Messages in this thread Patch in this message | | | Date | Mon, 21 Mar 2011 16:07:08 -0700 | From | Greg KH <> | Subject | [69/87] RPC: killing RPC tasks races fixed |
| |
2.6.37-stable review patch. If anyone has any objections, please let us know.
------------------
From: Stanislav Kinsbursky <skinsbursky@parallels.com>
commit 8e26de238fd794c8ea56a5c98bf67c40cfeb051d upstream.
RPC task RPC_TASK_QUEUED bit is set must be checked before trying to wake up task rpc_killall_tasks() because task->tk_waitqueue can not be set (equal to NULL). Also, as Trond Myklebust mentioned, such approach (instead of checking tk_waitqueue to NULL) allows us to "optimise away the call to rpc_wake_up_queued_task() altogether for those tasks that aren't queued".
Here is an example of dereferencing of tk_waitqueue equal to NULL:
CPU 0 CPU 1 CPU 2 -------------------- --------------------- -------------------------- nfs4_run_open_task rpc_run_task rpc_execute rpc_set_active rpc_make_runnable (waiting) rpc_async_schedule nfs4_open_prepare nfs_wait_on_sequence nfs_umount_begin rpc_killall_tasks rpc_wake_up_task rpc_wake_up_queued_task spin_lock(tk_waitqueue == NULL) BUG() rpc_sleep_on spin_lock(&q->lock) __rpc_sleep_on task->tk_waitqueue = q
Signed-off-by: Stanislav Kinsbursky <skinsbursky@openvz.org> Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
--- net/sunrpc/clnt.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)
--- a/net/sunrpc/clnt.c +++ b/net/sunrpc/clnt.c @@ -436,7 +436,9 @@ void rpc_killall_tasks(struct rpc_clnt * if (!(rovr->tk_flags & RPC_TASK_KILLED)) { rovr->tk_flags |= RPC_TASK_KILLED; rpc_exit(rovr, -EIO); - rpc_wake_up_queued_task(rovr->tk_waitqueue, rovr); + if (RPC_IS_QUEUED(rovr)) + rpc_wake_up_queued_task(rovr->tk_waitqueue, + rovr); } } spin_unlock(&clnt->cl_lock);
| |