aboutsummaryrefslogtreecommitdiff
path: root/kernel/cpu.c
diff options
context:
space:
mode:
authorOleg Nesterov <oleg@redhat.com>2010-03-15 10:10:23 +0100
committerIngo Molnar <mingo@elte.hu>2010-04-02 20:12:03 +0200
commit6a1bdc1b577ebcb65f6603c57f8347309bc4ab13 (patch)
tree516130eedf782dd14505bd111e06bcfad9923b07 /kernel/cpu.c
parent30da688ef6b76e01969b00608202fff1eed2accc (diff)
downloadlinux-2.6.34-ux500-6a1bdc1b577ebcb65f6603c57f8347309bc4ab13.tar.gz
sched: _cpu_down(): Don't play with current->cpus_allowed
_cpu_down() changes the current task's affinity and then recovers it at the end. The problems are well known: we can't restore old_allowed if it was bound to the now-dead-cpu, and we can race with the userspace which can change cpu-affinity during unplug. _cpu_down() should not play with current->cpus_allowed at all. Instead, take_cpu_down() can migrate the caller of _cpu_down() after __cpu_disable() removes the dying cpu from cpu_online_mask. Signed-off-by: Oleg Nesterov <oleg@redhat.com> Acked-by: Rafael J. Wysocki <rjw@sisk.pl> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> LKML-Reference: <20100315091023.GA9148@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'kernel/cpu.c')
-rw-r--r--kernel/cpu.c18
1 files changed, 6 insertions, 12 deletions
diff --git a/kernel/cpu.c b/kernel/cpu.c
index f8cced2692b..8d340faac38 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -163,6 +163,7 @@ static inline void check_for_tasks(int cpu)
}
struct take_cpu_down_param {
+ struct task_struct *caller;
unsigned long mod;
void *hcpu;
};
@@ -171,6 +172,7 @@ struct take_cpu_down_param {
static int __ref take_cpu_down(void *_param)
{
struct take_cpu_down_param *param = _param;
+ unsigned int cpu = (unsigned long)param->hcpu;
int err;
/* Ensure this CPU doesn't handle any more interrupts. */
@@ -181,6 +183,8 @@ static int __ref take_cpu_down(void *_param)
raw_notifier_call_chain(&cpu_chain, CPU_DYING | param->mod,
param->hcpu);
+ if (task_cpu(param->caller) == cpu)
+ move_task_off_dead_cpu(cpu, 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 +195,10 @@ static int __ref take_cpu_down(void *_param)
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 +209,6 @@ static int __ref _cpu_down(unsigned int cpu, int tasks_frozen)
if (!cpu_online(cpu))
return -EINVAL;
- if (!alloc_cpumask_var(&old_allowed, GFP_KERNEL))
- return -ENOMEM;
-
cpu_hotplug_begin();
set_cpu_active(cpu, false);
err = __raw_notifier_call_chain(&cpu_chain, CPU_DOWN_PREPARE | mod,
@@ -224,10 +225,6 @@ static int __ref _cpu_down(unsigned int cpu, int tasks_frozen)
goto out_release;
}
- /* Ensure that we are not runnable on dying cpu */
- cpumask_copy(old_allowed, &current->cpus_allowed);
- set_cpus_allowed_ptr(current, cpu_active_mask);
-
err = __stop_machine(take_cpu_down, &tcd_param, cpumask_of(cpu));
if (err) {
set_cpu_active(cpu, true);
@@ -236,7 +233,7 @@ static int __ref _cpu_down(unsigned int cpu, int tasks_frozen)
hcpu) == NOTIFY_BAD)
BUG();
- goto out_allowed;
+ goto out_release;
}
BUG_ON(cpu_online(cpu));
@@ -254,8 +251,6 @@ static int __ref _cpu_down(unsigned int cpu, int tasks_frozen)
check_for_tasks(cpu);
-out_allowed:
- set_cpus_allowed_ptr(current, old_allowed);
out_release:
cpu_hotplug_done();
if (!err) {
@@ -263,7 +258,6 @@ out_release:
hcpu) == NOTIFY_BAD)
BUG();
}
- free_cpumask_var(old_allowed);
return err;
}