From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Greg Kroah-Hartman , alan@lxorguk.ukuu.org.uk, Trond Myklebust , Weston Andros Adamson , Tejun Heo , Bruce Fields Subject: [ 063/221] SUNRPC: Ensure that we free the rpc_task after cleanups are done Date: Tue, 15 Jan 2013 10:49:50 -0800 Message-Id: <20130115185002.600044202@linuxfoundation.org> In-Reply-To: <20130115184958.025580322@linuxfoundation.org> References: <20130115184958.025580322@linuxfoundation.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: 3.7-stable review patch. If anyone has any objections, please let me know. ------------------ From: Trond Myklebust commit c6567ed1402c55e19b012e66a8398baec2a726f3 upstream. This patch ensures that we free the rpc_task after the cleanup callbacks are done in order to avoid a deadlock problem that can be triggered if the callback needs to wait for another workqueue item to complete. Signed-off-by: Trond Myklebust Cc: Weston Andros Adamson Cc: Tejun Heo Cc: Bruce Fields Signed-off-by: Greg Kroah-Hartman --- net/sunrpc/sched.c | 27 +++++++++++++++++++++++---- 1 file changed, 23 insertions(+), 4 deletions(-) --- a/net/sunrpc/sched.c +++ b/net/sunrpc/sched.c @@ -919,16 +919,35 @@ struct rpc_task *rpc_new_task(const stru return task; } +/* + * rpc_free_task - release rpc task and perform cleanups + * + * Note that we free up the rpc_task _after_ rpc_release_calldata() + * in order to work around a workqueue dependency issue. + * + * Tejun Heo states: + * "Workqueue currently considers two work items to be the same if they're + * on the same address and won't execute them concurrently - ie. it + * makes a work item which is queued again while being executed wait + * for the previous execution to complete. + * + * If a work function frees the work item, and then waits for an event + * which should be performed by another work item and *that* work item + * recycles the freed work item, it can create a false dependency loop. + * There really is no reliable way to detect this short of verifying + * every memory free." + * + */ static void rpc_free_task(struct rpc_task *task) { - const struct rpc_call_ops *tk_ops = task->tk_ops; - void *calldata = task->tk_calldata; + unsigned short tk_flags = task->tk_flags; - if (task->tk_flags & RPC_TASK_DYNAMIC) { + rpc_release_calldata(task->tk_ops, task->tk_calldata); + + if (tk_flags & RPC_TASK_DYNAMIC) { dprintk("RPC: %5u freeing task\n", task->tk_pid); mempool_free(task, rpc_task_mempool); } - rpc_release_calldata(tk_ops, calldata); } static void rpc_async_release(struct work_struct *work)