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Violators will be prosecuted; Thu, 6 Feb 2014 08:15:05 +1000 Received: from d23relay03.au.ibm.com (d23relay03.au.ibm.com [9.190.235.21]) by d23dlp01.au.ibm.com (Postfix) with ESMTP id 02EF52CE8052 for ; Thu, 6 Feb 2014 09:15:05 +1100 (EST) Received: from d23av02.au.ibm.com (d23av02.au.ibm.com [9.190.235.138]) by d23relay03.au.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id s15MEpFN5833002 for ; Thu, 6 Feb 2014 09:14:51 +1100 Received: from d23av02.au.ibm.com (localhost [127.0.0.1]) by d23av02.au.ibm.com (8.14.4/8.14.4/NCO v10.0 AVout) with ESMTP id s15MF3ff003965 for ; Thu, 6 Feb 2014 09:15:04 +1100 Received: from srivatsabhat.in.ibm.com ([9.79.225.33]) by d23av02.au.ibm.com (8.14.4/8.14.4/NCO v10.0 AVin) with ESMTP id s15MEuN7003676; Thu, 6 Feb 2014 09:14:58 +1100 From: "Srivatsa S. Bhat" Subject: [PATCH 28/51] arm64, hw_breakpoint.c: Fix CPU hotplug callback registration To: paulus@samba.org, oleg@redhat.com, rusty@rustcorp.com.au, peterz@infradead.org, tglx@linutronix.de, akpm@linux-foundation.org Date: Thu, 06 Feb 2014 03:39:45 +0530 Message-ID: <20140205220944.19080.26519.stgit@srivatsabhat.in.ibm.com> In-Reply-To: <20140205220251.19080.92336.stgit@srivatsabhat.in.ibm.com> References: <20140205220251.19080.92336.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: 14020522-6102-0000-0000-000004E448B6 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20140205_171532_916164_1149A2C4 X-CRM114-Status: GOOD ( 12.48 ) X-Spam-Score: -4.7 (----) Cc: ego@linux.vnet.ibm.com, walken@google.com, linux@arm.linux.org.uk, Catalin Marinas , Will Deacon , linux-kernel@vger.kernel.org, Lorenzo Pieralisi , "Srivatsa S. Bhat" , tj@kernel.org, paulmck@linux.vnet.ibm.com, mingo@kernel.org, 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=-4.7 required=5.0 tests=BAYES_00, 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_maps_update_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_maps_update_done(); Fix the hw-breakpoint code in arm64 by using this latter form of callback registration. Cc: Catalin Marinas Cc: Will Deacon Cc: Lorenzo Pieralisi Cc: linux-arm-kernel@lists.infradead.org Signed-off-by: Srivatsa S. Bhat --- arch/arm64/kernel/hw_breakpoint.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/arch/arm64/kernel/hw_breakpoint.c b/arch/arm64/kernel/hw_breakpoint.c index f17f581..24e88d0 100644 --- a/arch/arm64/kernel/hw_breakpoint.c +++ b/arch/arm64/kernel/hw_breakpoint.c @@ -913,6 +913,8 @@ static int __init arch_hw_breakpoint_init(void) pr_info("found %d breakpoint and %d watchpoint registers.\n", core_num_brps, core_num_wrps); + cpu_maps_update_begin(); + /* * Reset the breakpoint resources. We assume that a halting * debugger will leave the world in a nice state for us. @@ -927,7 +929,10 @@ static int __init arch_hw_breakpoint_init(void) TRAP_HWBKPT, "hw-watchpoint handler"); /* Register hotplug notifier. */ - register_cpu_notifier(&hw_breakpoint_reset_nb); + __register_cpu_notifier(&hw_breakpoint_reset_nb); + + cpu_maps_update_done(); + /* Register cpu_suspend hw breakpoint restore hook */ cpu_suspend_set_dbg_restorer(hw_breakpoint_reset);