mm/fault, arch: Use pagefault_disable() to check for disabled pagefaults in the handler
authorDavid Hildenbrand <dahi@linux.vnet.ibm.com>
Mon, 11 May 2015 15:52:11 +0000 (17:52 +0200)
committerIngo Molnar <mingo@kernel.org>
Tue, 19 May 2015 06:39:15 +0000 (08:39 +0200)
commit70ffdb9393a7264a069265edded729078dcf0425
tree9f93a018845ab2b02be1ee7cba83ae77f5191022
parentce01948eb85da733558fa77c2a554144a57ab0fb
mm/fault, arch: Use pagefault_disable() to check for disabled pagefaults in the handler

Introduce faulthandler_disabled() and use it to check for irq context and
disabled pagefaults (via pagefault_disable()) in the pagefault handlers.

Please note that we keep the in_atomic() checks in place - to detect
whether in irq context (in which case preemption is always properly
disabled).

In contrast, preempt_disable() should never be used to disable pagefaults.
With !CONFIG_PREEMPT_COUNT, preempt_disable() doesn't modify the preempt
counter, and therefore the result of in_atomic() differs.
We validate that condition by using might_fault() checks when calling
might_sleep().

Therefore, add a comment to faulthandler_disabled(), describing why this
is needed.

faulthandler_disabled() and pagefault_disable() are defined in
linux/uaccess.h, so let's properly add that include to all relevant files.

This patch is based on a patch from Thomas Gleixner.

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/1431359540-32227-7-git-send-email-dahi@linux.vnet.ibm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
30 files changed:
arch/alpha/mm/fault.c
arch/arc/mm/fault.c
arch/arm/mm/fault.c
arch/arm64/mm/fault.c
arch/avr32/mm/fault.c
arch/cris/mm/fault.c
arch/frv/mm/fault.c
arch/ia64/mm/fault.c
arch/m32r/mm/fault.c
arch/m68k/mm/fault.c
arch/metag/mm/fault.c
arch/microblaze/mm/fault.c
arch/mips/mm/fault.c
arch/mn10300/mm/fault.c
arch/nios2/mm/fault.c
arch/parisc/kernel/traps.c
arch/parisc/mm/fault.c
arch/powerpc/mm/fault.c
arch/s390/mm/fault.c
arch/score/mm/fault.c
arch/sh/mm/fault.c
arch/sparc/mm/fault_32.c
arch/sparc/mm/fault_64.c
arch/sparc/mm/init_64.c
arch/tile/mm/fault.c
arch/um/kernel/trap.c
arch/unicore32/mm/fault.c
arch/x86/mm/fault.c
arch/xtensa/mm/fault.c
include/linux/uaccess.h