From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754920Ab2H3SqD (ORCPT ); Thu, 30 Aug 2012 14:46:03 -0400 Received: from e33.co.us.ibm.com ([32.97.110.151]:54452 "EHLO e33.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754858Ab2H3Spo (ORCPT ); Thu, 30 Aug 2012 14:45:44 -0400 From: "Paul E. McKenney" To: linux-kernel@vger.kernel.org Cc: mingo@elte.hu, laijs@cn.fujitsu.com, dipankar@in.ibm.com, akpm@linux-foundation.org, mathieu.desnoyers@polymtl.ca, josh@joshtriplett.org, niv@us.ibm.com, tglx@linutronix.de, peterz@infradead.org, rostedt@goodmis.org, Valdis.Kletnieks@vt.edu, dhowells@redhat.com, eric.dumazet@gmail.com, darren@dvhart.com, fweisbec@gmail.com, sbw@mit.edu, patches@linaro.org, "Paul E. McKenney" Subject: [PATCH tip/core/rcu 5/5] rcu: Prevent initialization race in rcutorture kthreads Date: Thu, 30 Aug 2012 11:45:12 -0700 Message-Id: <1346352312-31987-5-git-send-email-paulmck@linux.vnet.ibm.com> X-Mailer: git-send-email 1.7.8 In-Reply-To: <1346352312-31987-1-git-send-email-paulmck@linux.vnet.ibm.com> References: <20120830184448.GA31753@linux.vnet.ibm.com> <1346352312-31987-1-git-send-email-paulmck@linux.vnet.ibm.com> X-Content-Scanned: Fidelis XPS MAILER x-cbid: 12083018-2398-0000-0000-000009EA37AC X-IBM-ISS-SpamDetectors: X-IBM-ISS-DetailInfo: BY=3.00000293; HX=3.00000196; KW=3.00000007; PH=3.00000001; SC=3.00000007; SDB=6.00169860; UDB=6.00038509; UTC=2012-08-30 18:45:38 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: "Paul E. McKenney" When you do something like "t = kthread_run(...)", it is possible that the kthread will start running before the assignment to "t" happens. If the child kthread expects to find a pointer to its task_struct in "t", it will then be fatally disappointed. This commit therefore switches such cases to kthread_create() followed by wake_up_process(), guaranteeing that the assignment happens before the child kthread starts running. Reported-by: Fengguang Wu Signed-off-by: Paul E. McKenney --- kernel/rcutorture.c | 10 ++++++---- 1 files changed, 6 insertions(+), 4 deletions(-) diff --git a/kernel/rcutorture.c b/kernel/rcutorture.c index 8ea2726..3e2adae 100644 --- a/kernel/rcutorture.c +++ b/kernel/rcutorture.c @@ -2028,14 +2028,15 @@ rcu_torture_init(void) /* Start up the kthreads. */ VERBOSE_PRINTK_STRING("Creating rcu_torture_writer task"); - writer_task = kthread_run(rcu_torture_writer, NULL, - "rcu_torture_writer"); + writer_task = kthread_create(rcu_torture_writer, NULL, + "rcu_torture_writer"); if (IS_ERR(writer_task)) { firsterr = PTR_ERR(writer_task); VERBOSE_PRINTK_ERRSTRING("Failed to create writer"); writer_task = NULL; goto unwind; } + wake_up_process(writer_task); fakewriter_tasks = kzalloc(nfakewriters * sizeof(fakewriter_tasks[0]), GFP_KERNEL); if (fakewriter_tasks == NULL) { @@ -2150,14 +2151,15 @@ rcu_torture_init(void) } if (shutdown_secs > 0) { shutdown_time = jiffies + shutdown_secs * HZ; - shutdown_task = kthread_run(rcu_torture_shutdown, NULL, - "rcu_torture_shutdown"); + shutdown_task = kthread_create(rcu_torture_shutdown, NULL, + "rcu_torture_shutdown"); if (IS_ERR(shutdown_task)) { firsterr = PTR_ERR(shutdown_task); VERBOSE_PRINTK_ERRSTRING("Failed to create shutdown"); shutdown_task = NULL; goto unwind; } + wake_up_process(shutdown_task); } i = rcu_torture_onoff_init(); if (i != 0) { -- 1.7.8