This is a note to let you know that I've just added the patch titled
RPC: killing RPC tasks races fixed
to the 2.6.38-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
rpc-killing-rpc-tasks-races-fixed.patch
and it can be found in the queue-2.6.38 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <[email protected]> know about it.
>From 8e26de238fd794c8ea56a5c98bf67c40cfeb051d Mon Sep 17 00:00:00 2001
From: Stanislav Kinsbursky <[email protected]>
Date: Thu, 17 Mar 2011 18:54:23 +0300
Subject: RPC: killing RPC tasks races fixed
From: Stanislav Kinsbursky <[email protected]>
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 <[email protected]>
Signed-off-by: Trond Myklebust <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
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);
Patches currently in stable-queue which might be from [email protected]
are
queue-2.6.38/rpc-killing-rpc-tasks-races-fixed.patch
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