lkml.org 
[lkml]   [2012]   [Jul]   [8]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    Date
    From
    SubjectRe: [PATCH 1/2] acpi : cpu hot-remove returns error number when cpu_down() fails
    Hi Srivatsa,

    Thank you for your reviewing.

    2012/07/06 18:51, Srivatsa S. Bhat wrote:
    > On 07/06/2012 08:46 AM, Yasuaki Ishimatsu wrote:
    >> Even if cpu_down() fails, acpi_processor_remove() continues to remove the cpu.
    >
    > Ouch!
    >
    >> But in this case, it should return error number since some process may run on
    >> the cpu. If the cpu has a running process and the cpu is turned the power off,
    >> the system cannot work well.
    >>
    >> Signed-off-by: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>
    >>
    >> ---
    >> drivers/acpi/processor_driver.c | 18 ++++++++++++------
    >> 1 file changed, 12 insertions(+), 6 deletions(-)
    >>
    >> Index: linux-3.5-rc4/drivers/acpi/processor_driver.c
    >> ===================================================================
    >> --- linux-3.5-rc4.orig/drivers/acpi/processor_driver.c 2012-06-25 04:53:04.000000000 +0900
    >> +++ linux-3.5-rc4/drivers/acpi/processor_driver.c 2012-07-05 21:02:58.711285382 +0900
    >> @@ -610,7 +610,7 @@ err_free_pr:
    >> static int acpi_processor_remove(struct acpi_device *device, int type)
    >> {
    >> struct acpi_processor *pr = NULL;
    >> -
    >> + int ret;
    >>
    >> if (!device || !acpi_driver_data(device))
    >> return -EINVAL;
    >> @@ -621,8 +621,9 @@ static int acpi_processor_remove(struct
    >> goto free;
    >>
    >> if (type == ACPI_BUS_REMOVAL_EJECT) {
    >> - if (acpi_processor_handle_eject(pr))
    >> - return -EINVAL;
    >> + ret = acpi_processor_handle_eject(pr);
    >> + if (ret)
    >> + return ret;
    >> }
    >>
    >> acpi_processor_power_exit(pr, device);
    >> @@ -841,12 +842,17 @@ static acpi_status acpi_processor_hotadd
    >>
    >> static int acpi_processor_handle_eject(struct acpi_processor *pr)
    >> {
    >> - if (cpu_online(pr->id))
    >> - cpu_down(pr->id);
    >> + int ret;
    >> +
    >> + if (cpu_online(pr->id)) {
    >> + ret = cpu_down(pr->id);
    >> + if (ret)
    >> + return ret;
    >> + }
    >>
    >
    > Strictly speaking, this is not thorough enough. What prevents someone
    > from onlining that same cpu again, at this point?
    > So, IMHO, you need to wrap the contents of this function inside a
    > get_online_cpus()/put_online_cpus() block, to prevent anyone else
    > from messing with CPU hotplug at the same time.

    If I understand your comment by mistake, please let me know.
    If the contents is wrapped a inside get_online_cpus()/put_online_cpus() block
    as below, cpu_down() will stop since cpu_down() calls cpu_hotplug_begin() and
    cpu_hotplug_begin() waits for cpu_hotplug.refcount to become 0.

    + get_online_cpus()
    + if (cpu_online(pr->id)) {
    + ret = cpu_down(pr->id);
    + if (ret)
    + return ret;
    + }
    + put_online_cpus()

    I think following patch can prevent it correctly. How about the patch?

    ---
    drivers/acpi/processor_driver.c | 12 ++++++++++++
    kernel/cpu.c | 8 +++++---
    2 files changed, 17 insertions(+), 3 deletions(-)

    Index: linux-3.5-rc4/drivers/acpi/processor_driver.c
    ===================================================================
    --- linux-3.5-rc4.orig/drivers/acpi/processor_driver.c 2012-07-09 09:59:01.280211202 +0900
    +++ linux-3.5-rc4/drivers/acpi/processor_driver.c 2012-07-09 11:05:34.559859236 +0900
    @@ -844,14 +844,26 @@ static int acpi_processor_handle_eject(s
    {
    int ret;

    +retry:
    if (cpu_online(pr->id)) {
    ret = cpu_down(pr->id);
    if (ret)
    return ret;
    }

    + get_online_cpus();
    + /*
    + * Someone might online the cpu again at this point. So we check that
    + * cpu has been onlined or not. If cpu is online, we try to offline
    + * the cpu again.
    + */
    + if (cpu_online(pr->id)) {
    + put_online_cpus();
    + goto retry;
    + }
    arch_unregister_cpu(pr->id);
    acpi_unmap_lsapic(pr->id);
    + put_online_cpus();
    return ret;
    }
    #else
    Index: linux-3.5-rc4/kernel/cpu.c
    ===================================================================
    --- linux-3.5-rc4.orig/kernel/cpu.c 2012-07-09 09:59:01.280211202 +0900
    +++ linux-3.5-rc4/kernel/cpu.c 2012-07-09 09:59:02.903190965 +0900
    @@ -343,11 +343,13 @@ static int __cpuinit _cpu_up(unsigned in
    unsigned long mod = tasks_frozen ? CPU_TASKS_FROZEN : 0;
    struct task_struct *idle;

    - if (cpu_online(cpu) || !cpu_present(cpu))
    - return -EINVAL;
    -
    cpu_hotplug_begin();

    + if (cpu_online(cpu) || !cpu_present(cpu)) {
    + ret = -EINVAL;
    + goto out;
    + }
    +
    idle = idle_thread_get(cpu);
    if (IS_ERR(idle)) {
    ret = PTR_ERR(idle);


    \
     
     \ /
      Last update: 2012-07-09 05:21    [W:0.031 / U:93.124 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site