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From: Sven Schnelle <svens@stackframe.org>
To: John David Anglin <dave.anglin@bell.net>
Cc: Helge Deller <deller@gmx.de>,
	linux-parisc <linux-parisc@vger.kernel.org>
Subject: Re: [PATCH] parisc: Don't disable interrupts in cmpxchg and futex operations
Date: Wed, 20 Oct 2021 21:05:40 +0200	[thread overview]
Message-ID: <877de734aj.fsf@x1.stackframe.org> (raw)
In-Reply-To: <e8a1f0c9-2af2-baa5-a252-4abbc8d28373@bell.net> (John David Anglin's message of "Wed, 20 Oct 2021 14:32:55 -0400")

John David Anglin <dave.anglin@bell.net> writes:

> On 2021-10-17 12:30 p.m., Helge Deller wrote:
>> It seems the warnings are gone if I remove the irq masking.
>> I see the options:
>> a) revert the irq masking in syscall.S. Not sure if it really hurts performance.
>> b) revert the patch from Sven.
>> c) insert code to turn back irq on in the fault handler if we are on the gateway page.
>> What is your thought?
>
> After some thought, I believe option a) is the best.  I no longer think interrupts can be
> disabled in the futex and cmpxchg operations because of COW breaks.  This not ideal but
> I suspect it's the best we can do.
>
> For the cmpxchg operations in syscall.S, we rely on the code to not schedule off the gateway
> page.  For the futex, I added code to disable preemption.
>
> So far, I haven't seen the warnings with the attached change but the change is only lightly tested.

Thanks Dave. I just applied it to my tree and will give it a spin.

  reply	other threads:[~2021-10-20 19:05 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-10-15 19:56 [PATCH] parisc: don't enable irqs unconditionally in handle_interruption() Sven Schnelle
     [not found] ` <969e8f20-d27c-77cd-62c1-ddb86213ddec@gmx.de>
     [not found]   ` <a5030b48-b6bc-639c-5360-0389103c228e@bell.net>
     [not found]     ` <ac539330-bdc2-1bba-e2c2-78d29614864f@bell.net>
     [not found]       ` <8bef26c2-daee-2a6c-1828-100a5b27e205@gmx.de>
     [not found]         ` <28325394-99de-67f4-dcca-b1caf1105df2@bell.net>
     [not found]           ` <87o87oxhhf.fsf@x1.stackframe.org>
     [not found]             ` <48780780-0f8c-5aa9-d362-a9b9ddeaeedb@gmx.de>
2021-10-20 18:32               ` [PATCH] parisc: Don't disable interrupts in cmpxchg and futex operations John David Anglin
2021-10-20 19:05                 ` Sven Schnelle [this message]
2021-11-03 14:42                   ` [PATCH v2] " Helge Deller
2021-11-03 15:41                     ` John David Anglin
2021-11-03 17:10                     ` Sven Schnelle

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