• David Hildenbrand's avatar
    mm/fault, arch: Use pagefault_disable() to check for disabled pagefaults in the handler · 70ffdb93
    David Hildenbrand authored
    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: default avatarThomas Gleixner <tglx@linutronix.de>
    Signed-off-by: default avatarDavid Hildenbrand <dahi@linux.vnet.ibm.com>
    Signed-off-by: default avatarPeter 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.comSigned-off-by: default avatarIngo Molnar <mingo@kernel.org>
    70ffdb93
fault.c 8.75 KB