• Mark Rutland's avatar
    locking/atomics, workqueue: Convert ACCESS_ONCE() to READ_ONCE()/WRITE_ONCE() · c95491ed
    Mark Rutland authored
    
    
    For several reasons, it is desirable to use {READ,WRITE}_ONCE() in
    preference to ACCESS_ONCE(), and new code is expected to use one of the
    former. So far, there's been no reason to change most existing uses of
    ACCESS_ONCE(), as these aren't currently harmful.
    
    However, for some features it is necessary to instrument reads and
    writes separately, which is not possible with ACCESS_ONCE(). This
    distinction is critical to correct operation.
    
    It's possible to transform the bulk of kernel code using the Coccinelle
    script below. However, this doesn't handle comments, leaving references
    to ACCESS_ONCE() instances which have been removed. As a preparatory
    step, this patch converts the workqueue code and comments to use
    {READ,WRITE}_ONCE() consistently.
    
    ----
    virtual patch
    
    @ depends on patch @
    expression E1, E2;
    @@
    
    - ACCESS_ONCE(E1) = E2
    + WRITE_ONCE(E1, E2)
    
    @ depends on patch @
    expression E;
    @@
    
    - ACCESS_ONCE(E)
    + READ_ONCE(E)
    ----
    Signed-off-by: default avatarMark Rutland <mark.rutland@arm.com>
    Signed-off-by: default avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
    Acked-by: default avatarTejun Heo <tj@kernel.org>
    Cc: Lai Jiangshan <jiangshanlai@gmail.com>
    Cc: Linus Torvalds <torvalds@linux-foundation.org>
    Cc: Peter Zijlstra <peterz@infradead.org>
    Cc: Thomas Gleixner <tglx@linutronix.de>
    Cc: davem@davemloft.net
    Cc: linux-arch@vger.kernel.org
    Cc: mpe@ellerman.id.au
    Cc: shuah@kernel.org
    Cc: snitzer@redhat.com
    Cc: thor.thayer@linux.intel.com
    Cc: viro@zeniv.linux.org.uk
    Cc: will.deacon@arm.com
    Link: http://lkml.kernel.org/r/1508792849-3115-12-git-send-email-paulmck@linux.vnet.ibm.com
    
    Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
    c95491ed
workqueue.c 157 KB