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| author | Stanislav Kinsbursky <skinsbursky@parallels.com> | 2011-03-17 18:54:23 +0300 |
|---|---|---|
| committer | Trond Myklebust <Trond.Myklebust@netapp.com> | 2011-03-17 12:39:00 -0400 |
| commit | 8e26de238fd794c8ea56a5c98bf67c40cfeb051d (patch) | |
| tree | 3c8d0e6b1e6e0782b13221ee6c39e5be09552dd9 /net | |
| parent | ba3c578de274a5438bafbce03f9225936698051c (diff) | |
| download | lwn-8e26de238fd794c8ea56a5c98bf67c40cfeb051d.tar.gz lwn-8e26de238fd794c8ea56a5c98bf67c40cfeb051d.zip | |
RPC: killing RPC tasks races fixed
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>
Cc: stable@kernel.org
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
Diffstat (limited to 'net')
| -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 edaf56e2ed29..e7a96e478f63 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); |