From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Srivatsa S. Bhat" Subject: [PATCH v3 30/52] arm64, hw_breakpoint.c: Fix CPU hotplug callback registration Date: Tue, 11 Mar 2014 02:09:08 +0530 Message-ID: <20140310203907.10746.60164.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" Content-Transfer-Encoding: 7bit Return-path: Received: from e23smtp05.au.ibm.com ([202.81.31.147]:45291 "EHLO e23smtp05.au.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755121AbaCJUjz (ORCPT ); Mon, 10 Mar 2014 16:39:55 -0400 Received: from /spool/local by e23smtp05.au.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Tue, 11 Mar 2014 06:39:53 +1000 In-Reply-To: <20140310203312.10746.310.stgit@srivatsabhat.in.ibm.com> Sender: linux-arch-owner@vger.kernel.org List-ID: To: paulus@samba.org, oleg@redhat.com, rjw@rjwysocki.net, rusty@rustcorp.com.au, peterz@infradead.org, tglx@linutronix.de, akpm@linux-foundation.org Cc: paulmck@linux.vnet.ibm.com, tj@kernel.org, walken@google.com, ego@linux.vnet.ibm.com, linux@arm.linux.org.uk, linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, linux-pm@vger.kernel.org, linuxppc-dev@ozlabs.org, srivatsa.bhat@linux.vnet.ibm.com, Catalin Marinas , Lorenzo Pieralisi , Ingo Molnar , linux-arm-kernel@lists.infradead.org, Will Deacon "Srivatsa S. Bhat" 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 arm64 by using this latter form of callback registration. Cc: Catalin Marinas Cc: Lorenzo Pieralisi Cc: Ingo Molnar Cc: linux-arm-kernel@lists.infradead.org Acked-by: Will Deacon 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..bee7897 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_notifier_register_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_notifier_register_done(); + /* Register cpu_suspend hw breakpoint restore hook */ cpu_suspend_set_dbg_restorer(hw_breakpoint_reset); From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from e23smtp05.au.ibm.com ([202.81.31.147]:45291 "EHLO e23smtp05.au.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755121AbaCJUjz (ORCPT ); Mon, 10 Mar 2014 16:39:55 -0400 Received: from /spool/local by e23smtp05.au.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Tue, 11 Mar 2014 06:39:53 +1000 From: "Srivatsa S. Bhat" Subject: [PATCH v3 30/52] arm64, hw_breakpoint.c: Fix CPU hotplug callback registration Date: Tue, 11 Mar 2014 02:09:08 +0530 Message-ID: <20140310203907.10746.60164.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" Content-Transfer-Encoding: 7bit Sender: linux-arch-owner@vger.kernel.org List-ID: 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 Cc: paulmck@linux.vnet.ibm.com, tj@kernel.org, walken@google.com, ego@linux.vnet.ibm.com, linux@arm.linux.org.uk, linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, linux-pm@vger.kernel.org, linuxppc-dev@ozlabs.org, srivatsa.bhat@linux.vnet.ibm.com, Catalin Marinas , Lorenzo Pieralisi , linux-arm-kernel@lists.infradead.org, Will Deacon "Srivatsa S. Bhat" Message-ID: <20140310203908.HVLE88spg7hwVJVME8HtacGDiFye0iVOwF5hkzoNDLY@z> 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 arm64 by using this latter form of callback registration. Cc: Catalin Marinas Cc: Lorenzo Pieralisi Cc: Ingo Molnar Cc: linux-arm-kernel@lists.infradead.org Acked-by: Will Deacon 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..bee7897 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_notifier_register_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_notifier_register_done(); + /* Register cpu_suspend hw breakpoint restore hook */ cpu_suspend_set_dbg_restorer(hw_breakpoint_reset);