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    Subject[PATCH v1 15/15] uaccess: decouple preemption from the pagefault logic
    Date
    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.

    Signed-off-by: David Hildenbrand <dahi@linux.vnet.ibm.com>
    ---
    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 90786d2..ae572c1 100644
    --- a/include/linux/uaccess.h
    +++ b/include/linux/uaccess.h
    @@ -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
    }

    /*
    --
    2.1.4


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