[PATCH -rt 2/5] hotplug: Call cpu_unplug_begin() a little early
From: Yong Zhang <hidden>
Date: 2011-10-16 10:57:18
Also in:
lkml
Subsystem:
cpu hotplug, the rest · Maintainers:
Thomas Gleixner, Peter Zijlstra, Linus Torvalds
cpu_unplug_begin() should be called before CPU_DOWN_PREPARE, because at CPU_DOWN_PREPARE cpu_active is cleared and sched_domain is rebuilt, it will finally lead to thread 'sync_unplug' will be running on the cpu on which it's created. I found by an incorrect warning on smp_processor_id() called by sync_unplug/1, and trace shows below: (echo 1 > /sys/device/system/cpu/cpu1/online) bash-1664 [000] 83.136620: _cpu_down: Bind sync_unplug to cpu 1 bash-1664 [000] 83.136623: sched_wait_task: comm=sync_unplug/1 pid=1724 prio=120 bash-1664 [000] 83.136624: _cpu_down: Wake sync_unplug bash-1664 [000] 83.136629: sched_wakeup: comm=sync_unplug/1 pid=1724 prio=120 success=1 target_cpu=000 Signed-off-by: Yong Zhang <redacted> --- kernel/cpu.c | 16 +++++++--------- 1 files changed, 7 insertions(+), 9 deletions(-)
diff --git a/kernel/cpu.c b/kernel/cpu.c
index 83fb084..13066a3 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c@@ -337,22 +337,20 @@ static int __ref _cpu_down(unsigned int cpu, int tasks_frozen) return -EBUSY; } - err = __cpu_notify(CPU_DOWN_PREPARE | mod, hcpu, -1, &nr_calls); + cpu_hotplug_begin(); + err = cpu_unplug_begin(cpu); if (err) { - nr_calls--; - __cpu_notify(CPU_DOWN_FAILED | mod, hcpu, nr_calls, NULL); - printk("%s: attempt to take down CPU %u failed\n", - __func__, cpu); + printk("cpu_unplug_begin(%d) failed\n", cpu); goto out_cancel; } - cpu_hotplug_begin(); - err = cpu_unplug_begin(cpu); + err = __cpu_notify(CPU_DOWN_PREPARE | mod, hcpu, -1, &nr_calls); if (err) { nr_calls--; __cpu_notify(CPU_DOWN_FAILED | mod, hcpu, nr_calls, NULL); - printk("cpu_unplug_begin(%d) failed\n", cpu); - goto out_cancel; + printk("%s: attempt to take down CPU %u failed\n", + __func__, cpu); + goto out_release; } err = __stop_machine(take_cpu_down, &tcd_param, cpumask_of(cpu));
--
1.7.1