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,
--
Jeff Layton <jlayton@xxxxxxxxxx>
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