From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933047Ab3APQLE (ORCPT ); Wed, 16 Jan 2013 11:11:04 -0500 Received: from youngberry.canonical.com ([91.189.89.112]:36906 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933034Ab3APQK6 (ORCPT ); Wed, 16 Jan 2013 11:10:58 -0500 From: Herton Ronaldo Krzesinski To: linux-kernel@vger.kernel.org, stable@vger.kernel.org, kernel-team@lists.ubuntu.com Cc: Trond Myklebust , Weston Andros Adamson , Tejun Heo , Bruce Fields , Herton Ronaldo Krzesinski Subject: [PATCH 207/222] SUNRPC: Ensure that we free the rpc_task after cleanups are done Date: Wed, 16 Jan 2013 13:56:47 -0200 Message-Id: <1358351822-7675-208-git-send-email-herton.krzesinski@canonical.com> X-Mailer: git-send-email 1.7.9.5 In-Reply-To: <1358351822-7675-1-git-send-email-herton.krzesinski@canonical.com> References: <1358351822-7675-1-git-send-email-herton.krzesinski@canonical.com> X-Extended-Stable: 3.5 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.5.7.3 -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: Herton Ronaldo Krzesinski --- net/sunrpc/sched.c | 27 +++++++++++++++++++++++---- 1 file changed, 23 insertions(+), 4 deletions(-) diff --git a/net/sunrpc/sched.c b/net/sunrpc/sched.c index eda32ae..fe2cf2f 100644 --- a/net/sunrpc/sched.c +++ b/net/sunrpc/sched.c @@ -915,16 +915,35 @@ struct rpc_task *rpc_new_task(const struct rpc_task_setup *setup_data) 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; + + rpc_release_calldata(task->tk_ops, task->tk_calldata); - if (task->tk_flags & RPC_TASK_DYNAMIC) { + 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) -- 1.7.9.5