[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-Id: <20150506150158.0a927470007e8ea5f3278956@linux-foundation.org>
Date: Wed, 6 May 2015 15:01:58 -0700
From: Andrew Morton <akpm@...ux-foundation.org>
To: David Hildenbrand <dahi@...ux.vnet.ibm.com>
Cc: linux-kernel@...r.kernel.org, mingo@...hat.com,
peterz@...radead.org, yang.shi@...driver.com,
bigeasy@...utronix.de, benh@...nel.crashing.org, paulus@...ba.org,
heiko.carstens@...ibm.com, schwidefsky@...ibm.com,
borntraeger@...ibm.com, mst@...hat.com, tglx@...utronix.de,
David.Laight@...LAB.COM, hughd@...gle.com, hocko@...e.cz,
ralf@...ux-mips.org, herbert@...dor.apana.org.au,
linux@....linux.org.uk, airlied@...ux.ie, daniel.vetter@...el.com,
linux-mm@...ck.org, linux-arch@...r.kernel.org
Subject: Re: [PATCH RFC 00/15] decouple pagefault_disable() from
preempt_disable()
On Wed, 6 May 2015 19:50:24 +0200 David Hildenbrand <dahi@...ux.vnet.ibm.com> wrote:
> As Peter asked me to also do the decoupling in one shot, this is
> the new series.
>
> I recently discovered that might_fault() doesn't call might_sleep()
> anymore. Therefore bugs like:
>
> spin_lock(&lock);
> rc = copy_to_user(...);
> spin_unlock(&lock);
>
> would not be detected with CONFIG_DEBUG_ATOMIC_SLEEP. The code was
> changed to disable false positives for code like:
>
> pagefault_disable();
> rc = copy_to_user(...);
> pagefault_enable();
>
> Whereby the caller wants do deal with failures.
hm, that was a significant screwup. I wonder how many bugs we
subsequently added.
>
> ..
>
> This series therefore does 2 things:
>
>
> 1. Decouple pagefault_disable() from preempt_enable()
>
> ...
>
> 2. Reenable might_sleep() checks for might_fault()
All seems sensible to me. pagefault_disabled has to go into the
task_struct (rather than being per-cpu) because
pagefault_disabled_inc() doesn't disable preemption, yes?
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
Powered by blists - more mailing lists