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    Subject[PATCH 02/12] cpu-hotplug: return better errno on cpu hotplug failure
    Date
    Currently, onlining or offlining a CPU failure by one of the cpu
    notifiers error always cause -EINVAL error.
    (i.e. writing 0 or 1 to /sys/devices/system/cpu/cpuX/online gets EINVAL)

    To get better error reporting rather than always getting -EINVAL,
    This changes cpu_notify() to return -errno value with notifier_to_errno() and
    fix the callers. Now that cpu notifiers can return encapsulate errno value.

    Currently, all cpu hotplug notifiers return NOTIFY_OK, NOTIFY_BAD,
    or NOTIFY_DONE. So cpu_notify() can returns 0 or -EPERM with this change
    for now.
    (notifier_to_errno(NOTIFY_OK) == 0, notifier_to_errno(NOTIFY_DONE) == 0,
    notifier_to_errno(NOTIFY_BAD) == -EPERM)

    Forthcoming patches convert several cpu notifiers to return encapsulate
    errno value with notifier_from_errno().

    Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
    Cc: Rusty Russell <rusty@rustcorp.com.au>
    ---
    kernel/cpu.c | 14 ++++++++------
    1 files changed, 8 insertions(+), 6 deletions(-)

    diff --git a/kernel/cpu.c b/kernel/cpu.c
    index bc9c301..d3f335e 100644
    --- a/kernel/cpu.c
    +++ b/kernel/cpu.c
    @@ -136,8 +136,12 @@ int __ref register_cpu_notifier(struct notifier_block *nb)
    static int __cpu_notify(unsigned long val, void *v, int nr_to_call,
    int *nr_calls)
    {
    - return __raw_notifier_call_chain(&cpu_chain, val, v, nr_to_call,
    + int ret;
    +
    + ret = __raw_notifier_call_chain(&cpu_chain, val, v, nr_to_call,
    nr_calls);
    +
    + return notifier_to_errno(ret);
    }

    static int cpu_notify(unsigned long val, void *v)
    @@ -150,7 +154,7 @@ static void cpu_notify_nofail(unsigned long val, void *v)
    int err;

    err = cpu_notify(val, v);
    - BUG_ON(err == NOTIFY_BAD);
    + BUG_ON(err);
    }

    #ifdef CONFIG_HOTPLUG_CPU
    @@ -230,14 +234,13 @@ static int __ref _cpu_down(unsigned int cpu, int tasks_frozen)
    cpu_hotplug_begin();
    set_cpu_active(cpu, false);
    err = __cpu_notify(CPU_DOWN_PREPARE | mod, hcpu, -1, &nr_calls);
    - if (err == NOTIFY_BAD) {
    + if (err) {
    set_cpu_active(cpu, true);

    nr_calls--;
    __cpu_notify(CPU_DOWN_FAILED | mod, hcpu, nr_calls, NULL);
    printk("%s: attempt to take down CPU %u failed\n",
    __func__, cpu);
    - err = -EINVAL;
    goto out_release;
    }

    @@ -314,11 +317,10 @@ static int __cpuinit _cpu_up(unsigned int cpu, int tasks_frozen)

    cpu_hotplug_begin();
    ret = __cpu_notify(CPU_UP_PREPARE | mod, hcpu, -1, &nr_calls);
    - if (ret == NOTIFY_BAD) {
    + if (ret) {
    nr_calls--;
    printk("%s: attempt to bring up CPU %u failed\n",
    __func__, cpu);
    - ret = -EINVAL;
    goto out_notify;
    }

    --
    1.6.0.6


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