linux-kernel - [34-longterm 192/247] SUNRPC: Ensure we always run the tk_callback before tk

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Message-Id: <1308850515-15242-133-git-send-email-paul.gortmaker@windriver.com>
Date:	Thu, 23 Jun 2011 13:34:20 -0400
From:	Paul Gortmaker <paul.gortmaker@...driver.com>
To:	stable@...nel.org, linux-kernel@...r.kernel.org
Cc:	stable-review@...nel.org,
	Trond Myklebust <Trond.Myklebust@...app.com>,
	Paul Gortmaker <paul.gortmaker@...driver.com>
Subject: [34-longterm 192/247] SUNRPC: Ensure we always run the tk_callback before tk_action

From: Trond Myklebust <Trond.Myklebust@...app.com>

                   -------------------
    This is a commit scheduled for the next v2.6.34 longterm release.
    If you see a problem with using this for longterm, please comment.
                   -------------------

commit e020c6800c9621a77223bf2c1ff68180e41e8ebf upstream.

This fixes a race in which the task->tk_callback() puts the rpc_task
to sleep, setting a new callback. Under certain circumstances, the current
code may end up executing the task->tk_action before it gets round to the
callback.

Signed-off-by: Trond Myklebust <Trond.Myklebust@...app.com>
Signed-off-by: Paul Gortmaker <paul.gortmaker@...driver.com>
---
 net/sunrpc/sched.c |   14 ++++++--------
 1 files changed, 6 insertions(+), 8 deletions(-)

diff --git a/net/sunrpc/sched.c b/net/sunrpc/sched.c
index aae6907..03a5c9e 100644
--- a/net/sunrpc/sched.c
+++ b/net/sunrpc/sched.c
@@ -642,14 +642,12 @@ static void __rpc_execute(struct rpc_task *task)
 			save_callback = task->tk_callback;
 			task->tk_callback = NULL;
 			save_callback(task);
-		}
-
-		/*
-		 * Perform the next FSM step.
-		 * tk_action may be NULL when the task has been killed
-		 * by someone else.
-		 */
-		if (!RPC_IS_QUEUED(task)) {
+		} else {
+			/*
+			 * Perform the next FSM step.
+			 * tk_action may be NULL when the task has been killed
+			 * by someone else.
+			 */
 			if (task->tk_action == NULL)
 				break;
 			task->tk_action(task);
-- 
1.7.4.4

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