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 <[email protected]> Cc: Chris Wilson <[email protected]> Signed-off-by: Ben Widawsky <[email protected]> --- 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 _______________________________________________ Intel-gfx mailing list [email protected] http://lists.freedesktop.org/mailman/listinfo/intel-gfx
