet manager can be not initialized.
There will be unpredictable protection fault in such case.

This patch moves pm_init/uninit inside the dpm lock and check
packet manager is initialized before using packet manager
function.

Signed-off-by: Oak Zeng <Oak.Zeng at amd.com>
---
 drivers/gpu/drm/amd/amdkfd/kfd_device.c               |  8 +-------
 drivers/gpu/drm/amd/amdkfd/kfd_device_queue_manager.c | 10 ++++++++--
 drivers/gpu/drm/amd/amdkfd/kfd_packet_manager.c       |  3 +++
 3 files changed, 12 insertions(+), 9 deletions(-)

diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_device.c b/drivers/gpu/drm/amd/amdkfd/kfd_device.c
index c51402b..adc2342 100644
--- a/drivers/gpu/drm/amd/amdkfd/kfd_device.c
+++ b/drivers/gpu/drm/amd/amdkfd/kfd_device.c
@@ -1383,18 +1383,12 @@ void kgd2kfd_smi_event_throttle(struct kfd_dev *kfd, uint32_t throttle_bitmask)
  */
 int kfd_debugfs_hang_hws(struct kfd_dev *dev)
 {
-	int r = 0;
-
 	if (dev->dqm->sched_policy != KFD_SCHED_POLICY_HWS) {
 		pr_err("HWS is not enabled");
 		return -EINVAL;
 	}
 
-	r = pm_debugfs_hang_hws(&dev->dqm->dpm);
-	if (!r)
-		r = dqm_debugfs_execute_queues(dev->dqm);
-
-	return r;
+	return dqm_debugfs_execute_queues(dev->dqm);
 }
 
 #endif
diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_device_queue_manager.c b/drivers/gpu/drm/amd/amdkfd/kfd_device_queue_manager.c
index f2984d3..44136d2 100644
--- a/drivers/gpu/drm/amd/amdkfd/kfd_device_queue_manager.c
+++ b/drivers/gpu/drm/amd/amdkfd/kfd_device_queue_manager.c
@@ -1164,6 +1164,7 @@ static int start_cpsch(struct device_queue_manager *dqm)
 
 	retval = 0;
 
+	dqm_lock(dqm);
 	retval = pm_init(&dqm->dpm, dqm);
 	if (retval)
 		goto fail_packet_manager_init;
@@ -1186,7 +1187,6 @@ static int start_cpsch(struct device_queue_manager *dqm)
 
 	init_interrupts(dqm);
 
-	dqm_lock(dqm);
 	/* clear hang status when driver try to start the hw scheduler */
 	dqm->is_hws_hang = false;
 	dqm->is_resetting = false;
@@ -1199,6 +1199,7 @@ static int start_cpsch(struct device_queue_manager *dqm)
 fail_set_sched_resources:
 	pm_uninit(&dqm->dpm, false);
 fail_packet_manager_init:
+	dqm_unlock(dqm);
 	return retval;
 }
 
@@ -1211,12 +1212,12 @@ static int stop_cpsch(struct device_queue_manager *dqm)
 		unmap_queues_cpsch(dqm, KFD_UNMAP_QUEUES_FILTER_ALL_QUEUES, 0);
 	hanging = dqm->is_hws_hang || dqm->is_resetting;
 	dqm->sched_running = false;
-	dqm_unlock(dqm);
 
 	pm_release_ib(&dqm->dpm);
 
 	kfd_gtt_sa_free(dqm->dev, dqm->fence_mem);
 	pm_uninit(&dqm->dpm, hanging);
+	dqm_unlock(dqm);
 
 	return 0;
 }
@@ -2104,6 +2105,11 @@ int dqm_debugfs_execute_queues(struct device_queue_manager *dqm)
 	int r = 0;
 
 	dqm_lock(dqm);
+	r = pm_debugfs_hang_hws(&dqm->dpm);
+	if (r) {
+		dqm_unlock(dqm);
+		return r;
+	}
 	dqm->active_runlist = true;
 	r = execute_queues_cpsch(dqm, KFD_UNMAP_QUEUES_FILTER_ALL_QUEUES, 0);
 	dqm_unlock(dqm);
diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_packet_manager.c b/drivers/gpu/drm/amd/amdkfd/kfd_packet_manager.c
index b130cc0..0123e64 100644
--- a/drivers/gpu/drm/amd/amdkfd/kfd_packet_manager.c
+++ b/drivers/gpu/drm/amd/amdkfd/kfd_packet_manager.c
@@ -448,6 +448,9 @@ int pm_debugfs_hang_hws(struct packet_manager *pm)
 	uint32_t *buffer, size;
 	int r = 0;
 
+	if (!pm->priv_queue)
+		return -EBUSY;
+
 	size = pm->pmf->query_status_size;
 	mutex_lock(&pm->lock);
 	kq_acquire_packet_buffer(pm->priv_queue,
-- 
2.7.4