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    Subject[PATCH v2 03/11] locking/ww_mutex: Extract stamp comparison to __ww_mutex_stamp_after
    Date
    From: Nicolai Hähnle <Nicolai.Haehnle@amd.com>

    The function will be re-used in subsequent patches.

    Cc: Peter Zijlstra <peterz@infradead.org>
    Cc: Ingo Molnar <mingo@redhat.com>
    Cc: Maarten Lankhorst <dev@mblankhorst.nl>
    Cc: Daniel Vetter <daniel@ffwll.ch>
    Cc: Chris Wilson <chris@chris-wilson.co.uk>
    Cc: dri-devel@lists.freedesktop.org
    Signed-off-by: Nicolai Hähnle <Nicolai.Haehnle@amd.com>
    ---
    kernel/locking/mutex.c | 10 ++++++++--
    1 file changed, 8 insertions(+), 2 deletions(-)

    diff --git a/kernel/locking/mutex.c b/kernel/locking/mutex.c
    index 0afa998..200629a 100644
    --- a/kernel/locking/mutex.c
    +++ b/kernel/locking/mutex.c
    @@ -277,6 +277,13 @@ static __always_inline void ww_mutex_lock_acquired(struct ww_mutex *ww,
    ww_ctx->acquired++;
    }

    +static inline bool __sched
    +__ww_mutex_stamp_after(struct ww_acquire_ctx *a, struct ww_acquire_ctx *b)
    +{
    + return a->stamp - b->stamp <= LONG_MAX &&
    + (a->stamp != b->stamp || a > b);
    +}
    +
    /*
    * After acquiring lock with fastpath or when we lost out in contested
    * slowpath, set ctx and wake up any waiters so they can recheck.
    @@ -610,8 +617,7 @@ __ww_mutex_lock_check_stamp(struct mutex *lock, struct ww_acquire_ctx *ctx)
    if (!hold_ctx)
    return 0;

    - if (ctx->stamp - hold_ctx->stamp <= LONG_MAX &&
    - (ctx->stamp != hold_ctx->stamp || ctx > hold_ctx)) {
    + if (__ww_mutex_stamp_after(ctx, hold_ctx)) {
    #ifdef CONFIG_DEBUG_MUTEXES
    DEBUG_LOCKS_WARN_ON(ctx->contending_lock);
    ctx->contending_lock = ww;
    --
    2.7.4
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