On Tue, 03 Aug 2010 14:40:15 -0400 Trond Myklebust <trond.myklebust@xxxxxxxxxx> wrote: > On Tue, 2010-08-03 at 13:24 -0400, Jeff Layton wrote: > > We got a report recently about a panic in RHEL5 (2.6.18 based kernel). > > The problem appears to be that a task_cleanup workqueue job ran and got > > passed a pointer to an xprt that had been freed. The bug is here in > > case anyone is interested in the details: > > > > https://bugzilla.redhat.com/show_bug.cgi?id=611938 > > > > The situation seems to be pretty difficult to reproduce, but I don't > > see anything that's intended to ensure that this doesn't occur in RHEL5 > > or mainline. The task_cleanup workqueue job doesn't hold a reference to > > the xprt, and the job isn't canceled when the xprt is torn down. > > > > Bruce had a look and suggested that we may need something like the > > patch below (pasted in, so it probably won't apply correctly). I've > > tested a backported version of it on RHEL5 and it seems to work fine. > > > > Is it reasonable to cancel task_cleanup when destroying the xprt? Or, > > am I missing something that should prevent this situation in mainline > > (and perhaps isn't in RHEL5's kernel). > > > > Any help is appreciated... > > > > -----------------------------[snip]--------------------------------- > > diff --git a/net/sunrpc/xprt.c b/net/sunrpc/xprt.c > > index dcd0132..2a1f664 100644 > > --- a/net/sunrpc/xprt.c > > +++ b/net/sunrpc/xprt.c > > @@ -1129,6 +1129,7 @@ static void xprt_destroy(struct kref *kref) > > rpc_destroy_wait_queue(&xprt->sending); > > rpc_destroy_wait_queue(&xprt->resend); > > rpc_destroy_wait_queue(&xprt->backlog); > > + cancel_work_sync(&xprt->task_cleanup); > > /* > > * Tear down transport state and free the rpc_xprt > > */ > > -----------------------------[snip]--------------------------------- > > > > Thanks, > > How about doing a wait_on_bit_lock(&xprt->state, XPRT_LOCKED,...) > instead? > I haven't quite grokked what XPRT_LOCKED is supposed to signify. What would be the advantage of doing that over just killing off the task_cleanup job? It seems like if we're tearing down the xprt then waiting for task_cleanup to run is sort of pointless -- xs_destroy will take care of closing the socket anyway. Also, if we do go that route, do we need a wake_up_bit call in xprt_clear_locked? Thanks, -- Jeff Layton <jlayton@xxxxxxxxxx> -- 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
