• Tejun Heo's avatar
    percpu_ref: decouple switching to percpu mode and reinit · f47ad457
    Tejun Heo authored
    percpu_ref has treated the dropping of the base reference and
    switching to atomic mode as an integral operation; however, there's
    nothing inherent tying the two together.
    
    The use cases for percpu_ref have been expanding continuously.  While
    the current init/kill/reinit/exit model can cover a lot, the coupling
    of kill/reinit with atomic/percpu mode switching is turning out to be
    too restrictive for use cases where many percpu_refs are created and
    destroyed back-to-back with only some of them reaching extended
    operation.  The coupling also makes implementing always-atomic debug
    mode difficult.
    
    This patch separates out percpu mode switching into
    percpu_ref_switch_to_percpu() and reimplements percpu_ref_reinit() on
    top of it.
    
    * DEAD still requires ATOMIC.  A dead ref can't be switched to percpu
      mode w/o going through reinit.
    
    v2: __percpu_ref_switch_to_percpu() was missing static.  Fixed.
        Reported by Fengguang aka kbuild test robot.
    Signed-off-by: default avatarTejun Heo <tj@kernel.org>
    Reviewed-by: default avatarKent Overstreet <kmo@daterainc.com>
    Cc: Jens Axboe <axboe@kernel.dk>
    Cc: Christoph Hellwig <hch@infradead.org>
    Cc: Johannes Weiner <hannes@cmpxchg.org>
    Cc: kbuild test robot <fengguang.wu@intel.com>
    f47ad457
percpu-refcount.h 7.48 KB