On Mon, Oct 12, 2015 at 04:14:21PM -0400, Jeff Layton wrote: > On Mon, 12 Oct 2015 14:11:17 -0400 > "J. Bruce Fields" <bfields@xxxxxxxxxxxx> wrote: > > > On Fri, Oct 09, 2015 at 05:39:23PM -0400, Jeff Layton wrote: > > > On Fri, 9 Oct 2015 17:24:59 -0400 > > > "J. Bruce Fields" <bfields@xxxxxxxxxxxx> wrote: > > > > > > > On Sat, Oct 03, 2015 at 08:38:02AM -0400, Jeff Layton wrote: > > > > > I don't see any need to order callbacks with respect to one another. > > > > > > > > I thought the code in nfsd4_process_cb_update really depended on this. > > > > The locking it has is against nfsd threads, it probably assumes it's > > > > only run from a cb thread and that it's the only one running at a time. > > > > > > > > But I haven't reviewed it lately. > > > > > > > > --b. > > > > > > > > > > Yikes -- ok. That's not at all obvious. That should prob be documented > > > if so. > > > > Yes, my bad. > > > > > Yeah, ok...I guess you could end up with multiple threads racing to > > > tear down the cb_client and xprt and create a new one, and it looks > > > like the cl_cb_client and cl_cred pointers could get clobbered by new > > > ones in that case. > > > > > > Shouldn't be too hard to fix protecting those pointers with the > > > cl_lock. That said, I prob won't be able to spend time on it right now. > > > You can go ahead and drop that patch and I'll resend if/when I get > > > around to fixing that. > > > > What's the problem that this fixes exactly? > > > > Unnecessary serialization of callbacks? > > Not that that's necessarily a problem, but with the newer workqueue > implementation there is more overhead in running a single threaded > workqueue since it implies a rescuer thread and has to do extra work > to ensure that the jobs are run in sequential order. > > If that serialization is not actually needed, then it's better to move > it to a multithreaded workqueue. We'd still be serializing a lot of the same code, just using locks instead, wouldn't we? --b. -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
