Date: Sun, 2 Apr 2006 21:09:10 +0200 From: Peter Holm <peter@holm.cc> To: Tor Egge <Tor.Egge@cvsup.no.freebsd.org> Cc: truckman@freebsd.org, current@freebsd.org Subject: Re: Livelock / softdep_flush "loop" Message-ID: <20060402190910.GA12759@peter.osted.lan> In-Reply-To: <20060402.180153.74658240.Tor.Egge@cvsup.no.freebsd.org> References: <20060402094431.GA81954@peter.osted.lan> <20060402.180153.74658240.Tor.Egge@cvsup.no.freebsd.org>
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On Sun, Apr 02, 2006 at 06:01:53PM +0000, Tor Egge wrote:
> > I managed to zoom in on the livelocks I've been seeing lately.
>
> According to the console log, process 708 has marked one dependency as being in
> progress, locked a vnode and then slept waiting for the softdep lock.
>
> softdep_flush() doesn't take into account that some of the remaining
> dependencies cannot be processed at once.
>
> Process 45 ended up looping inside softdep_flush(), never sleeping, always
> believing that more work could be done.
>
> The enclosed patch might help.
>
I'm testing it right now.
- Peter
> - Tor Egge
> Index: sys/ufs/ffs/ffs_softdep.c
> ===================================================================
> RCS file: /home/ncvs/src/sys/ufs/ffs/ffs_softdep.c,v
> retrieving revision 1.193
> diff -u -r1.193 ffs_softdep.c
> --- sys/ufs/ffs/ffs_softdep.c 12 Mar 2006 05:25:16 -0000 1.193
> +++ sys/ufs/ffs/ffs_softdep.c 2 Apr 2006 17:21:13 -0000
> @@ -718,6 +718,7 @@
> {
> struct mount *nmp;
> struct mount *mp;
> + struct ufsmount *ump;
> struct thread *td;
> int remaining;
> int vfslocked;
> @@ -752,7 +753,9 @@
> continue;
> vfslocked = VFS_LOCK_GIANT(mp);
> softdep_process_worklist(mp, 0);
> - remaining += VFSTOUFS(mp)->softdep_on_worklist;
> + ump = VFSTOUFS(mp);
> + remaining += ump->softdep_on_worklist -
> + ump->softdep_on_worklist_inprogress;
> VFS_UNLOCK_GIANT(vfslocked);
> mtx_lock(&mountlist_mtx);
> nmp = TAILQ_NEXT(mp, mnt_list);
> @@ -914,11 +917,13 @@
> if ((flags & LK_NOWAIT) == 0 || wk->wk_type != D_DIRREM)
> break;
> wk->wk_state |= INPROGRESS;
> + ump->softdep_on_worklist_inprogress++;
> FREE_LOCK(&lk);
> ffs_vget(mp, WK_DIRREM(wk)->dm_oldinum,
> LK_NOWAIT | LK_EXCLUSIVE, &vp);
> ACQUIRE_LOCK(&lk);
> wk->wk_state &= ~INPROGRESS;
> + ump->softdep_on_worklist_inprogress--;
> if (vp != NULL)
> break;
> }
> Index: sys/ufs/ufs/ufsmount.h
> ===================================================================
> RCS file: /home/ncvs/src/sys/ufs/ufs/ufsmount.h,v
> retrieving revision 1.36
> diff -u -r1.36 ufsmount.h
> --- sys/ufs/ufs/ufsmount.h 8 Mar 2006 23:43:39 -0000 1.36
> +++ sys/ufs/ufs/ufsmount.h 2 Apr 2006 17:21:13 -0000
> @@ -76,6 +76,7 @@
> struct workhead softdep_workitem_pending; /* softdep work queue */
> struct worklist *softdep_worklist_tail; /* Tail pointer for above */
> int softdep_on_worklist; /* Items on the worklist */
> + int softdep_on_worklist_inprogress; /* Busy items on worklist */
> int softdep_deps; /* Total dependency count */
> int softdep_accdeps; /* accumulated dep count */
> int softdep_req; /* Wakeup when deps hits 0. */
--
Peter Holm
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