Messages in this thread Patch in this message | | | Date | Fri, 05 Aug 2011 17:01:37 -0700 | From | Greg KH <> | Subject | [07/55] SUNRPC: Fix a race between work-queue and rpc_killall_tasks |
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2.6.32-longterm review patch. If anyone has any objections, please let us know.
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From: Trond Myklebust <Trond.Myklebust@netapp.com>
commit b55c59892e1f3b6c7d4b9ccffb4263e1486fb990 upstream.
Since rpc_killall_tasks may modify the rpc_task's tk_action field without any locking, we need to be careful when dereferencing it.
Reported-by: Ben Greear <greearb@candelatech.com> Tested-by: Ben Greear <greearb@candelatech.com> Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
--- net/sunrpc/sched.c | 27 +++++++++++---------------- 1 file changed, 11 insertions(+), 16 deletions(-)
--- a/net/sunrpc/sched.c +++ b/net/sunrpc/sched.c @@ -613,30 +613,25 @@ static void __rpc_execute(struct rpc_tas BUG_ON(RPC_IS_QUEUED(task)); for (;;) { + void (*do_action)(struct rpc_task *); /* - * Execute any pending callback. + * Execute any pending callback first. */ - if (task->tk_callback) { - void (*save_callback)(struct rpc_task *); - - /* - * We set tk_callback to NULL before calling it, - * in case it sets the tk_callback field itself: - */ - save_callback = task->tk_callback; - task->tk_callback = NULL; - save_callback(task); - } else { + do_action = task->tk_callback; + task->tk_callback = NULL; + if (do_action == NULL) { /* * Perform the next FSM step. - * tk_action may be NULL when the task has been killed - * by someone else. + * tk_action may be NULL if the task has been killed. + * In particular, note that rpc_killall_tasks may + * do this at any time, so beware when dereferencing. */ - if (task->tk_action == NULL) + do_action = task->tk_action; + if (do_action == NULL) break; - task->tk_action(task); } + do_action(task); /* * Lockless check for whether task is sleeping or not.
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