From fd537e56f65c61bb4cece99ac3a1a1bef6676df9 Mon Sep 17 00:00:00 2001 From: "Srivatsa S. Bhat" Date: Tue, 11 Mar 2014 02:08:09 +0530 Subject: [PATCH] x86, intel, rapl: Fix CPU hotplug callback registration 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 intel rapl code in x86 by using this latter form of callback registration. Cc: Peter Zijlstra Cc: Paul Mackerras Cc: Ingo Molnar Cc: Arnaldo Carvalho de Melo Cc: Thomas Gleixner Cc: "H. Peter Anvin" Signed-off-by: Srivatsa S. Bhat Signed-off-by: Rafael J. Wysocki --- arch/x86/kernel/cpu/perf_event_intel_rapl.c | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-) diff --git a/arch/x86/kernel/cpu/perf_event_intel_rapl.c b/arch/x86/kernel/cpu/perf_event_intel_rapl.c index 5ad35ad94d0f..059218ed5208 100644 --- a/arch/x86/kernel/cpu/perf_event_intel_rapl.c +++ b/arch/x86/kernel/cpu/perf_event_intel_rapl.c @@ -646,19 +646,20 @@ static int __init rapl_pmu_init(void) /* unsupported */ return 0; } - get_online_cpus(); + + cpu_notifier_register_begin(); for_each_online_cpu(cpu) { rapl_cpu_prepare(cpu); rapl_cpu_init(cpu); } - perf_cpu_notifier(rapl_cpu_notifier); + __perf_cpu_notifier(rapl_cpu_notifier); ret = perf_pmu_register(&rapl_pmu_class, "power", -1); if (WARN_ON(ret)) { pr_info("RAPL PMU detected, registration failed (%d), RAPL PMU disabled\n", ret); - put_online_cpus(); + cpu_notifier_register_done(); return -1; } @@ -672,7 +673,7 @@ static int __init rapl_pmu_init(void) hweight32(rapl_cntr_mask), ktime_to_ms(pmu->timer_interval)); - put_online_cpus(); + cpu_notifier_register_done(); return 0; } -- 2.34.1