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    SubjectRe: [RFC/PATCH 0/4] CPUSET driven CPU isolation
    On Thu, 28 Feb 2008, David Rientjes wrote:

    > Should the kernel refuse to move some threads, such as the migration
    > or watchdog kthreads, out of the root cpuset where the mems can be
    > adjusted to disallow access to the cpu to which they are bound? This is
    > a quick way to cause a crash or soft lockup.
    >

    Something like this?
    ---
    include/linux/sched.h | 1 +
    kernel/cpuset.c | 5 ++++-
    kernel/kthread.c | 1 +
    kernel/sched.c | 6 ++++++
    4 files changed, 12 insertions(+), 1 deletions(-)

    diff --git a/include/linux/sched.h b/include/linux/sched.h
    --- a/include/linux/sched.h
    +++ b/include/linux/sched.h
    @@ -1464,6 +1464,7 @@ static inline void put_task_struct(struct task_struct *t)
    #define PF_SWAPWRITE 0x00800000 /* Allowed to write to swap */
    #define PF_SPREAD_PAGE 0x01000000 /* Spread page cache over cpuset */
    #define PF_SPREAD_SLAB 0x02000000 /* Spread some slab caches over cpuset */
    +#define PF_CPU_BOUND 0x04000000 /* Kthread bound to specific cpu */
    #define PF_MEMPOLICY 0x10000000 /* Non-default NUMA mempolicy */
    #define PF_MUTEX_TESTER 0x20000000 /* Thread belongs to the rt mutex tester */
    #define PF_FREEZER_SKIP 0x40000000 /* Freezer should not count it as freezeable */
    diff --git a/kernel/cpuset.c b/kernel/cpuset.c
    --- a/kernel/cpuset.c
    +++ b/kernel/cpuset.c
    @@ -1175,11 +1175,14 @@ static void cpuset_attach(struct cgroup_subsys *ss,
    struct mm_struct *mm;
    struct cpuset *cs = cgroup_cs(cont);
    struct cpuset *oldcs = cgroup_cs(oldcont);
    + int ret;

    mutex_lock(&callback_mutex);
    guarantee_online_cpus(cs, &cpus);
    - set_cpus_allowed(tsk, cpus);
    + ret = set_cpus_allowed(tsk, cpus);
    mutex_unlock(&callback_mutex);
    + if (ret < 0)
    + return;

    from = oldcs->mems_allowed;
    to = cs->mems_allowed;
    diff --git a/kernel/kthread.c b/kernel/kthread.c
    --- a/kernel/kthread.c
    +++ b/kernel/kthread.c
    @@ -180,6 +180,7 @@ void kthread_bind(struct task_struct *k, unsigned int cpu)
    wait_task_inactive(k);
    set_task_cpu(k, cpu);
    k->cpus_allowed = cpumask_of_cpu(cpu);
    + k->flags |= PF_CPU_BOUND;
    }
    EXPORT_SYMBOL(kthread_bind);

    diff --git a/kernel/sched.c b/kernel/sched.c
    --- a/kernel/sched.c
    +++ b/kernel/sched.c
    @@ -5345,6 +5345,12 @@ int set_cpus_allowed(struct task_struct *p, cpumask_t new_mask)
    goto out;
    }

    + if (unlikely((p->flags & PF_CPU_BOUND) && p != current &&
    + !cpus_equal(p->cpus_allowed, new_mask))) {
    + ret = -EINVAL;
    + goto out;
    + }
    +
    if (p->sched_class->set_cpus_allowed)
    p->sched_class->set_cpus_allowed(p, &new_mask);
    else {

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      Last update: 2008-02-28 11:15    [W:0.022 / U:59.440 seconds]
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