On Mon, Jun 04, 2018 at 01:22:05PM -0700, Chris Takemura wrote: > Hi linux-nfs, > > I've got an NFS server that's behaving a little oddly -- it loses > threads to disk sleep at the rate of about 1 every 5 minutes. Threads > stuck in this state all have the same stack: > > [<ffffffffc069e4ce>] nfsd4_cstate_assign_replay.part.78+0x1e/0x30 [nfsd] > [<ffffffffc06a4ecc>] nfs4_preprocess_seqid_op+0xfc/0x190 [nfsd] > [<ffffffffc06a5bb6>] nfsd4_close+0x66/0x2c0 [nfsd] > [<ffffffffc06934fe>] nfsd4_proc_compound+0x3be/0x720 [nfsd] > [<ffffffffc067fec6>] nfsd_dispatch+0xd6/0x270 [nfsd] > [<ffffffffc04eef16>] svc_process_common+0x456/0x730 [sunrpc] > [<ffffffffc04ef2f5>] svc_process+0x105/0x1c0 [sunrpc] > [<ffffffffc067f8f0>] nfsd+0xf0/0x160 [nfsd] > [<ffffffffb109f158>] kthread+0xd8/0xf0 > [<ffffffffb181b6f5>] ret_from_fork+0x55/0x80 > [<ffffffffffffffff>] 0xffffffffffffffff Looks like they're trying to so->so_replay.rp_mutex but are getting stuck on it indefinitely. That mutex is supposed to be released by nfsd4_cstate_clear_replay(). So it's a matter of tracing through the callers to figure out if there's a codepath where one's called but not the other. There's no way out of the main op-processing loop in nfsd4_proc_compound() without calling nfsd4_cstate_clear_replay() at the end. I don't see it immediately. Most likely might be nfsd4_cstate_assign_replay getting called twice somehow. We could stick a WARN_ON_ONCE(cstate->replay_ownere) at the start of that function. Might also be interesting to know whether the problem's still reproduceable on a more recent kernel. --b. > > This is on ubuntu, with kernel version 4.4.0-119-generic > #143~14.04.1-Ubuntu. As you can tell from the backtrace, it's serving > NFS4. > > I've been increasing the thread count to compensate for the hung > threads -- note that the total number of threads doesn't affect the > rate of hangs, which is stubbornly constant. > > Do you have any idea what could be causing this, and how I can stop > it, preferably without interrupting service? > -- > 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 -- 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
