[PATCH 10/12] amdkfd: use schedule() in sync_with_hw

[Oded Gabbay]

amdkfd uses cpu_relax() in its sync_with_hw() function. Because cpu_relax() is
defined as 'REP; NOP' on x86_64, it will block the CPU from servicing
IOMMU PPR requests.

This may cause a deadlock, because sync_with_hw() won't be completed
until the PPR request has been served.

Therefore, we need to use schedule() instead of cpu_relax() as it is the
minimum requirement to allow other threads to execute.

Signed-off-by: Oded Gabbay <oded.gabbay at amd.com>
---
 drivers/gpu/drm/amd/amdkfd/kfd_kernel_queue.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_kernel_queue.c 
b/drivers/gpu/drm/amd/amdkfd/kfd_kernel_queue.c
index 5055fc9..9abac48 100644
--- a/drivers/gpu/drm/amd/amdkfd/kfd_kernel_queue.c
+++ b/drivers/gpu/drm/amd/amdkfd/kfd_kernel_queue.c
@@ -25,6 +25,7 @@
 #include <linux/mutex.h>
 #include <linux/slab.h>
 #include <linux/printk.h>
+#include <linux/sched.h>
 #include "kfd_kernel_queue.h"
 #include "kfd_priv.h"
 #include "kfd_device_queue_manager.h"
@@ -274,7 +275,7 @@ static int sync_with_hw(struct kernel_queue *kq, unsigned 
long timeout_ms)
                                *kq->wptr_kernel, *kq->rptr_kernel);
                        return -ETIME;
                }
-               cpu_relax();
+               schedule();
        }

        return 0;
-- 
2.1.0