lkml.org 
[lkml]   [2009]   [Jul]   [28]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    Date
    From
    SubjectRe: + cpu_hotplug-dont-affect-current-tasks-affinity.patch added to -mm tree
    Noticed this patch by accident...

    > Subject: cpu_hotplug: don't affect current task's affinity
    > From: Lai Jiangshan <laijs@cn.fujitsu.com>
    >
    > _cpu_down() changes the current task's affinity and then recovers it at
    > the end.
    >
    > It has two problems:

    Yes.

    But can't we make a much more simple patch ?

    Why should we play with set_cpus_allowed() at all? We can just migrate
    the caller of _cpu_down() before other tasks, right after take_cpu_down()
    does __cpu_disable()->remove_cpu_from_maps().

    No?

    Oleg.

    ------------------------------------------------------------------------
    Uncompiled, and we need to export move_task_off_dead_cpu(). Just to
    explain what I mean.

    kernel/cpu.c | 18 +++++-------------
    1 file changed, 5 insertions(+), 13 deletions(-)

    --- a/kernel/cpu.c
    +++ b/kernel/cpu.c
    @@ -163,6 +163,7 @@ static inline void check_for_tasks(int c
    }

    struct take_cpu_down_param {
    + struct task_struct *caller;
    unsigned long mod;
    void *hcpu;
    };
    @@ -181,6 +182,8 @@ static int __ref take_cpu_down(void *_pa
    raw_notifier_call_chain(&cpu_chain, CPU_DYING | param->mod,
    param->hcpu);

    + move_task_off_dead_cpu(param->hcpu, param->caller);
    +
    /* Force idle task to run as soon as we yield: it should
    immediately notice cpu is offline and die quickly. */
    sched_idle_next();
    @@ -191,10 +194,10 @@ static int __ref take_cpu_down(void *_pa
    static int __ref _cpu_down(unsigned int cpu, int tasks_frozen)
    {
    int err, nr_calls = 0;
    - cpumask_var_t old_allowed;
    void *hcpu = (void *)(long)cpu;
    unsigned long mod = tasks_frozen ? CPU_TASKS_FROZEN : 0;
    struct take_cpu_down_param tcd_param = {
    + .caller = current,
    .mod = mod,
    .hcpu = hcpu,
    };
    @@ -205,9 +208,6 @@ static int __ref _cpu_down(unsigned int
    if (!cpu_online(cpu))
    return -EINVAL;

    - if (!alloc_cpumask_var(&old_allowed, GFP_KERNEL))
    - return -ENOMEM;
    -
    cpu_hotplug_begin();
    err = __raw_notifier_call_chain(&cpu_chain, CPU_DOWN_PREPARE | mod,
    hcpu, -1, &nr_calls);
    @@ -221,11 +221,6 @@ static int __ref _cpu_down(unsigned int
    goto out_release;
    }

    - /* Ensure that we are not runnable on dying cpu */
    - cpumask_copy(old_allowed, &current->cpus_allowed);
    - set_cpus_allowed_ptr(current,
    - cpumask_of(cpumask_any_but(cpu_online_mask, cpu)));
    -
    err = __stop_machine(take_cpu_down, &tcd_param, cpumask_of(cpu));
    if (err) {
    /* CPU didn't die: tell everyone. Can't complain. */
    @@ -233,7 +228,7 @@ static int __ref _cpu_down(unsigned int
    hcpu) == NOTIFY_BAD)
    BUG();

    - goto out_allowed;
    + goto out_release;
    }
    BUG_ON(cpu_online(cpu));

    @@ -251,8 +246,6 @@ static int __ref _cpu_down(unsigned int

    check_for_tasks(cpu);

    -out_allowed:
    - set_cpus_allowed_ptr(current, old_allowed);
    out_release:
    cpu_hotplug_done();
    if (!err) {
    @@ -260,7 +253,6 @@ out_release:
    hcpu) == NOTIFY_BAD)
    BUG();
    }
    - free_cpumask_var(old_allowed);
    return err;
    }



    \
     
     \ /
      Last update: 2009-07-29 04:39    [W:0.022 / U:179.952 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site