Date: Wed, 2 Oct 2002 20:32:01 -0700 (PDT) From: Don Lewis <dl-freebsd@catspoiler.org> To: e0026813@stud3.tuwien.ac.at Cc: current@FreeBSD.ORG Subject: Re: Junior Kernel Hacker page updated... Message-ID: <200210030332.g933W1vU017519@gw.catspoiler.org> In-Reply-To: <20021002214028.GA94673@frog.fafoe>
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On 2 Oct, Stefan Farfeleder wrote:
> /freebsd/current/src/sys/vm/uma_core.c:1307: could sleep with "filedesc structure" locked from /freebsd/current/src/sys/kern/kern_event.c:959
>
> at me and freezes badly at some point (no breaking into ddb possible).
> This is totally repeatable. Is anybody able to reproduce (and maybe
> fix) this?
It looks like the problem is that knote_attach() calls hashinit() while
holding the lock, and that hashinit() calls MALLOC(..., M_WAITOK).
Try the following patch:
Index: sys/kern/kern_event.c
===================================================================
RCS file: /home/ncvs/src/sys/kern/kern_event.c,v
retrieving revision 1.45
diff -u -r1.45 kern_event.c
--- sys/kern/kern_event.c 17 Aug 2002 02:36:16 -0000 1.45
+++ sys/kern/kern_event.c 3 Oct 2002 03:10:09 -0000
@@ -953,15 +953,27 @@
static void
knote_attach(struct knote *kn, struct filedesc *fdp)
{
- struct klist *list, *oldlist;
+ struct klist *list, *oldlist, *tmp_knhash;
+ u_long tmp_knhashmask;
int size, newsize;
FILEDESC_LOCK(fdp);
if (! kn->kn_fop->f_isfd) {
- if (fdp->fd_knhashmask == 0)
- fdp->fd_knhash = hashinit(KN_HASHSIZE, M_KQUEUE,
- &fdp->fd_knhashmask);
+ if (fdp->fd_knhashmask == 0) {
+ FILEDESC_UNLOCK(fdp);
+ tmp_knhash = hashinit(KN_HASHSIZE, M_KQUEUE,
+ &tmp_knhashmask);
+ FILEDESC_LOCK(fdp);
+ if (fdp->fd_knhashmask == 0) {
+ fdp->fd_knhash = tmp_knhash;
+ fdp->fd_knhashmask = tmp_knhashmask;
+ } else {
+ FILEDESC_UNLOCK(fdp);
+ free(tmp_knhash, M_KQUEUE);
+ FILEDESC_LOCK(fdp);
+ }
+ }
list = &fdp->fd_knhash[KN_HASH(kn->kn_id, fdp->fd_knhashmask)];
goto done;
}
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