From patchwork Fri Feb 14 07:51:09 2014 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Srivatsa S. 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Violators will be prosecuted; Fri, 14 Feb 2014 17:56:38 +1000 Received: from d23relay05.au.ibm.com (d23relay05.au.ibm.com [9.190.235.152]) by d23dlp03.au.ibm.com (Postfix) with ESMTP id E34223578056 for ; Fri, 14 Feb 2014 18:56:37 +1100 (EST) Received: from d23av04.au.ibm.com (d23av04.au.ibm.com [9.190.235.139]) by d23relay05.au.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id s1E7avYG2752918 for ; Fri, 14 Feb 2014 18:36:58 +1100 Received: from d23av04.au.ibm.com (localhost [127.0.0.1]) by d23av04.au.ibm.com (8.14.4/8.14.4/NCO v10.0 AVout) with ESMTP id s1E7uZWw002185 for ; Fri, 14 Feb 2014 18:56:37 +1100 Received: from srivatsabhat.in.ibm.com ([9.78.204.74]) by d23av04.au.ibm.com (8.14.4/8.14.4/NCO v10.0 AVin) with ESMTP id s1E7uRoE001246; Fri, 14 Feb 2014 18:56:29 +1100 From: "Srivatsa S. Bhat" Subject: [PATCH v2 09/52] arm, hw-breakpoint: Fix CPU hotplug callback registration To: paulus@samba.org, oleg@redhat.com, mingo@kernel.org, rusty@rustcorp.com.au, peterz@infradead.org, tglx@linutronix.de, akpm@linux-foundation.org Date: Fri, 14 Feb 2014 13:21:09 +0530 Message-ID: <20140214075108.22701.93980.stgit@srivatsabhat.in.ibm.com> In-Reply-To: <20140214074750.22701.47330.stgit@srivatsabhat.in.ibm.com> References: <20140214074750.22701.47330.stgit@srivatsabhat.in.ibm.com> User-Agent: StGIT/0.14.3 MIME-Version: 1.0 X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 14021407-7014-0000-0000-00000453A0C3 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20140214_025734_735954_D9BAA534 X-CRM114-Status: GOOD ( 15.09 ) X-Spam-Score: -4.5 (----) Cc: linux-arch@vger.kernel.org, ego@linux.vnet.ibm.com, walken@google.com, Russell King , Will Deacon , rjw@rjwysocki.net, linux-kernel@vger.kernel.org, "Srivatsa S. Bhat" , tj@kernel.org, paulmck@linux.vnet.ibm.com, Ingo Molnar , linux-arm-kernel@lists.infradead.org X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org X-Spam-Status: No, score=-1.8 required=5.0 tests=BAYES_00,KHOP_BIG_TO_CC, RCVD_IN_DNSWL_MED, RP_MATCHES_RCVD, UNPARSEABLE_RELAY autolearn=unavailable version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP 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 hw-breakpoint code in arm by using this latter form of callback registration. Cc: Russell King Cc: Ingo Molnar Cc: linux-arm-kernel@lists.infradead.org Acked-by: Will Deacon Signed-off-by: Srivatsa S. Bhat --- arch/arm/kernel/hw_breakpoint.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/arch/arm/kernel/hw_breakpoint.c b/arch/arm/kernel/hw_breakpoint.c index 3d44660..3702de8 100644 --- a/arch/arm/kernel/hw_breakpoint.c +++ b/arch/arm/kernel/hw_breakpoint.c @@ -1072,6 +1072,8 @@ static int __init arch_hw_breakpoint_init(void) core_num_brps = get_num_brps(); core_num_wrps = get_num_wrps(); + cpu_notifier_register_begin(); + /* * We need to tread carefully here because DBGSWENABLE may be * driven low on this core and there isn't an architected way to @@ -1088,6 +1090,7 @@ static int __init arch_hw_breakpoint_init(void) if (!cpumask_empty(&debug_err_mask)) { core_num_brps = 0; core_num_wrps = 0; + cpu_notifier_register_done(); return 0; } @@ -1107,7 +1110,10 @@ static int __init arch_hw_breakpoint_init(void) TRAP_HWBKPT, "breakpoint debug exception"); /* Register hotplug and PM notifiers. */ - register_cpu_notifier(&dbg_reset_nb); + __register_cpu_notifier(&dbg_reset_nb); + + cpu_notifier_register_done(); + pm_init(); return 0; }