From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from e23smtp04.au.ibm.com (e23smtp04.au.ibm.com [202.81.31.146]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by ozlabs.org (Postfix) with ESMTPS id 6CFFB2C09D9 for ; Tue, 11 Mar 2014 07:41:27 +1100 (EST) Received: from /spool/local by e23smtp04.au.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Tue, 11 Mar 2014 06:41:27 +1000 Received: from d23relay04.au.ibm.com (d23relay04.au.ibm.com [9.190.234.120]) by d23dlp01.au.ibm.com (Postfix) with ESMTP id DFD5C2CE8046 for ; Tue, 11 Mar 2014 07:40:53 +1100 (EST) Received: from d23av03.au.ibm.com (d23av03.au.ibm.com [9.190.234.97]) by d23relay04.au.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id s2AKKr4a48627844 for ; Tue, 11 Mar 2014 07:20:53 +1100 Received: from d23av03.au.ibm.com (localhost [127.0.0.1]) by d23av03.au.ibm.com (8.14.4/8.14.4/NCO v10.0 AVout) with ESMTP id s2AKeq5J022577 for ; Tue, 11 Mar 2014 07:40:53 +1100 From: "Srivatsa S. Bhat" Subject: [PATCH v3 42/52] octeon, watchdog: Fix CPU hotplug callback registration To: paulus@samba.org, oleg@redhat.com, mingo@kernel.org, rjw@rjwysocki.net, rusty@rustcorp.com.au, peterz@infradead.org, tglx@linutronix.de, akpm@linux-foundation.org Date: Tue, 11 Mar 2014 02:10:43 +0530 Message-ID: <20140310204042.10746.60098.stgit@srivatsabhat.in.ibm.com> In-Reply-To: <20140310203312.10746.310.stgit@srivatsabhat.in.ibm.com> References: <20140310203312.10746.310.stgit@srivatsabhat.in.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Cc: linux-arch@vger.kernel.org, ego@linux.vnet.ibm.com, walken@google.com, linux@arm.linux.org.uk, linux-watchdog@vger.kernel.org, linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org, linuxppc-dev@ozlabs.org, Wim Van Sebroeck , "Srivatsa S. Bhat" , tj@kernel.org, paulmck@linux.vnet.ibm.com, Ingo Molnar List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Subsystems that want to register CPU hotplug callbacks, as well as perform initialization for the CPUs that are already online, often do it as shown below: get_online_cpus(); for_each_online_cpu(cpu) init_cpu(cpu); register_cpu_notifier(&foobar_cpu_notifier); put_online_cpus(); This is wrong, since it is prone to ABBA deadlocks involving the cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently with CPU hotplug operations). Instead, the correct and race-free way of performing the callback registration is: cpu_notifier_register_begin(); for_each_online_cpu(cpu) init_cpu(cpu); /* Note the use of the double underscored version of the API */ __register_cpu_notifier(&foobar_cpu_notifier); cpu_notifier_register_done(); Fix the watchdog code in octeon by using this latter form of callback registration. Cc: Wim Van Sebroeck Cc: Ingo Molnar Cc: linux-watchdog@vger.kernel.org Signed-off-by: Srivatsa S. Bhat --- drivers/watchdog/octeon-wdt-main.c | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-) diff --git a/drivers/watchdog/octeon-wdt-main.c b/drivers/watchdog/octeon-wdt-main.c index 4612088..4baf2d7 100644 --- a/drivers/watchdog/octeon-wdt-main.c +++ b/drivers/watchdog/octeon-wdt-main.c @@ -708,10 +708,13 @@ static int __init octeon_wdt_init(void) cpumask_clear(&irq_enabled_cpus); + cpu_notifier_register_begin(); for_each_online_cpu(cpu) octeon_wdt_setup_interrupt(cpu); - register_hotcpu_notifier(&octeon_wdt_cpu_notifier); + __register_hotcpu_notifier(&octeon_wdt_cpu_notifier); + cpu_notifier_register_done(); + out: return ret; } @@ -725,7 +728,8 @@ static void __exit octeon_wdt_cleanup(void) misc_deregister(&octeon_wdt_miscdev); - unregister_hotcpu_notifier(&octeon_wdt_cpu_notifier); + cpu_notifier_register_begin(); + __unregister_hotcpu_notifier(&octeon_wdt_cpu_notifier); for_each_online_cpu(cpu) { int core = cpu2core(cpu); @@ -734,6 +738,9 @@ static void __exit octeon_wdt_cleanup(void) /* Free the interrupt handler */ free_irq(OCTEON_IRQ_WDOG0 + core, octeon_wdt_poke_irq); } + + cpu_notifier_register_done(); + /* * Disable the boot-bus memory, the code it points to is soon * to go missing.