Re: [PATCH 16/18] drm/i915: make i915_gem_mmap_ioctl wait for mmap_sem killable

From: Vlastimil Babka
Date: Fri Mar 11 2016 - 10:23:28 EST

On 02/29/2016 02:26 PM, Michal Hocko wrote:
From: Michal Hocko <mhocko@xxxxxxxx>

i915_gem_mmap_ioctl relies on mmap_sem for write. If the waiting
task gets killed by the oom killer it would block oom_reaper from
asynchronous address space reclaim and reduce the chances of timely OOM
resolving. Wait for the lock in the killable mode and return with EINTR
if the task got killed while waiting.

Cc: Daniel Vetter <daniel.vetter@xxxxxxxxx>
Cc: David Airlie <airlied@xxxxxxxx>
Signed-off-by: Michal Hocko <mhocko@xxxxxxxx>

Acked-by: Vlastimil Babka <vbabka@xxxxxxx>

drivers/gpu/drm/i915/i915_gem.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index f68f34606f2f..a50136cbd332 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -1754,7 +1754,10 @@ i915_gem_mmap_ioctl(struct drm_device *dev, void *data,
struct mm_struct *mm = current->mm;
struct vm_area_struct *vma;

- down_write(&mm->mmap_sem);
+ if (down_write_killable(&mm->mmap_sem)) {
+ drm_gem_object_unreference_unlocked(obj);
+ return -EINTR;
+ }
vma = find_vma(mm, addr);
if (vma)
vma->vm_page_prot =