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    Subject[PATCH v3 21/52] x86, therm_throt.c: Remove unused therm_cpu_lock
    Date
    After fixing the CPU hotplug callback registration code, the callbacks
    invoked for each online CPU, during the initialization phase in
    thermal_throttle_init_device(), can no longer race with the actual CPU
    hotplug notifier callbacks (in thermal_throttle_cpu_callback). Hence the
    therm_cpu_lock is unnecessary now. Remove it.

    Cc: Tony Luck <tony.luck@intel.com>
    Cc: Borislav Petkov <bp@alien8.de>
    Cc: Thomas Gleixner <tglx@linutronix.de>
    Cc: Ingo Molnar <mingo@kernel.org>
    Cc: "H. Peter Anvin" <hpa@zytor.com>
    Cc: x86@kernel.org
    Cc: linux-edac@vger.kernel.org
    Suggested-by: Oleg Nesterov <oleg@redhat.com>
    Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
    ---

    arch/x86/kernel/cpu/mcheck/therm_throt.c | 13 -------------
    1 file changed, 13 deletions(-)

    diff --git a/arch/x86/kernel/cpu/mcheck/therm_throt.c b/arch/x86/kernel/cpu/mcheck/therm_throt.c
    index e05dfa3..d921b7e 100644
    --- a/arch/x86/kernel/cpu/mcheck/therm_throt.c
    +++ b/arch/x86/kernel/cpu/mcheck/therm_throt.c
    @@ -271,9 +271,6 @@ static void thermal_throttle_remove_dev(struct device *dev)
    sysfs_remove_group(&dev->kobj, &thermal_attr_group);
    }

    -/* Mutex protecting device creation against CPU hotplug: */
    -static DEFINE_MUTEX(therm_cpu_lock);
    -
    /* Get notified when a cpu comes on/off. Be hotplug friendly. */
    static int
    thermal_throttle_cpu_callback(struct notifier_block *nfb,
    @@ -289,18 +286,14 @@ thermal_throttle_cpu_callback(struct notifier_block *nfb,
    switch (action) {
    case CPU_UP_PREPARE:
    case CPU_UP_PREPARE_FROZEN:
    - mutex_lock(&therm_cpu_lock);
    err = thermal_throttle_add_dev(dev, cpu);
    - mutex_unlock(&therm_cpu_lock);
    WARN_ON(err);
    break;
    case CPU_UP_CANCELED:
    case CPU_UP_CANCELED_FROZEN:
    case CPU_DEAD:
    case CPU_DEAD_FROZEN:
    - mutex_lock(&therm_cpu_lock);
    thermal_throttle_remove_dev(dev);
    - mutex_unlock(&therm_cpu_lock);
    break;
    }
    return notifier_from_errno(err);
    @@ -321,17 +314,11 @@ static __init int thermal_throttle_init_device(void)

    cpu_notifier_register_begin();

    -#ifdef CONFIG_HOTPLUG_CPU
    - mutex_lock(&therm_cpu_lock);
    -#endif
    /* connect live CPUs to sysfs */
    for_each_online_cpu(cpu) {
    err = thermal_throttle_add_dev(get_cpu_device(cpu), cpu);
    WARN_ON(err);
    }
    -#ifdef CONFIG_HOTPLUG_CPU
    - mutex_unlock(&therm_cpu_lock);
    -#endif

    __register_hotcpu_notifier(&thermal_throttle_cpu_notifier);
    cpu_notifier_register_done();


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