[PATCH 2/3] drm/amdkfd: avoid HMM change cause circular lock dependency v2

Yang, Philip
2019-01-10T17:02:47Z

There is circular lock between gfx and kfd path with HMM change:
lock(dqm) -> bo::reserve -> amdgpu_mn_lock

To avoid this, move init/unint_mqd() out of lock(dqm), to remove nested
locking between mmap_sem and bo::reserve. The locking order
is: bo::reserve -> amdgpu_mn_lock(p->mn)

Change-Id: I2ec09a47571f6b4c8eaef93f22c0a600f5f70153
Signed-off-by: Philip Yang <Philip.Yang@amd.com>
---
.../drm/amd/amdkfd/kfd_device_queue_manager.c | 32 ++++++++++---------
1 file changed, 17 insertions(+), 15 deletions(-)

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 8372556b52eb..efe0d3c0215b 100644
--- a/drivers/gpu/drm/amd/amdkfd/kfd_device_queue_manager.c
+++ b/drivers/gpu/drm/amd/amdkfd/kfd_device_queue_manager.c
@@ -1156,21 +1156,17 @@ static int create_queue_cpsch(struct device_queue_manager *dqm, struct queue *q,
int retval;
struct mqd_manager *mqd_mgr;

- retval = 0;
-
- dqm_lock(dqm);
-
if (dqm->total_queue_count >= max_num_of_queues_per_device) {
pr_warn("Can't create new usermode queue because %d queues were already created\n",
dqm->total_queue_count);
retval = -EPERM;
- goto out_unlock;
+ goto out;
}

if (q->properties.type == KFD_QUEUE_TYPE_SDMA) {
retval = allocate_sdma_queue(dqm, &q->sdma_id);
if (retval)
- goto out_unlock;
+ goto out;
q->properties.sdma_queue_id =
q->sdma_id / get_num_sdma_engines(dqm);
q->properties.sdma_engine_id =
@@ -1181,6 +1177,9 @@ static int create_queue_cpsch(struct device_queue_manager *dqm, struct queue *q,
if (retval)
goto out_deallocate_sdma_queue;

+ /* Do init_mqd before dqm_lock(dqm) to avoid circular locking order:
+ * lock(dqm) -> bo::reserve
+ */
mqd_mgr = dqm->ops.get_mqd_manager(dqm,
get_mqd_type_from_queue_type(q->properties.type));

@@ -1188,6 +1187,7 @@ static int create_queue_cpsch(struct device_queue_manager *dqm, struct queue *q,
retval = -ENOMEM;
goto out_deallocate_doorbell;
}
+
/*
* Eviction state logic: we only mark active queues as evicted
* to avoid the overhead of restoring inactive queues later
@@ -1196,9 +1196,7 @@ static int create_queue_cpsch(struct device_queue_manager *dqm, struct queue *q,
q->properties.is_evicted = (q->properties.queue_size > 0 &&
q->properties.queue_percent > 0 &&
q->properties.queue_address != 0);
-
dqm->asic_ops.init_sdma_vm(dqm, q, qpd);
-
q->properties.tba_addr = qpd->tba_addr;
q->properties.tma_addr = qpd->tma_addr;
retval = mqd_mgr->init_mqd(mqd_mgr, &q->mqd, &q->mqd_mem_obj,
@@ -1206,6 +1204,8 @@ static int create_queue_cpsch(struct device_queue_manager *dqm, struct queue *q,
if (retval)
goto out_deallocate_doorbell;

+ dqm_lock(dqm);
+
list_add(&q->list, &qpd->queues_list);
qpd->queue_count++;
if (q->properties.is_active) {
@@ -1233,9 +1233,7 @@ static int create_queue_cpsch(struct device_queue_manager *dqm, struct queue *q,
out_deallocate_sdma_queue:
if (q->properties.type == KFD_QUEUE_TYPE_SDMA)
deallocate_sdma_queue(dqm, q->sdma_id);
-out_unlock:
- dqm_unlock(dqm);
-
+out:
return retval;
}

@@ -1398,8 +1396,6 @@ static int destroy_queue_cpsch(struct device_queue_manager *dqm,
qpd->reset_wavefronts = true;
}

- mqd_mgr->uninit_mqd(mqd_mgr, q->mqd, q->mqd_mem_obj);
-
/*
* Unconditionally decrement this counter, regardless of the queue's
* type
@@ -1410,6 +1406,9 @@ static int destroy_queue_cpsch(struct device_queue_manager *dqm,

dqm_unlock(dqm);

+ /* Do uninit_mqd after dqm_unlock(dqm) to avoid circular locking */
+ mqd_mgr->uninit_mqd(mqd_mgr, q->mqd, q->mqd_mem_obj);
+
return retval;

failed:
@@ -1631,7 +1630,11 @@ static int process_termination_cpsch(struct device_queue_manager *dqm,
qpd->reset_wavefronts = false;
}

- /* lastly, free mqd resources */
+ dqm_unlock(dqm);
+
+ /* Lastly, free mqd resources.
+ * Do uninit_mqd() after dqm_unlock to avoid circular locking.
+ */
list_for_each_entry_safe(q, next, &qpd->queues_list, list) {
mqd_mgr = dqm->ops.get_mqd_manager(dqm,
get_mqd_type_from_queue_type(q->properties.type));
@@ -1645,7 +1648,6 @@ static int process_termination_cpsch(struct device_queue_manager *dqm,
}

out:
- dqm_unlock(dqm);
return retval;
}

--
2.17.1