Re: [PATCH] multithreaded coredumps for elf exeecutables

[Mark Gross <mgross@unix-os.sc.intel.com>]

Yes.  

Patch the 2.4.17 kernel with the patch that Vamsi sent out and you're good to 
go on ia32.  I've had very good luck with this patch unit tested  on 1,2, and 
4 way ia32 systems without any failures.

However; I'm currently working on a bug fix to my process pausing 
implementation and Itanium support for it as a patch off the 2.4.17 base 
kernel.  This bug showed up on Itanium, and could bite ia32 users even though 
we haven't seen it on ia32 yet.    

I should have the bug fix patch and the Itainium patch posted next week.

Take the current 2.4.17 patch and give it a try.

--mgross

On Friday 29 March 2002 12:43 am, Jeff Jenkins wrote:
> So, after all this discussion, is there a set of source that I can use to
> build a kernel that will
> dump ALL threads to a core file?
>
> I recall that Vamsi initially send out the diffs that were to be used as a
> patch.  This sparked the issue raised by Daniel.
>
> Vamsi:  do you have a set of patches that differ than the original patch
> you sent?
>
> Thanks!
>
> -- jrj
>
> -----Original Message-----
> From: Suparna Bhattacharya [mailto:bsuparna@in.ibm.com]
> Sent: Thursday, March 21, 2002 10:06 PM
> To: mgross@unix-os.sc.intel.com
> Cc: Alan Cox; Alan Cox; asit.k.mallick@intel.com; bharata@linux.ibm.com;
> Daniel Jacobowitz; david.p.howell@intel.com; hanharat@us.ibm.com;
> jefreyr@pacbell.net; linux-kernel@vger.kernel.org;
> marcelo@conectiva.com.br; Pavel Machek; Richard_J_Moore/UK/IBM%IBMGB; S
> Vamsikrishna; sunil.saxena@intel.com; tachino@jp.fujitsu.com;
> tony.luck@intel.com; vamsi@linux.ibm.com
> Subject: Re: [PATCH] multithreaded coredumps for elf exeecutables
> Importance: High
>
>
>
> IIRC there was an observation that spin_lock_irq seems to first disable
> interrupts and then start spinning on the lock, which is why such a
> situation could arise (even though the code in schedule doesn't appear to
> explicitly disable interrupts).
>
> However, in Mark's implementation, its only the first IPI that happens
> under the runqueue lock, and that actually doesn't wait for the other CPUs
> to receive the IPI. (The purpose of the first IPI was more a matter of
> trying to improve accuracy by notifying the other threads as soon as
> possible). So there shouldn't be a deadlock. The synchronization/wait
> happens in the case of the second IPI (i.e. the smp_call_function), and by
> that time the runqueue lock has been released, and cpus_allowed has been
> updated.
>
> Regards
> Suparna
>
>   Suparna Bhattacharya
>   Linux Technology Center
>   IBM Software Lab, India
>   E-mail : bsuparna@in.ibm.com
>   Phone :  91-80-5044961
>
>
>
>
>                     Mark Gross
>                     <mgross@unix-os.sc.       To:     Alan Cox
> <alan@lxorguk.ukuu.org.uk>
>                     intel.com>                cc:
> alan@lxorguk.ukuu.org.uk (Alan Cox),
>                                                dan@debian.org (Daniel
> Jacobowitz),
>                     03/21/02 08:29 PM          vamsi@linux.ibm.com,
> pavel@suse.cz (Pavel
>                     Please respond to          Machek),
> linux-kernel@vger.kernel.org,
>                     mgross                     marcelo@conectiva.com.br,
>                                                tachino@jp.fujitsu.com,
> jefreyr@pacbell.net,
>                                                S
> Vamsikrishna/India/IBM@IBMIN, Richard J
>                                                Moore/UK/IBM@IBMGB,
> hanharat@us.ibm.com,
>                                                Suparna
> Bhattacharya/India/IBM@IBMIN,
>                                                bharata@linux.ibm.com,
>                                                asit.k.mallick@intel.com,
>                                                david.p.howell@intel.com,
>                                                tony.luck@intel.com,
> sunil.saxena@intel.com
>                                               Subject:     Re: [PATCH]
> multithreaded
>                                                coredumps for elf
> exeecutables
>
> On Thursday 21 March 2002 12:34 pm, Alan Cox wrote:
> > > This why I grabbed all those locks, and did the two sets of IPI's in
>
> the
>
> > > tcore patch.  Once the runqueue lock is grabbed, even if that process
>
> on
>
> > > the
> >
> > If you IPI holding a lock whats going to happen if while the IPI is going
> > across the cpus the other processor tries to grab the runqueue lock and
> > is spinning on it with interrupts off ?
>
> Then the at least 2 CPU's would quickly become dead locked on the
> synchronization IPI this patch sends at the end of the
> suspend_other_threads
> function call.
>
> Interrupts shouldn't be turned off when grabbing the runqueue lock.  Its
> also
> a bad thing if they would happen to be off while calling into to schedule.
>
>
> I think schedule was designed to be called only while interrupts are turned
>
> on.  It BUG's if "in_interrupt" to enforce this.
>
> --mgross
>
>
>
>
>
> -
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