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From: Thomas Gleixner <tglx@linutronix.de>
To: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Peter Zijlstra <peterz@infradead.org>,
	"H. Peter Anvin" <hpa@zytor.com>,
	Khalid Aziz <khalid.aziz@oracle.com>,
	Ingo Molnar <mingo@kernel.org>,
	akpm@linux-foundation.org, andi.kleen@intel.com, rob@landley.net,
	viro@zeniv.linux.org.uk, oleg@redhat.com, venki@google.com,
	linux-kernel@vger.kernel.org
Subject: Re: [RFC] [PATCH] Pre-emption control for userspace
Date: Thu, 6 Mar 2014 15:04:47 +0100 (CET)	[thread overview]
Message-ID: <alpine.DEB.2.02.1403061459190.18573@ionos.tec.linutronix.de> (raw)
In-Reply-To: <87k3c7bfvn.fsf@rasmusvillemoes.dk>

On Thu, 6 Mar 2014, Rasmus Villemoes wrote:

> Peter Zijlstra <peterz@infradead.org> writes:
> 
> > On Thu, Mar 06, 2014 at 02:24:43PM +0100, Rasmus Villemoes wrote:
> >> Is it possible to implement non-sleeping versions of {get,put}_user()?
> >
> > __{get,put}_user()
> 
> Huh?
> 
> arch/x86/include/asm/uaccess.h:
> 
> /**
>  * __get_user: - Get a simple variable from user space, with less checking.
>  * @x:   Variable to store result.
>  * @ptr: Source address, in user space.
>  *
>  * Context: User context only.  This function may sleep.
> 
> What am I missing?

All these variants can sleep, as they might trip a page fault.....

If you want to access user space from a context which cant sleep you
need to use the __copy_to/from_user_inatomic variants. If the access
fails then they return -EFAULT and you need to deal with that
yourself.

Thanks,

	tglx




  parent reply	other threads:[~2014-03-06 14:05 UTC|newest]

Thread overview: 67+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-03-03 18:07 [RFC] [PATCH] Pre-emption control for userspace Khalid Aziz
2014-03-03 21:51 ` Davidlohr Bueso
2014-03-03 23:29   ` Khalid Aziz
2014-03-04 13:56 ` Oleg Nesterov
2014-03-04 17:44   ` Khalid Aziz
2014-03-04 18:38     ` Al Viro
2014-03-04 19:01       ` Khalid Aziz
2014-03-04 19:03     ` Oleg Nesterov
2014-03-04 20:14       ` Khalid Aziz
2014-03-05 14:38         ` Oleg Nesterov
2014-03-05 16:12           ` Oleg Nesterov
2014-03-05 17:10             ` Khalid Aziz
2014-03-04 21:12 ` H. Peter Anvin
2014-03-04 21:39   ` Khalid Aziz
2014-03-04 22:23     ` One Thousand Gnomes
2014-03-04 22:44       ` Khalid Aziz
2014-03-05  0:39         ` Thomas Gleixner
2014-03-05  0:51           ` Andi Kleen
2014-03-05 11:10             ` Peter Zijlstra
2014-03-05 17:29               ` Khalid Aziz
2014-03-05 19:58               ` Khalid Aziz
2014-03-06  9:57                 ` Peter Zijlstra
2014-03-06 16:08                   ` Khalid Aziz
2014-03-06 11:14                 ` Thomas Gleixner
2014-03-06 16:32                   ` Khalid Aziz
2014-03-05 14:54             ` Oleg Nesterov
2014-03-05 15:56               ` Andi Kleen
2014-03-05 16:36                 ` Oleg Nesterov
2014-03-05 17:22                   ` Khalid Aziz
2014-03-05 23:13                     ` David Lang
2014-03-05 23:48                       ` Khalid Aziz
2014-03-05 23:56                         ` H. Peter Anvin
2014-03-06  0:02                           ` Khalid Aziz
2014-03-06  0:13                             ` H. Peter Anvin
2014-03-05 23:59                         ` David Lang
2014-03-06  0:17                           ` Khalid Aziz
2014-03-06  0:36                             ` David Lang
2014-03-06  1:22                               ` Khalid Aziz
2014-03-06 14:23                                 ` David Lang
2014-03-06 12:13             ` Kevin Easton
2014-03-06 13:59               ` Peter Zijlstra
2014-03-06 22:41                 ` Andi Kleen
2014-03-06 14:25               ` David Lang
2014-03-06 16:12                 ` Khalid Aziz
2014-03-06 13:24   ` Rasmus Villemoes
2014-03-06 13:34     ` Peter Zijlstra
2014-03-06 13:45       ` Rasmus Villemoes
2014-03-06 14:02         ` Peter Zijlstra
2014-03-06 14:33           ` Thomas Gleixner
2014-03-06 14:34             ` H. Peter Anvin
2014-03-06 14:04         ` Thomas Gleixner [this message]
2014-03-25 17:17 ` [PATCH v2] " Khalid Aziz
2014-03-25 17:44   ` Andrew Morton
2014-03-25 17:56     ` Khalid Aziz
2014-03-25 18:14       ` Andrew Morton
2014-03-25 17:46   ` Oleg Nesterov
2014-03-25 17:59     ` Khalid Aziz
2014-03-25 18:20   ` Andi Kleen
2014-03-25 18:47     ` Khalid Aziz
2014-03-25 19:47       ` Andi Kleen
2014-03-25 18:59   ` Eric W. Biederman
2014-03-25 19:15     ` Khalid Aziz
2014-03-25 20:31       ` Eric W. Biederman
2014-03-25 21:37         ` Khalid Aziz
2014-03-26  6:03     ` Mike Galbraith
2014-03-25 23:01 ` [RFC] [PATCH] " Davidlohr Bueso
2014-03-25 23:29   ` Khalid Aziz

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