From 8222dbe21e79338de92d5e1956cd1e3994cc9f93 Mon Sep 17 00:00:00 2001 From: David Hildenbrand Date: Mon, 11 May 2015 17:52:20 +0200 Subject: [PATCH] sched/preempt, mm/fault: Decouple preemption from the page fault logic 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 Signed-off-by: David Hildenbrand Signed-off-by: Peter Zijlstra (Intel) Cc: David.Laight@ACULAB.COM Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner 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 --- include/linux/uaccess.h | 16 ++-------------- 1 file changed, 2 insertions(+), 14 deletions(-) diff --git a/include/linux/uaccess.h b/include/linux/uaccess.h index 90786d2d74e51a..ae572c1386073c 100644 --- a/include/linux/uaccess.h +++ b/include/linux/uaccess.h @@ -1,7 +1,6 @@ #ifndef __LINUX_UACCESS_H__ #define __LINUX_UACCESS_H__ -#include #include #include @@ -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 } /*