diff options
| author | Stanislav Kinsbursky <skinsbursky@parallels.com> | 2011-03-17 18:54:23 +0300 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@suse.de> | 2011-03-23 12:50:35 -0700 |
| commit | 1f4e44274e7d452f969a5ccaea9a00002d4eea0e (patch) | |
| tree | 0490f93f3fc0c3e8943e59fa1e1cabdd2edb0f19 | |
| parent | aef1b4e72dd2386b1d88190194ec370ed0d5aa24 (diff) | |
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>
| -rw-r--r-- | net/sunrpc/clnt.c | 4 |
1 files changed, 3 insertions, 1 deletions
diff --git a/net/sunrpc/clnt.c b/net/sunrpc/clnt.c index 92ce94f5146b..503fbbb05414 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); |