From: David Hildenbrand <dahi@linux.vnet.ibm.com>
To: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: linux-arch@vger.kernel.org, "Michael S. Tsirkin" <mst@redhat.com>,
linux-kernel@vger.kernel.org,
Christian Borntraeger <borntraeger@de.ibm.com>,
paulus@samba.org, schwidefsky@de.ibm.com,
akpm@linux-foundation.org, linuxppc-dev@lists.ozlabs.org,
mingo@kernel.org
Subject: Re: [RFC 0/2] Reenable might_sleep() checks for might_fault() when atomic
Date: Thu, 27 Nov 2014 13:08:03 +0100 [thread overview]
Message-ID: <20141127130803.7cfbe5aa@thinkpad-w530> (raw)
In-Reply-To: <20141127120441.GB4390@osiris>
> On Thu, Nov 27, 2014 at 09:03:01AM +0100, David Hildenbrand wrote:
> > > Code like
> > > spin_lock(&lock);
> > > if (copy_to_user(...))
> > > rc = ...
> > > spin_unlock(&lock);
> > > really *should* generate warnings like it did before.
> > >
> > > And *only* code like
> > > spin_lock(&lock);
> >
> > Is only code like this valid or also with the spin_lock() dropped?
> > (e.g. the access in patch1 if I remember correctly)
> >
> > So should page_fault_disable() increment the pagefault counter and the preempt
> > counter or only the first one?
>
> Given that a sequence like
>
> page_fault_disable();
> if (copy_to_user(...))
> rc = ...
> page_fault_enable();
>
> is correct code right now I think page_fault_disable() should increase both.
> No need for surprising semantic changes.
>
> > So we would have pagefault code rely on:
> >
> > in_disabled_pagefault() ( pagefault_disabled() ... whatever ) instead of
> > in_atomic().
>
> No, let's be more defensive: the page fault handler should do nothing if
> in_atomic() just like now. But it could have a quick check and emit a one
> time warning if page faults aren't disabled in addition.
> That might help debugging but keeps the system more likely alive.
Sounds sane if we increase both counters!
>
> might_fault() however should call might_sleep() if page faults aren't
> disabled, but that's what you proposed anyway I think.
Jap, sounds good to me. Will see if I can come up with something.
Thanks!
next prev parent reply other threads:[~2014-11-27 12:08 UTC|newest]
Thread overview: 44+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-11-25 11:43 [RFC 0/2] Reenable might_sleep() checks for might_fault() when atomic David Hildenbrand
2014-11-25 11:43 ` [RFC 1/2] powerpc/fsl-pci: atomic get_user when pagefault_disabled David Hildenbrand
2015-01-30 5:15 ` [RFC,1/2] " Scott Wood
2015-01-30 7:58 ` David Hildenbrand
2014-11-25 11:43 ` [RFC 2/2] mm, sched: trigger might_sleep() in might_fault() when atomic David Hildenbrand
2014-11-26 7:02 ` [RFC 0/2] Reenable might_sleep() checks for " Michael S. Tsirkin
2014-11-26 10:05 ` David Hildenbrand
2014-11-26 15:17 ` Michael S. Tsirkin
2014-11-26 15:23 ` Michael S. Tsirkin
2014-11-26 15:32 ` David Hildenbrand
2014-11-26 15:47 ` Michael S. Tsirkin
2014-11-26 16:02 ` David Hildenbrand
2014-11-26 16:19 ` Michael S. Tsirkin
2014-11-26 16:30 ` Christian Borntraeger
2014-11-26 16:50 ` Michael S. Tsirkin
2014-11-26 16:07 ` Christian Borntraeger
2014-11-26 16:32 ` Michael S. Tsirkin
2014-11-26 16:51 ` Christian Borntraeger
2014-11-26 17:04 ` Michael S. Tsirkin
2014-11-26 17:21 ` Michael S. Tsirkin
2014-11-27 7:09 ` Heiko Carstens
2014-11-27 7:40 ` Michael S. Tsirkin
2014-11-27 8:03 ` David Hildenbrand
2014-11-27 12:04 ` Heiko Carstens
2014-11-27 12:08 ` David Hildenbrand [this message]
2014-11-27 15:07 ` Thomas Gleixner
2014-11-27 15:19 ` David Hildenbrand
2014-11-27 15:37 ` David Laight
2014-11-27 15:45 ` David Hildenbrand
2014-11-27 16:27 ` David Laight
2014-11-27 16:49 ` David Hildenbrand
2014-11-27 21:52 ` Thomas Gleixner
2014-11-28 7:34 ` David Hildenbrand
2014-11-26 15:30 ` Christian Borntraeger
2014-11-26 15:37 ` Michael S. Tsirkin
2014-11-26 16:02 ` Christian Borntraeger
2014-11-26 15:22 ` Michael S. Tsirkin
2014-11-27 17:10 ` [PATCH RFC " David Hildenbrand
2014-11-27 17:10 ` [PATCH RFC 1/2] preempt: track pagefault_disable() calls in the preempt counter David Hildenbrand
2014-11-27 17:10 ` [PATCH RFC 2/2] mm, sched: trigger might_sleep() in might_fault() when pagefaults are disabled David Hildenbrand
2014-11-27 17:24 ` Michael S. Tsirkin
2014-11-27 17:32 ` Michael S. Tsirkin
2014-11-27 18:08 ` David Hildenbrand
2014-11-27 18:27 ` Michael S. Tsirkin
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