linux-kernel - Re: [Bug #10815] 2.6.26-rc4: RIP find_pid

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Message-ID: <20080617034228.GA18217@linux.vnet.ibm.com>
Date:	Mon, 16 Jun 2008 20:42:28 -0700
From:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:	Alexey Dobriyan <adobriyan@...il.com>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Oleg Nesterov <oleg@...sign.ru>, Adrian Bunk <bunk@...nel.org>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [Bug #10815] 2.6.26-rc4: RIP find_pid_ns+0x6b/0xa0

On Mon, Jun 16, 2008 at 07:46:59AM +0400, Alexey Dobriyan wrote:
> On Sun, Jun 15, 2008 at 08:31:26PM -0700, Paul E. McKenney wrote:
> > On Mon, Jun 16, 2008 at 07:01:54AM +0400, Alexey Dobriyan wrote:
> > > On Sun, Jun 15, 2008 at 04:38:24PM -0700, Linus Torvalds wrote:
> > > > On Sun, 15 Jun 2008, Paul E. McKenney wrote:
> > > > >
> > > > > If that is the right thing to do.  I would feel better about it if I
> > > > > could reproduce the failure.
> > > > 
> > > > Is there some configuration thing that might make it happen for Alexey but 
> > > > not for you? The only obvious one is the normal PREEMPT thing, but 
> > > > PREEMPT_RCU obviously depends on that, so there must be something else.
> > > > 
> > > > CONFIG_SMP? CONFIG_NO_HZ? CONFIG_[RT|FAIR]_GROUP_SCHED? There's a number 
> > > > of config options that change scheduling details..
> > > 
> > > The only way I can "fix" rcutorture here is SMP=n (not maxcpus=1!).
> > 
> > I am running SMP=y without seeing the problem.
> > 
> > > Among things tried and do not matter are NO_HZ, HIGH_RES_TIMERS, turning off
> > > debugging options (one by one and in bulk), DEBUG_PER_CPU_MAPS, HZ tweaks,
> > > SCHED_MC.
> > > 
> > > All of this doesn't help, but SMP=n does.
> > 
> > Attached is the compressed config file I used for a run on a POWER
> > machine.  I have used similar config files for x86.  For this run, I built
> > LTP, installed it, started rcutorture, ran LTP, then ended rcutorture.
> > 
> > The only other thing I can think of is that Alexey's machines are
> > somehow managing to nest NMIs or something.  I can produce a fix for
> > that, but have no way of testing it.
> 
> No NMIs here according to /proc/interrupts .
> 
>            CPU0       CPU1       
>   0:         42          0   IO-APIC-edge      timer
>   1:          8          0   IO-APIC-edge      i8042
>   8:          1          0   IO-APIC-edge      rtc
>   9:          0          0   IO-APIC-fasteoi   acpi
>  16:          0          0   IO-APIC-fasteoi   ahci, uhci_hcd:usb1
>  17:         35          0   IO-APIC-fasteoi   pata_jmicron, uhci_hcd:usb2
>  18:          0          0   IO-APIC-fasteoi   ehci_hcd:usb3, uhci_hcd:usb6
>  19:       6238          0   IO-APIC-fasteoi   ata_piix, ata_piix, uhci_hcd:usb5
>  22:        278          0   IO-APIC-fasteoi   HDA Intel
>  23:       2802          0   IO-APIC-fasteoi   uhci_hcd:usb4, ehci_hcd:usb7, eth1
> 319:       5126          0   PCI-MSI-edge      eth0
> NMI:          0          0   Non-maskable interrupts
> LOC:      66777      66036   Local timer interrupts
> RES:       3031       3403   Rescheduling interrupts
> CAL:         17         62   function call interrupts
> TLB:        671        900   TLB shootdowns
> TRM:          0          0   Thermal event interrupts
> THR:          0          0   Threshold APIC interrupts
> SPU:          0          0   Spurious interrupts
> ERR:          0

OK, thank you for the information.  Looking elsewhere...

						Thanx, Paul
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