If we end up calling the shrinker, which in turn requires the OOM
killer, we may end up infinitely waiting for a process to die if the OOM
chooses. The case that this prevents occurs in execbuf. The forked
variants of gem_evict_everything is a good way to hit it. This is
exacerbated by Daniel's recent patch to give OOM precedence to the GEM
tests.
It's a twisted form of a deadlock.
What occurs is the following (assume just 2 procs)
1. proc A gets to execbuf while out of memory, gets struct_mutex.
2. OOM killer comes in and chooses proc B
3. proc B closes it's fds, which requires struct mutex, blocks
4, OOM killer waits for B to die before killing another process (this
part is speculative)
Cc: Daniel Vetter <daniel.vetter@xxxxxxxx>
Cc: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Ben Widawsky <ben@xxxxxxxxxxxx>
---
drivers/gpu/drm/i915/i915_gem.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index fb2d548..a60894d 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -1842,12 +1842,12 @@ i915_gem_object_get_pages_gtt(struct drm_i915_gem_object *obj)
BUG_ON(obj->base.read_domains & I915_GEM_GPU_DOMAINS);
BUG_ON(obj->base.write_domain & I915_GEM_GPU_DOMAINS);
- st = kmalloc(sizeof(*st), GFP_KERNEL);
+ st = kmalloc(sizeof(*st), GFP_NOWAIT);
if (st == NULL)
return -ENOMEM;
page_count = obj->base.size / PAGE_SIZE;
- if (sg_alloc_table(st, page_count, GFP_KERNEL)) {
+ if (sg_alloc_table(st, page_count, GFP_NOWAIT)) {
kfree(st);
return -ENOMEM;
}
--
1.8.4.2
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