path: root/meta-amd-bsp/recipes-kernel/linux/linux-yocto-4.14.71/1164-drm-amdkfd-Use-ref-count-to-prevent-kfd_process-dest.patch

From a3e6779469a3bb88b61226d87eb7055651a4a687 Mon Sep 17 00:00:00 2001
From: Felix Kuehling <Felix.Kuehling@amd.com>
Date: Tue, 26 Jul 2016 17:41:11 -0400
Subject: [PATCH 1164/4131] drm/amdkfd: Use ref count to prevent kfd_process
 destruction

Use a reference counter instead of a lock to prevent process
destruction while functions running out of process context are using
the kfd_process structure. In many cases these functions don't need
the structure to be locked. In the few cases that really do need the
process lock, take it explicitly.

This helps simplify lock dependencies between the process lock and
other locks.

Change-Id: Ie8191f5a9f503b576d8f1eed5f2b14eca804d6ac
Signed-off-by: Felix Kuehling <Felix.Kuehling@amd.com>
---
 drivers/gpu/drm/amd/amdkfd/kfd_device.c            | 10 +++++----
 .../gpu/drm/amd/amdkfd/kfd_device_queue_manager.c  |  2 +-
 drivers/gpu/drm/amd/amdkfd/kfd_events.c            | 19 ++++++++--------
 drivers/gpu/drm/amd/amdkfd/kfd_priv.h              |  1 +
 drivers/gpu/drm/amd/amdkfd/kfd_process.c           | 26 +++++++++++++++-------
 drivers/gpu/drm/amd/amdkfd/kfd_rdma.c              |  6 +++--
 6 files changed, 40 insertions(+), 24 deletions(-)

diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_device.c b/drivers/gpu/drm/amd/amdkfd/kfd_device.c
index 0111510..6ac3ec6 100644
--- a/drivers/gpu/drm/amd/amdkfd/kfd_device.c
+++ b/drivers/gpu/drm/amd/amdkfd/kfd_device.c
@@ -675,7 +675,8 @@ int kgd2kfd_quiesce_mm(struct kfd_dev *kfd, struct mm_struct *mm)
 
 	/* Because we are called from arbitrary context (workqueue) as opposed
 	 * to process context, kfd_process could attempt to exit while we are
-	 * running so the lookup function returns a read-locked process. */
+	 * running so the lookup function increments the process ref count.
+	 */
 	p = kfd_lookup_process_by_mm(mm);
 	if (!p)
 		return -ENODEV;
@@ -685,7 +686,7 @@ int kgd2kfd_quiesce_mm(struct kfd_dev *kfd, struct mm_struct *mm)
 	if (pdd)
 		r = process_evict_queues(kfd->dqm, &pdd->qpd);
 
-	up_read(&p->lock);
+	kfd_unref_process(p);
 	return r;
 }
 
@@ -701,7 +702,8 @@ int kgd2kfd_resume_mm(struct kfd_dev *kfd, struct mm_struct *mm)
 
 	/* Because we are called from arbitrary context (workqueue) as opposed
 	 * to process context, kfd_process could attempt to exit while we are
-	 * running so the lookup function returns a read-locked process. */
+	 * running so the lookup function increments the process ref count.
+	 */
 	p = kfd_lookup_process_by_mm(mm);
 	if (!p)
 		return -ENODEV;
@@ -718,7 +720,7 @@ int kgd2kfd_resume_mm(struct kfd_dev *kfd, struct mm_struct *mm)
 			up_read(&mm->mmap_sem);
 	}
 
-	up_read(&p->lock);
+	kfd_unref_process(p);
 	return r;
 }
 
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 df9b3f3..5f1fbbe 100644
--- a/drivers/gpu/drm/amd/amdkfd/kfd_device_queue_manager.c
+++ b/drivers/gpu/drm/amd/amdkfd/kfd_device_queue_manager.c
@@ -1581,7 +1581,7 @@ int kfd_process_vm_fault(struct device_queue_manager *dqm,
 	pdd = kfd_get_process_device_data(dqm->dev, p);
 	if (pdd)
 		ret = process_evict_queues(dqm, &pdd->qpd);
-	up_read(&p->lock);
+	kfd_unref_process(p);
 
 	return ret;
 }
diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_events.c b/drivers/gpu/drm/amd/amdkfd/kfd_events.c
index 5f7aa78..6a354f3 100644
--- a/drivers/gpu/drm/amd/amdkfd/kfd_events.c
+++ b/drivers/gpu/drm/amd/amdkfd/kfd_events.c
@@ -661,7 +661,8 @@ void kfd_signal_event_interrupt(unsigned int pasid, uint32_t partial_id,
 
 	/* Because we are called from arbitrary context (workqueue) as opposed
 	 * to process context, kfd_process could attempt to exit while we are
-	 * running so the lookup function returns a read-locked process. */
+	 * running so the lookup function increments the process ref count.
+	 */
 	struct kfd_process *p = kfd_lookup_process_by_pasid(pasid);
 	if (!p)
 		return; /* Presumably process exited. */
@@ -691,7 +692,7 @@ void kfd_signal_event_interrupt(unsigned int pasid, uint32_t partial_id,
 	}
 
 	mutex_unlock(&p->event_mutex);
-	up_read(&p->lock);
+	kfd_unref_process(p);
 }
 
 static struct kfd_event_waiter *alloc_event_waiters(uint32_t num_events)
@@ -1024,7 +1025,7 @@ void kfd_signal_iommu_event(struct kfd_dev *dev, unsigned int pasid,
 	/*
 	 * Because we are called from arbitrary context (workqueue) as opposed
 	 * to process context, kfd_process could attempt to exit while we are
-	 * running so the lookup function returns a read-locked process.
+	 * running so the lookup function increments the process ref count.
 	 */
 	struct kfd_process *p = kfd_lookup_process_by_pasid(pasid);
 	struct mm_struct *mm;
@@ -1037,7 +1038,7 @@ void kfd_signal_iommu_event(struct kfd_dev *dev, unsigned int pasid,
 	 */
 	mm = get_task_mm(p->lead_thread);
 	if (!mm) {
-		up_read(&p->lock);
+		kfd_unref_process(p);
 		return; /* Process is exiting */
 	}
 
@@ -1080,7 +1081,8 @@ void kfd_signal_iommu_event(struct kfd_dev *dev, unsigned int pasid,
 			&memory_exception_data);
 
 	mutex_unlock(&p->event_mutex);
-	up_read(&p->lock);
+
+	kfd_unref_process(p);
 }
 
 void kfd_signal_hw_exception_event(unsigned int pasid)
@@ -1088,7 +1090,7 @@ void kfd_signal_hw_exception_event(unsigned int pasid)
 	/*
 	 * Because we are called from arbitrary context (workqueue) as opposed
 	 * to process context, kfd_process could attempt to exit while we are
-	 * running so the lookup function returns a read-locked process.
+	 * running so the lookup function increments the process ref count.
 	 */
 	struct kfd_process *p = kfd_lookup_process_by_pasid(pasid);
 
@@ -1101,7 +1103,7 @@ void kfd_signal_hw_exception_event(unsigned int pasid)
 	lookup_events_by_type_and_signal(p, KFD_EVENT_TYPE_HW_EXCEPTION, NULL);
 
 	mutex_unlock(&p->event_mutex);
-	up_read(&p->lock);
+	kfd_unref_process(p);
 }
 
 void kfd_signal_vm_fault_event(struct kfd_dev *dev, unsigned int pasid,
@@ -1138,7 +1140,6 @@ void kfd_signal_vm_fault_event(struct kfd_dev *dev, unsigned int pasid,
 	}
 
 	mutex_unlock(&p->event_mutex);
-	up_read(&p->lock);
-
+	kfd_unref_process(p);
 }
 
diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_priv.h b/drivers/gpu/drm/amd/amdkfd/kfd_priv.h
index cea4efd..420aa64 100644
--- a/drivers/gpu/drm/amd/amdkfd/kfd_priv.h
+++ b/drivers/gpu/drm/amd/amdkfd/kfd_priv.h
@@ -685,6 +685,7 @@ struct kfd_process *kfd_create_process(struct file *filep);
 struct kfd_process *kfd_get_process(const struct task_struct *);
 struct kfd_process *kfd_lookup_process_by_pasid(unsigned int pasid);
 struct kfd_process *kfd_lookup_process_by_mm(const struct mm_struct *mm);
+void kfd_unref_process(struct kfd_process *p);
 
 struct kfd_process_device *kfd_bind_process_to_device(struct kfd_dev *dev,
 						struct kfd_process *p);
diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_process.c b/drivers/gpu/drm/amd/amdkfd/kfd_process.c
index 889d165..03b701a 100644
--- a/drivers/gpu/drm/amd/amdkfd/kfd_process.c
+++ b/drivers/gpu/drm/amd/amdkfd/kfd_process.c
@@ -56,6 +56,7 @@ static struct workqueue_struct *kfd_process_wq;
 
 static struct kfd_process *find_process(const struct task_struct *thread,
 		bool lock);
+static void kfd_process_ref_release(struct kref *ref);
 static struct kfd_process *create_process(const struct task_struct *thread);
 static int kfd_process_init_cwsr(struct kfd_process *p, struct file *filep);
 
@@ -260,21 +261,26 @@ static struct kfd_process *find_process_by_mm(const struct mm_struct *mm)
 }
 
 static struct kfd_process *find_process(const struct task_struct *thread,
-		bool lock)
+		bool ref)
 {
 	struct kfd_process *p;
 	int idx;
 
 	idx = srcu_read_lock(&kfd_processes_srcu);
 	p = find_process_by_mm(thread->mm);
-	if (p && lock)
-		down_read(&p->lock);
+	if (p && ref)
+		kref_get(&p->ref);
 	srcu_read_unlock(&kfd_processes_srcu, idx);
 
 	return p;
 }
 
-/* This returns with process->lock read-locked. */
+void kfd_unref_process(struct kfd_process *p)
+{
+	kref_put(&p->ref, kfd_process_ref_release);
+}
+
+/* This increments the process->ref counter. */
 struct kfd_process *kfd_lookup_process_by_pid(struct pid *pid)
 {
 	struct task_struct *task = NULL;
@@ -853,6 +859,8 @@ void kfd_process_iommu_unbind_callback(struct kfd_dev *dev, unsigned int pasid)
 
 	mutex_unlock(get_dbgmgr_mutex());
 
+	down_write(&p->lock);
+
 	pdd = kfd_get_process_device_data(dev, p);
 	if (pdd->reset_wavefronts) {
 		dbgdev_wave_reset_wavefronts(pdd->dev, p);
@@ -860,6 +868,8 @@ void kfd_process_iommu_unbind_callback(struct kfd_dev *dev, unsigned int pasid)
 	}
 
 	up_write(&p->lock);
+
+	kfd_unref_process(p);
 }
 
 struct kfd_process_device *kfd_get_first_process_device_data(struct kfd_process *p)
@@ -991,7 +1001,7 @@ void kfd_process_device_remove_obj_handle(struct kfd_process_device *pdd,
 	kfree(buf_obj);
 }
 
-/* This returns with process->lock read-locked. */
+/* This increments the process->ref counter. */
 struct kfd_process *kfd_lookup_process_by_pasid(unsigned int pasid)
 {
 	struct kfd_process *p, *ret_p = NULL;
@@ -1001,7 +1011,7 @@ struct kfd_process *kfd_lookup_process_by_pasid(unsigned int pasid)
 
 	hash_for_each_rcu(kfd_processes_table, temp, p, kfd_processes) {
 		if (p->pasid == pasid) {
-			down_read(&p->lock);
+			kref_get(&p->ref);
 			ret_p = p;
 			break;
 		}
@@ -1012,7 +1022,7 @@ struct kfd_process *kfd_lookup_process_by_pasid(unsigned int pasid)
 	return ret_p;
 }
 
-/* This returns with process->lock read-locked. */
+/* This increments the process->ref counter. */
 struct kfd_process *kfd_lookup_process_by_mm(const struct mm_struct *mm)
 {
 	struct kfd_process *p;
@@ -1021,7 +1031,7 @@ struct kfd_process *kfd_lookup_process_by_mm(const struct mm_struct *mm)
 
 	p = find_process_by_mm(mm);
 	if (p != NULL)
-		down_read(&p->lock);
+		kref_get(&p->ref);
 
 	srcu_read_unlock(&kfd_processes_srcu, idx);
 
diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_rdma.c b/drivers/gpu/drm/amd/amdkfd/kfd_rdma.c
index f58b57e..56bf9a2 100644
--- a/drivers/gpu/drm/amd/amdkfd/kfd_rdma.c
+++ b/drivers/gpu/drm/amd/amdkfd/kfd_rdma.c
@@ -80,6 +80,7 @@ static int get_pages(uint64_t address, uint64_t length, struct pid *pid,
 				__func__);
 		return -EINVAL;
 	}
+	down_read(&p->lock);
 
 	buf_obj = kfd_process_find_bo_from_interval(p, address, last);
 	if (!buf_obj) {
@@ -127,6 +128,7 @@ static int get_pages(uint64_t address, uint64_t length, struct pid *pid,
 	kfree(rdma_cb_data);
 out:
 	up_read(&p->lock);
+	kfd_unref_process(p);
 
 	return ret;
 }
@@ -203,7 +205,7 @@ static int put_pages(struct amd_p2p_info **p_p2p_data)
 	if (!ret)
 		*p_p2p_data = NULL;
 
-	up_read(&p->lock);
+	kfd_unref_process(p);
 
 	return ret;
 }
@@ -232,7 +234,7 @@ static int is_gpu_address(uint64_t address, struct pid *pid)
 
 	buf_obj = kfd_process_find_bo_from_interval(p, address, address);
 
-	up_read(&p->lock);
+	kfd_unref_process(p);
 	if (!buf_obj)
 		return 0;
 	else
-- 
2.7.4