linux-kernel - RE: [PATCH] Fix the race between smp_call

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Date:	Fri, 23 Mar 2012 12:06:22 +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>,
	"Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>
Subject: RE: [PATCH] Fix the race between smp_call_function and CPU booting

Sorry to not see your scripts in details.

If so, I has something wrong about merging your change of select_fallback_rq()?
I am using 3.0.8.

I indeed see the warning even with the change of select_fallback_rq().


> -----Original Message-----
> From: Peter Zijlstra [mailto:peterz@...radead.org]
> Sent: Friday, March 23, 2012 8:02 PM
> To: Liu, Chuansheng
> Cc: linux-kernel@...r.kernel.org; Yanmin Zhang; tglx@...utronix.de; Srivatsa S.
> Bhat
> Subject: RE: [PATCH] Fix the race between smp_call_function and CPU booting
> 
> On Fri, 2012-03-23 at 11:32 +0000, Liu, Chuansheng wrote:
> > In fact, I started two scripts running:
> > 1/ One script:
> > echo 0 > /sys/devices/system/cpuX/online echo 1 >
> > /sys/devices/system/cpuX/online Rerunning the above commands in loop
> >
> > 2/Another script:
> > echo 1 > /debug/smp_call_test
> > usleep 50000
> > Rerunning the above command in loop
> >
> > This race issue can be easy to be reproduced in several minutes; For
> > simplify your test as mine(just two CPUs), you can set other
> > non-booting CPUs as offline at first and just leave one non-booting CPU.
> 
> So this is exactly what I did and it ran for 30+ minutes without fail. I found I
> forgot to log the serial output so I just re-ran this to make sure. 10+ minutes
> and not a single WARN in the console output.
> 
> If I pop my change to select_fallback_rq() I can indeed trigger this:
> 
> ------------[ cut here ]------------
> WARNING: at /usr/src/linux-2.6/arch/x86/kernel/smp.c:120
> native_smp_send_reschedule+0x5b/0x60()
> Hardware name: X8DTN
> Modules linked in: [last unloaded: scsi_wait_scan]
> Pid: 1542, comm: abrtd Not tainted 3.3.0-01725-gd6eb054-dirty #63 Call Trace:
>  <IRQ>  [<ffffffff810775df>] warn_slowpath_common+0x7f/0xc0
> [<ffffffff8107763a>] warn_slowpath_null+0x1a/0x20  [<ffffffff8105f79b>]
> native_smp_send_reschedule+0x5b/0x60
>  [<ffffffff810aa67a>] try_to_wake_up+0x1fa/0x2c0  [<ffffffff810acaec>] ?
> sched_slice.isra.38+0x5c/0x90  [<ffffffff810aa795>]
> wake_up_process+0x15/0x20  [<ffffffff81085c6e>] process_timeout+0xe/0x10
> [<ffffffff81086cb3>] run_timer_softirq+0x143/0x460  [<ffffffff81384a94>] ?
> timerqueue_add+0x74/0xc0  [<ffffffff81085c60>] ? usleep_range+0x50/0x50
> [<ffffffff8107e81d>] __do_softirq+0xbd/0x290  [<ffffffff810c5e64>] ?
> clockevents_program_event+0x74/0x100
>  [<ffffffff810c72d4>] ? tick_program_event+0x24/0x30  [<ffffffff8194ba4c>]
> call_softirq+0x1c/0x30  [<ffffffff810433d5>] do_softirq+0x55/0x90
> [<ffffffff8107ed2e>] irq_exit+0x9e/0xe0  [<ffffffff8194c07e>]
> smp_apic_timer_interrupt+0x6e/0x99
>  [<ffffffff8194b107>] apic_timer_interrupt+0x67/0x70  <EOI> ---[ end trace
> d2b2cbf78c1ddd2e ]---
> 
> 
> But let me re-run with the select_fallback_rq() change and let it run
> for several hours while I go play outside..
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