Re: [PATCH] RPC: killing RPC tasks races fixed
From: Trond Myklebust <hidden>
Date: 2011-03-17 16:44:21
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On Thu, 2011-03-17 at 18:43 +0300, Stanislav Kinsbursky wrote:
17.03.2011 16:01, Trond Myklebust пишет:quoted
On Thu, 2011-03-17 at 15:16 +0300, Stanislav Kinsbursky wrote:quoted
task->tk_waitqueue must be checked for NULL before trying to wake up task in rpc_killall_tasks() because it can be NULL. Here is an example: 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<redacted> --- 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 57d344c..24039fe 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 (rovr->tk_waitqueue) + rpc_wake_up_queued_task(rovr->tk_waitqueue, + rovr);Testing for RPC_IS_QUEUED(rovr) would be better, since that would optimise away the call to rpc_wake_up_queued_task() altogether for those tasks that aren't queued.Yes, I agree with testing RPC_IS_QUEUED(rovr) since such approach looks clearer and in 2.6.38 tk_waitqueue is initialized prior to set RPC_TASK_QUEUED bit. But I found this problem in 2.6.32 rhel kernel where this set sequence is inversed. Will send fixed version soon.
Are you sure? Why would the 2.6.32 rhel kernel differ from the mainline 2.6.32 kernel in this respect? -- Trond Myklebust Linux NFS client maintainer NetApp Trond.Myklebust-HgOvQuBEEgTQT0dZR+AlfA@public.gmane.org www.netapp.com -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html