Livelock / softdep_flush "loop"
Tor Egge
Tor.Egge at cvsup.no.freebsd.org
Sun Apr 2 18:01:58 UTC 2006
> 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.
- Tor Egge
-------------- next part --------------
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. */
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