• Peter Zijlstra's avatar
    atomic/tty: Fix up atomic abuse in ldsem · 5fd691af
    Peter Zijlstra authored
    Mark found ldsem_cmpxchg() needed an (atomic_long_t *) cast to keep
    working after making the atomic_long interface type safe.
    
    Needing casts is bad form, which made me look at the code. There are no
    ld_semaphore::count users outside of these functions so there is no
    reason why it can not be an atomic_long_t in the first place, obviating
    the need for this cast.
    
    That also ensures the loads use atomic_long_read(), which implies (at
    least) READ_ONCE() in order to guarantee single-copy-atomic loads.
    
    When using atomic_long_try_cmpxchg() the ldsem_cmpxchg() wrapper gets
    very thin (the only difference is not changing *old on success, which
    most callers don't seem to care about).
    
    So rework the whole thing to use atomic_long_t and its accessors
    directly.
    
    While there, fixup all the horrible comment styles.
    
    Cc: Peter Hurley <peter@hurleysoftware.com>
    Reported-by: default avatarMark Rutland <mark.rutland@arm.com>
    Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
    Acked-by: default avatarMark Rutland <mark.rutland@arm.com>
    Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
    5fd691af
tty_ldsem.c 10.8 KB