Re: [PATCH] RPC: killing RPC tasks races fixed
From: Trond Myklebust <hidden>
Date: 2011-03-17 13:02:51
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linux-nfs, lkml
On Thu, 2011-03-17 at 15:16 +0300, Stanislav Kinsbursky wrote:
quoted hunk ↗ jump to hunk
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.
} } spin_unlock(&clnt->cl_lock);
-- 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