On Mon, 27 Oct 2014, Chris Friesen wrote: > There are details (stack traces, etc.) in the first message in the thread: > http://www.spinics.net/lists/linux-rt-users/msg12261.html > > > Originally we had thought that nfsd might have been implicated somehow, but it > seems like it was just a trigger (possibly by increasing the rate of sync > I/O). > > In the interest of full disclosure I should point out that we're using a > modified kernel so there is a chance that we have introduced the problem > ourselves. That said, we have not made significant changes to either ext4 or > jbd2. (Just a couple of minor cherry-picked bugfixes.) I don't think it's an ext4/jdb2 problem. > The relevant code paths are: > > Journal commit. The important thing here is that we set the PG_writeback on a > page, put the jbd2 journal head on BJ_Shadow list, then sleep waiting for page > writeback complete. If the page writeback never completes, then the journal > head never comes off the BJ_Shadow list. And that's what you need to investigate. The rest of the threads being stuck waiting for the journal writeback or inode->sem are just the consequence of it and have nothing to do with the root cause of the problem. ftrace with the block/writeback/jdb/ext4/sched tracepoints enabled should provide a first insight into the issue. Thanks, tglx -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
