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sched/preempt, mm/fault: Decouple preemption from the page fault logic

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As the fault handlers now all rely on the pagefault_disabled() checks
and implicit preempt_disable() calls by pagefault_disable() have been
made explicit, we can completely rely on the pagefault_disableD counter.

So let's no longer touch the preempt count when disabling/enabling
pagefaults. After a call to pagefault_disable(), pagefault_disabled()
will return true, but in_atomic() won't.

Reviewed-and-tested-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: David Hildenbrand <dahi@linux.vnet.ibm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: David.Laight@ACULAB.COM
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: airlied@linux.ie
Cc: akpm@linux-foundation.org
Cc: benh@kernel.crashing.org
Cc: bigeasy@linutronix.de
Cc: borntraeger@de.ibm.com
Cc: daniel.vetter@intel.com
Cc: heiko.carstens@de.ibm.com
Cc: herbert@gondor.apana.org.au
Cc: hocko@suse.cz
Cc: hughd@google.com
Cc: mst@redhat.com
Cc: paulus@samba.org
Cc: ralf@linux-mips.org
Cc: schwidefsky@de.ibm.com
Cc: yang.shi@windriver.com
Link: http://lkml.kernel.org/r/1431359540-32227-16-git-send-email-dahi@linux.vnet.ibm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
David Hildenbrand 2015-05-11 17:52:20 +02:00 committed by Ingo Molnar
parent 76deabd186
commit 8222dbe21e
1 changed files with 2 additions and 14 deletions
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16
include/linux/uaccess.h
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@ -1,7 +1,6 @@
#ifndef __LINUX_UACCESS_H__
#define __LINUX_UACCESS_H__
#include <linux/preempt.h>
#include <linux/sched.h>
#include <asm/uaccess.h>
@ -20,17 +19,11 @@ static __always_inline void pagefault_disabled_dec(void)
* These routines enable/disable the pagefault handler. If disabled, it will
* not take any locks and go straight to the fixup table.
*
* We increase the preempt and the pagefault count, to be able to distinguish
* whether we run in simple atomic context or in a real pagefault_disable()
* context.
*
* For now, after pagefault_disabled() has been called, we run in atomic
* context. User access methods will not sleep.
*
* User access methods will not sleep when called from a pagefault_disabled()
* environment.
*/
static inline void pagefault_disable(void)
{
preempt_count_inc();
pagefault_disabled_inc();
/*
* make sure to have issued the store before a pagefault
@ -47,11 +40,6 @@ static inline void pagefault_enable(void)
*/
barrier();
pagefault_disabled_dec();
#ifndef CONFIG_PREEMPT
preempt_count_dec();
#else
preempt_enable();
#endif
}
/*