Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
Merge tag 'smp-urgent-2023-09-02' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull CPU hotplug fix from Ingo Molnar:
"Fix a CPU hotplug related deadlock between the task which initiates
and controls a CPU hot-unplug operation vs. the CFS bandwidth timer"
* tag 'smp-urgent-2023-09-02' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
cpu/hotplug: Prevent self deadlock on CPU hot-unplug
+23
-1
+23
-1
kernel/cpu.c
+23
-1
kernel/cpu.c
···
1487
1487
return ret;
1488
1488
}
1489
1489
1490
+
struct cpu_down_work {
1491
+
unsigned int cpu;
1492
+
enum cpuhp_state target;
1493
+
};
1494
+
1495
+
static long __cpu_down_maps_locked(void *arg)
1496
+
{
1497
+
struct cpu_down_work *work = arg;
1498
+
1499
+
return _cpu_down(work->cpu, 0, work->target);
1500
+
}
1501
+
1490
1502
static int cpu_down_maps_locked(unsigned int cpu, enum cpuhp_state target)
1491
1503
{
1504
+
struct cpu_down_work work = { .cpu = cpu, .target = target, };
1505
+
1492
1506
/*
1493
1507
* If the platform does not support hotplug, report it explicitly to
1494
1508
* differentiate it from a transient offlining failure.
···
1511
1497
return -EOPNOTSUPP;
1512
1498
if (cpu_hotplug_disabled)
1513
1499
return -EBUSY;
1514
-
return _cpu_down(cpu, 0, target);
1500
+
1501
+
/*
1502
+
* Ensure that the control task does not run on the to be offlined
1503
+
* CPU to prevent a deadlock against cfs_b->period_timer.
1504
+
*/
1505
+
cpu = cpumask_any_but(cpu_online_mask, cpu);
1506
+
if (cpu >= nr_cpu_ids)
1507
+
return -EBUSY;
1508
+
return work_on_cpu(cpu, __cpu_down_maps_locked, &work);
1515
1509
}
1516
1510
1517
1511
static int cpu_down(unsigned int cpu, enum cpuhp_state target)