• Mark Rutland's avatar
    locking/atomics: Rework ordering barriers · fd2efaa4
    Mark Rutland authored
    Currently architectures can override __atomic_op_*() to define the barriers
    used before/after a relaxed atomic when used to build acquire/release/fence
    variants.
    
    This has the unfortunate property of requiring the architecture to define the
    full wrapper for the atomics, rather than just the barriers they care about,
    and gets in the way of generating atomics which can be easily read.
    
    Instead, this patch has architectures define an optional set of barriers:
    
    * __atomic_acquire_fence()
    * __atomic_release_fence()
    * __atomic_pre_full_fence()
    * __atomic_post_full_fence()
    
    ... which <linux/atomic.h> uses to build the wrappers.
    
    It would be nice if we could undef these, along with the __atomic_op_*()
    wrappers, but that would break the cmpxchg() wrappers, which are written
    in preprocessor. Undefs would have been nice, but alas.
    
    There should be no functional change as a result of this patch.
    Signed-off-by: default avatarMark Rutland <mark.rutland@arm.com>
    Acked-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
    Acked-by: default avatarWill Deacon <will.deacon@arm.com>
    Cc: Andrea Parri <parri.andrea@gmail.com>
    Cc: Boqun Feng <boqun.feng@gmail.com>
    Cc: Linus Torvalds <torvalds@linux-foundation.org>
    Cc: Peter Zijlstra <peterz@infradead.org>
    Cc: Thomas Gleixner <tglx@linutronix.de>
    Cc: andy.shevchenko@gmail.com
    Cc: arnd@arndb.de
    Cc: aryabinin@virtuozzo.com
    Cc: catalin.marinas@arm.com
    Cc: dvyukov@google.com
    Cc: glider@google.com
    Cc: linux-arm-kernel@lists.infradead.org
    Cc: peter@hurleysoftware.com
    Link: http://lkml.kernel.org/r/20180716113017.3909-7-mark.rutland@arm.comSigned-off-by: default avatarIngo Molnar <mingo@kernel.org>
    fd2efaa4
atomic.h 36.8 KB