From patchwork Mon Mar 10 20:39:01 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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Bhat" Subject: [PATCH v3 29/52] x86, kvm: 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 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, Gleb Natapov , Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , x86@kernel.org, kvm@vger.kernel.org, Paolo Bonzini , "Srivatsa S. Bhat" Date: Tue, 11 Mar 2014 02:09:01 +0530 Message-ID: <20140310203901.10746.635.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> User-Agent: StGIT/0.14.3 MIME-Version: 1.0 X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 14031020-8878-0000-0000-00000B41351C Sender: linux-pm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pm@vger.kernel.org X-Spam-Status: No, score=-6.9 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_HI, T_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 kvm code in x86 by using this latter form of callback registration. Cc: Gleb Natapov Cc: Thomas Gleixner Cc: Ingo Molnar Cc: "H. Peter Anvin" Cc: x86@kernel.org Cc: kvm@vger.kernel.org Acked-by: Paolo Bonzini Signed-off-by: Srivatsa S. Bhat --- arch/x86/kvm/x86.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) -- To unsubscribe from this list: send the line "unsubscribe linux-pm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 2b85784..4db6f56 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -5365,7 +5365,8 @@ static void kvm_timer_init(void) int cpu; max_tsc_khz = tsc_khz; - register_hotcpu_notifier(&kvmclock_cpu_notifier_block); + + cpu_notifier_register_begin(); if (!boot_cpu_has(X86_FEATURE_CONSTANT_TSC)) { #ifdef CONFIG_CPU_FREQ struct cpufreq_policy policy; @@ -5382,6 +5383,10 @@ static void kvm_timer_init(void) pr_debug("kvm: max_tsc_khz = %ld\n", max_tsc_khz); for_each_online_cpu(cpu) smp_call_function_single(cpu, tsc_khz_changed, NULL, 1); + + __register_hotcpu_notifier(&kvmclock_cpu_notifier_block); + cpu_notifier_register_done(); + } static DEFINE_PER_CPU(struct kvm_vcpu *, current_vcpu);