From: Thomas Gleixner <tglx@linutronix.de>
To: Darren Hart <dvhltc@us.ibm.com>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>,
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, 22 Jul 2010 20:38:35 +0200 (CEST) [thread overview]
Message-ID: <alpine.LFD.2.00.1007222028420.2616@localhost.localdomain> (raw)
In-Reply-To: <4C488CCD.60004@us.ibm.com>
On Thu, 22 Jul 2010, Darren Hart wrote:
> Also of interest is that this path
> cpu_idle()->cpu_die()->pseries_mach_cpu_die() to start_secondary()
> enters with a preempt_count=1 if it wasn't corrupted across the hcall.
That triggers the problem as well. preempt_count needs to be 0 when
entering start_secondary(). So I really wonder how that ever worked.
> The early boot path from _start however appears to call
> start_secondary() with a preempt_count of 0.
Which is correct.
> The following patch is most certainly not correct, but it does eliminate
It is correct, but i think it is incomplete as other portions of the
thread_info on the stack might be in some weird state as well.
> the situation on mainline 100% of the time (there is still a 25%
> reproduction rate on PREEMPT_RT).
But those are diffferent issues, for which we have reasonable
explanations and patches/workarounds.
> 2) Should we call preempt_enable() in cpu_idle() prior to cpu_die() ?
No
Thanks,
tglx
next prev parent reply other threads:[~2010-07-22 18:56 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 [this message]
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
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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