From: Valentine <vbarshak@ru•mvista.com>
To: Benjamin Herrenschmidt <benh@kernel•crashing.org>
Cc: olof@lixom•net, linuxppc-dev@ozlabs•org, paulus@samba•org
Subject: Re: [PATCH v3] powerpc/ppc64: Use preempt_schedule_irq instead of preempt_schedule
Date: Thu, 29 Oct 2009 01:49:57 +0300 [thread overview]
Message-ID: <4AE8CA95.7060402@ru.mvista.com> (raw)
In-Reply-To: <1256765834.26770.6.camel@pasglop>
Benjamin Herrenschmidt wrote:
> On Thu, 2009-10-29 at 00:28 +0300, Valentine wrote:
>> Benjamin Herrenschmidt wrote:
>>> On Wed, 2009-10-28 at 22:19 +0300, Valentine wrote:
>>>
>>>> I'm just not sure that we need to clear HARDIRQEN here, since we don't
>>>> really hard-disable the the interrupts.
>>> We do, or rather, we come in with the interrupts hard disabled, no ?
>> Yes, looks like the interrupts are disabled at this point (before
>> preempt_schedule_irq) most of the times, but we don't hard-disable them
>> here. We just soft-disable them to make preempt_schedule_irq happy. Even
>> if an interrupt fires, it will be hard-disabled and the hardirq flag
>> will be cleared by the exception handler right away. I just think that
>> there's no need to clear hardirq flag if we don't clear MSR_EE.
>
> My point is that MSR_EE _is_ already clear... isn't it ?
Yes, the MSR_EE is cleared before we jump to do_work. I'm OK with
clearing the hardirqenable flag. I just assumed that the hardirq flag
was supposed to reflect the MSR_EE state, so it looked a bit odd
clearing the MSR_EE at one place and then reflecting the change at another.
Anyway, the patch works fine.
Thanks,
Val.
So either we
> set it back, or we clear HARDIRQEN to reflect it. It will be re-enable
> as soon as preempt_schedule_irq() calls local_irq_enable() which is soon
> enough anyways.
>
> Also that avoids perf interrupt sneaking in since those act as NMIs in
> that regard and -will- get in even when soft disabled.
>
> Cheers,
> Ben.
>
>> Thanks,
>> Val.
>>> Ben.
>>>
>>>> Thanks,
>>>> Val.
>>>>
>>>>> + TRACE_DISABLE_INTS
>>>>> +
>>>>> + /* Call the scheduler with soft IRQs off */
>>>>> +1: bl .preempt_schedule_irq
>>>>> +
>>>>> + /* Hard-disable interrupts again (and update PACA) */
>>>>> #ifdef CONFIG_PPC_BOOK3E
>>>>> - wrteei 1
>>>>> - bl .preempt_schedule
>>>>> wrteei 0
>>>>> #else
>>>>> - ori r10,r10,MSR_EE
>>>>> - mtmsrd r10,1 /* reenable interrupts */
>>>>> - bl .preempt_schedule
>>>>> mfmsr r10
>>>>> - clrrdi r9,r1,THREAD_SHIFT
>>>>> - rldicl r10,r10,48,1 /* disable interrupts again */
>>>>> + rldicl r10,r10,48,1
>>>>> rotldi r10,r10,16
>>>>> mtmsrd r10,1
>>>>> #endif /* CONFIG_PPC_BOOK3E */
>>>>> + li r0,0
>>>>> + stb r0,PACAHARDIRQEN(r13)
>>>>> +
>>>>> + /* Re-test flags and eventually loop */
>>>>> + clrrdi r9,r1,THREAD_SHIFT
>>>>> ld r4,TI_FLAGS(r9)
>>>>> andi. r0,r4,_TIF_NEED_RESCHED
>>>>> bne 1b
>>>>> b restore
>>>>>
>>>>> user_work:
>>>>> -#endif
>>>>> +#endif /* CONFIG_PREEMPT */
>>>>> +
>>>>> /* Enable interrupts */
>>>>> #ifdef CONFIG_PPC_BOOK3E
>>>>> wrteei 1
>>>
>
>
next prev parent reply other threads:[~2009-10-28 22:49 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-10-19 18:28 [PATCH] [RFC] PowerPC64: Use preempt_schedule_irq instead of preempt_schedule when returning from exceptions Valentine Barshak
2009-10-26 23:55 ` Benjamin Herrenschmidt
2009-10-27 5:41 ` [PATCH v3] powerpc/ppc64: Use preempt_schedule_irq instead of preempt_schedule Benjamin Herrenschmidt
2009-10-28 19:19 ` Valentine
2009-10-28 20:30 ` Benjamin Herrenschmidt
2009-10-28 21:28 ` Valentine
2009-10-28 21:37 ` Benjamin Herrenschmidt
2009-10-28 22:49 ` Valentine [this message]
2009-10-29 0:49 ` Benjamin Herrenschmidt
2009-11-06 22:38 ` Valentine
2009-11-06 22:49 ` Benjamin Herrenschmidt
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=4AE8CA95.7060402@ru.mvista.com \
--to=vbarshak@ru$(echo .)mvista.com \
--cc=benh@kernel$(echo .)crashing.org \
--cc=linuxppc-dev@ozlabs$(echo .)org \
--cc=olof@lixom$(echo .)net \
--cc=paulus@samba$(echo .)org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox