From: Thomas Gleixner <tglx@linutronix.de>
To: Vaidyanathan Srinivasan <svaidy@linux.vnet.ibm.com>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>,
Darren Hart <dvhltc@us.ibm.com>,
Gautham R Shenoy <ego@in.ibm.com>,
Steven Rostedt <rostedt@goodmis.org>,
linuxppc-dev@ozlabs.org, Will Schmidt <willschm@us.ibm.com>,
Paul Mackerras <paulus@samba.org>
Subject: Re: [PATCH][RFC] preempt_count corruption across H_CEDE call with CONFIG_PREEMPT on pseries
Date: Thu, 5 Aug 2010 14:26:50 +0200 (CEST) [thread overview]
Message-ID: <alpine.LFD.2.00.1008051424130.3225@localhost.localdomain> (raw)
In-Reply-To: <20100805110625.GG3282@dirshya.in.ibm.com>
On Thu, 5 Aug 2010, Vaidyanathan Srinivasan wrote:
> * Darren Hart <dvhltc@us.ibm.com> [2010-08-04 21:45:51]:
>
> > On 07/23/2010 12:07 AM, Vaidyanathan Srinivasan wrote:
> > >* Benjamin Herrenschmidt<benh@kernel.crashing.org> [2010-07-23 15:11:00]:
> > >
> > >>On Fri, 2010-07-23 at 10:38 +0530, Vaidyanathan Srinivasan wrote:
> > >>>Yes. extended_cede_processor() will return with interrupts enabled in
> > >>>the cpu. (This is done by the hypervisor). Under normal cases we
> > >>>cannot be interrupted because no IO interrupts are routed to us after
> > >>>xics_teardown_cpu() and since the CPU is out of the map, nobody will
> > >>>send us IPIs.
> > >>
> > >>What about decrementer ?
> > >
> > >Decrementer expiry event handling is bit complex. The event as such
> > >may not bring back the extended_cede_processor() cpu, but may be
> > >marked pending when we get out of this state eventually. I will find
> > >more information on this event and update.
> >
> > Hi Vaidy, have you been able to dig anything up about the
> > decrementer expiry?
>
> Hi Darren,
>
> Yes, it is possible that the cpu in extended_cede_processor() can be
> woken up by the decrementer. But the expectation is that we will
> return back to this context since we will not have any pending timers.
The problem is that you might get woken _before_ the timers have been
migrated away.
> Our stack should not change even if we get the decrementer interrupts.
But you should not execute kernel code when you got offlined either.
Thanks,
tglx
next prev parent reply other threads:[~2010-08-05 12:29 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-07-22 18:24 [PATCH][RFC] preempt_count corruption across H_CEDE call with CONFIG_PREEMPT on pseries Darren Hart
2010-07-22 18:36 ` Darren Hart
2010-07-22 18:38 ` Thomas Gleixner
2010-08-10 22:36 ` Darren Hart
2010-07-22 22:25 ` Benjamin Herrenschmidt
2010-07-22 23:57 ` Darren Hart
2010-07-23 4:44 ` Darren Hart
2010-07-23 5:08 ` Vaidyanathan Srinivasan
2010-07-23 5:11 ` Benjamin Herrenschmidt
2010-07-23 7:07 ` Vaidyanathan Srinivasan
2010-08-05 4:45 ` Darren Hart
2010-08-05 11:06 ` Vaidyanathan Srinivasan
2010-08-05 12:26 ` Thomas Gleixner [this message]
2010-07-23 5:09 ` Benjamin Herrenschmidt
2010-08-06 2:19 ` Darren Hart
2010-08-06 5:09 ` Vaidyanathan Srinivasan
2010-08-06 7:13 ` Darren Hart
2010-07-23 14:39 ` Will Schmidt
2010-08-04 13:44 ` Darren Hart
2010-08-19 15:58 ` Ankita Garg
2010-08-19 18:58 ` Will Schmidt
2010-08-23 22:20 ` Darren Hart
2010-08-31 7:12 ` Darren Hart
2010-09-01 5:54 ` Michael Ellerman
2010-09-01 15:10 ` Darren Hart
2010-09-01 18:47 ` Darren Hart
2010-09-01 19:59 ` Steven Rostedt
2010-09-01 20:42 ` Darren Hart
2010-09-02 1:02 ` Michael Neuling
2010-09-02 4:06 ` Steven Rostedt
2010-09-02 6:04 ` Darren Hart
2010-09-03 20:10 ` Will Schmidt
2010-09-02 23:04 ` Michael Neuling
2010-09-03 0:08 ` Darren Hart
2010-09-02 3:46 ` Michael Neuling
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