Messages in this thread Patch in this message | | | Date | Thu, 28 Feb 2008 02:12:26 -0800 (PST) | From | David Rientjes <> | Subject | Re: [RFC/PATCH 0/4] CPUSET driven CPU isolation |
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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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