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authorStanislav Kinsbursky <skinsbursky@parallels.com>2011-03-17 18:54:23 +0300
committerGreg Kroah-Hartman <gregkh@suse.de>2011-03-23 13:04:03 -0700
commitba3ffdc68b4c80fe4cc42bdae6040eca1067ebb2 (patch)
tree100337bcc302666463b79454d347e69e406aebbe /net
parentbac39af7892a94d7212ad9c5d269a6ac6d1d5fde (diff)
downloadlinux-linaro-stable-ba3ffdc68b4c80fe4cc42bdae6040eca1067ebb2.tar.gz
RPC: killing RPC tasks races fixed
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>
Diffstat (limited to 'net')
-rw-r--r--net/sunrpc/clnt.c4
1 files changed, 3 insertions, 1 deletions
diff --git a/net/sunrpc/clnt.c b/net/sunrpc/clnt.c
index 57d344cf2256..35d046b588f3 100644
--- a/net/sunrpc/clnt.c
+++ b/net/sunrpc/clnt.c
@@ -436,7 +436,9 @@ void rpc_killall_tasks(struct rpc_clnt *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);