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Remove bogus locking from DDB's "show lockedvnods" command: using

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synchronization primitives from inside DDB is generally a bad idea,
and in this case it frequently results in panics due to DDB commands
being executed from the sio fast interrupt context on a serial
console.  Replace the locking with a note that a lack of locking
means that DDB may get see inconsistent views of the mount and vnode
lists, which could also result in a panic.  More frequently,
though, this avoids a panic than causes it.

Discussed with ages ago:	bde
Approved by:			re (scottl)
This commit is contained in:
Robert Watson 2003-05-12 14:37:47 +00:00
parent 4680667e8d
commit 1964fb9ba2
1 changed files with 7 additions and 11 deletions
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18
sys/kern/vfs_subr.c
View file

@ -2881,28 +2881,24 @@ vprint(label, vp)
*/
DB_SHOW_COMMAND(lockedvnods, lockedvnodes)
{
struct thread *td = curthread; /* XXX */
struct mount *mp, *nmp;
struct vnode *vp;
/*
* Note: because this is DDB, we can't obey the locking semantics
* for these structures, which means we could catch an inconsistent
* state and dereference a nasty pointer. Not much to be done
* about that.
*/
printf("Locked vnodes\n");
mtx_lock(&mountlist_mtx);
for (mp = TAILQ_FIRST(&mountlist); mp != NULL; mp = nmp) {
if (vfs_busy(mp, LK_NOWAIT, &mountlist_mtx, td)) {
nmp = TAILQ_NEXT(mp, mnt_list);
continue;
}
mtx_lock(&mntvnode_mtx);
nmp = TAILQ_NEXT(mp, mnt_list);
TAILQ_FOREACH(vp, &mp->mnt_nvnodelist, v_nmntvnodes) {
if (VOP_ISLOCKED(vp, NULL))
vprint(NULL, vp);
}
mtx_unlock(&mntvnode_mtx);
mtx_lock(&mountlist_mtx);
nmp = TAILQ_NEXT(mp, mnt_list);
vfs_unbusy(mp, td);
}
mtx_unlock(&mountlist_mtx);
}
#endif