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Date: Fri, 16 Mar 2012 06:24:05 +0000
From: "Liu, Chuansheng" <chuansheng.liu@...el.com>
To: Peter Zijlstra <peterz@...radead.org>
CC: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
Yanmin Zhang <yanmin_zhang@...ux.intel.com>,
"tglx@...utronix.de" <tglx@...utronix.de>
Subject: RE: [PATCH] Fix the race between smp_call_function and CPU booting
> -----Original Message-----
> From: Peter Zijlstra [mailto:peterz@...radead.org]
> Sent: Thursday, March 15, 2012 6:47 PM
> To: Liu, Chuansheng
> Cc: linux-kernel@...r.kernel.org; Yanmin Zhang; tglx@...utronix.de
> Subject: RE: [PATCH] Fix the race between smp_call_function and CPU booting
>
> On Thu, 2012-03-15 at 00:11 +0000, Liu, Chuansheng wrote:
> >
> > > -----Original Message-----
> > > From: Peter Zijlstra [mailto:peterz@...radead.org]
> > > Sent: Wednesday, March 14, 2012 5:43 PM
> > > To: Liu, Chuansheng
> > > Cc: linux-kernel@...r.kernel.org; Yanmin Zhang; tglx@...utronix.de
> > > Subject: RE: [PATCH] Fix the race between smp_call_function and CPU
> > > booting
> > >
> > > On Wed, 2012-03-14 at 06:27 +0000, Liu, Chuansheng wrote:
> > > > On the unplug case, after set the CPU to !active, we do not need
> > > > IPI handling for the corresponding CPU before it is set to
> > > > offline. I did not find any impact that limiting the
> > > > smp_call_function just after CPU is active.
> > >
> > > Have a look at Alpha, it's flush_tlb_mm() can use
> > > smp_call_function(), in the !active,online case you very much still need to
> tlb flush that cpu.
> > >
> > > The fact that it works on a limited use case on x86 doesn't say
> > > anything much at all.
>
> > Thanks your pointing out, do you have any other perfect solution for this
> issue?
> > As for the stress test result, advancing the setting active before
> > setting online broken something either.
>
> I'm not sure I understand.. are you saying that commit
> 5fbd036b552f633abb394a319f7c62a5c86a9cd7 in tip/master broke
> something?
Yes. I did the stress test, the commit 5fbd036b552f633abb394a319f7c62a5c86a9cd7
broken something as below traces:
[ 721.989553] WARNING: at /root/r3_ics/hardware/intel/linux-2.6/arch/x86/kernel/smp.c:118 native_smp_send_reschedule+0x50/0x60()
[ 722.000923] Hardware name: Medfield
[ 722.004401] Modules linked in: atomisp lm3554 mt9m114 mt9e013 videobuf_vmalloc videobuf_core mac80211 cfg80211 compat btwilink st_drv
[ 722.016408] Pid: 18865, comm: workqueue_trust Not tainted 3.0.8-137166-g2639a16-dirty #1
[ 722.024486] Call Trace:
[ 722.026939] [<c1252287>] warn_slowpath_common+0x77/0x130
[ 722.032321] [<c121df70>] ? native_smp_send_reschedule+0x50/0x60
[ 722.038314] [<c121df70>] ? native_smp_send_reschedule+0x50/0x60
[ 722.044316] [<c1252362>] warn_slowpath_null+0x22/0x30
[ 722.049445] [<c121df70>] native_smp_send_reschedule+0x50/0x60
[ 722.055268] [<c124bacf>] try_to_wake_up+0x17f/0x390
[ 722.060225] [<c124bd34>] wake_up_process+0x14/0x20
[ 722.065091] [<c1277107>] kthread_stop+0x37/0x100
[ 722.069789] [<c126f5e0>] destroy_worker+0x50/0x90
[ 722.074573] [<c18c1b4d>] trustee_thread+0x3e3/0x4bf
[ 722.079524] [<c1277410>] ? wake_up_bit+0x90/0x90
[ 722.084224] [<c18c176a>] ? wait_trustee_state+0x91/0x91
[ 722.089520] [<c1276fc4>] kthread+0x74/0x80
[ 722.093694] [<c1276f50>] ? __init_kthread_worker+0x30/0x30
[ 722.099264] [<c18c7cfa>] kernel_thread_helper+0x6/0x10
[ 722.104474] ---[ end trace fa5bcc15ece677c6 ]---
Based on your patch, I did a little modification, how do you think of that?
diff --git a/arch/arm/kernel/smp.c b/arch/arm/kernel/smp.c
index cdeb727..d616ed5 100644
--- a/arch/arm/kernel/smp.c
+++ b/arch/arm/kernel/smp.c
@@ -295,13 +295,6 @@ asmlinkage void __cpuinit secondary_start_kernel(void)
*/
percpu_timer_setup();
- while (!cpu_active(cpu))
- cpu_relax();
-
- /*
- * cpu_active bit is set, so it's safe to enalbe interrupts
- * now.
- */
local_irq_enable();
local_fiq_enable();
diff --git a/arch/hexagon/kernel/smp.c b/arch/hexagon/kernel/smp.c
index c871a2c..0123c63 100644
--- a/arch/hexagon/kernel/smp.c
+++ b/arch/hexagon/kernel/smp.c
@@ -179,8 +179,6 @@ void __cpuinit start_secondary(void)
printk(KERN_INFO "%s cpu %d\n", __func__, current_thread_info()->cpu);
set_cpu_online(cpu, true);
- while (!cpumask_test_cpu(cpu, cpu_active_mask))
- cpu_relax();
local_irq_enable();
cpu_idle();
diff --git a/arch/s390/kernel/smp.c b/arch/s390/kernel/smp.c
index 2398ce6..b0e28c4 100644
--- a/arch/s390/kernel/smp.c
+++ b/arch/s390/kernel/smp.c
@@ -550,12 +550,6 @@ int __cpuinit start_secondary(void *cpuvoid)
S390_lowcore.restart_psw.addr =
PSW_ADDR_AMODE | (unsigned long) psw_restart_int_handler;
__ctl_set_bit(0, 28); /* Enable lowcore protection */
- /*
- * Wait until the cpu which brought this one up marked it
- * active before enabling interrupts.
- */
- while (!cpumask_test_cpu(smp_processor_id(), cpu_active_mask))
- cpu_relax();
local_irq_enable();
/* cpu_idle will call schedule for us */
cpu_idle();
diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index 66d250c..58f7816 100644
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -291,19 +291,6 @@ notrace static void __cpuinit start_secondary(void *unused)
per_cpu(cpu_state, smp_processor_id()) = CPU_ONLINE;
x86_platform.nmi_init();
- /*
- * Wait until the cpu which brought this one up marked it
- * online before enabling interrupts. If we don't do that then
- * we can end up waking up the softirq thread before this cpu
- * reached the active state, which makes the scheduler unhappy
- * and schedule the softirq thread on the wrong cpu. This is
- * only observable with forced threaded interrupts, but in
- * theory it could also happen w/o them. It's just way harder
- * to achieve.
- */
- while (!cpumask_test_cpu(smp_processor_id(), cpu_active_mask))
- cpu_relax();
-
/* enable local interrupts */
local_irq_enable();
diff --git a/kernel/cpu.c b/kernel/cpu.c
index 2060c6e..6bf1fd3 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -640,8 +640,10 @@ void set_cpu_present(unsigned int cpu, bool present)
void set_cpu_online(unsigned int cpu, bool online)
{
- if (online)
+ if (online) {
cpumask_set_cpu(cpu, to_cpumask(cpu_online_bits));
+ cpumask_set_cpu(cpu, to_cpumask(cpu_active_bits));
+ }
else
cpumask_clear_cpu(cpu, to_cpumask(cpu_online_bits));
}
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index b342f57..ef97881 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -5381,7 +5381,6 @@ static int __cpuinit sched_cpu_active(struct notifier_block *nfb,
unsigned long action, void *hcpu)
{
switch (action & ~CPU_TASKS_FROZEN) {
- case CPU_ONLINE:
case CPU_DOWN_FAILED:
set_cpu_active((long)hcpu, true);
return NOTIFY_OK;
--
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