Michal Hocko wrote: > OK, this is the part I have missed. I didn't realize that the swapout > path, which is indeed PF_MEMALLOC, can get down to blk code which uses > mempools. A quick code travers shows that at least > make_request_fn = blk_queue_bio > blk_queue_bio > get_request > __get_request > > might do that. And in that case I agree that the above mentioned patch > has unintentional side effects and should be re-evaluated. David, what > do you think? An obvious fixup would be considering TIF_MEMDIE in > mempool_alloc explicitly. TIF_MEMDIE is racy. Since the OOM killer sets TIF_MEMDIE on only one thread, there is no guarantee that TIF_MEMDIE is set to the thread which is looping inside mempool_alloc(). And since __GFP_NORETRY is used (regardless of f9054c70d28bc214), out_of_memory() is not called via __alloc_pages_may_oom(). This means that the thread which is looping inside mempool_alloc() can't get TIF_MEMDIE unless TIF_MEMDIE is set by the OOM killer. Maybe set __GFP_NOMEMALLOC by default at mempool_alloc() and remove it at mempool_alloc() when fatal_signal_pending() is true? But that behavior can OOM-kill somebody else when current was not OOM-killed. Sigh... David Rientjes wrote: > On Wed, 13 Jul 2016, Mikulas Patocka wrote: > > > What are the real problems that f9054c70d28bc214b2857cf8db8269f4f45a5e23 > > tries to fix? > > > > It prevents the whole system from livelocking due to an oom killed process > stalling forever waiting for mempool_alloc() to return. No other threads > may be oom killed while waiting for it to exit. Is that concern still valid? We have the OOM reaper for CONFIG_MMU=y case. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>