On Mon, 12 Dec 2011 18:16:48 -0800 Ying Han <yinghan@xxxxxxxxxx> wrote: > Couple of kernel dumps are triggered by watchdog timeout. It turns out that two > processes within a memcg livelock on a same page lock. We believe this is not > memcg specific issue and the same livelock exists in non-memcg world as well. > > The sequence of triggering the livelock: > 1. Task_A enters pagefault (filemap_fault) and then starts readahead > filemap_fault > -> do_sync_mmap_readahead > -> ra_submit > ->__do_page_cache_readahead // here we allocate the readahead pages > ->read_pages > ... > ->add_to_page_cache_locked > //for each page, we do the try charge and then add the page into > //radix tree. If one of the try charge failed, it enters per-memcg > //oom while holding the page lock of previous readahead pages. > > // in the memcg oom killer, it picks a task within the same memcg > // and mark it TIF_MEMDIE. then it goes back into retry loop and > // hopes the task exits to free some memory. > > 2. Task_B enters pagefault (filemap_fault) and finds the page in radix tree ( > one of the readahead pages from ProcessA) > > filemap_fault > ->__lock_page // here it is marked as TIF_MEMDIE. but it can not proceed since > // the page lock is hold by ProcessA looping at OOM. > Should this __lock_page() be lock_page_killable() ? Hmm, at seeing linux-next, it's now lock_page_or_retry() and FAULT_FLAG_KILLABLE is set. why not killed immediately ? Thanks, -Kame -- 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/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>