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	Version: linux-6.0.1 spark-3.0.0 hadoop-3.2.0-src hadoop-3.3.0-src spark-2.4.7 linux-4.15.13 hadoop-2.7.4-src Revert   Change

 /* SPDX-License-Identifier: GPL-2.0-only */
 
 #ifndef WW_RT
 
 #define MUTEX       mutex
 #define MUTEX_WAITER    mutex_waiter
 
 static inline struct mutex_waiter *
 __ww_waiter_first(struct mutex *lock)
 {
     struct mutex_waiter *w;
 
     w = list_first_entry(&lock->wait_list, struct mutex_waiter, list);
     if (list_entry_is_head(w, &lock->wait_list, list))
         return NULL;
 
     return w;
 }
 
 static inline struct mutex_waiter *
 __ww_waiter_next(struct mutex *lock, struct mutex_waiter *w)
 {
     w = list_next_entry(w, list);
     if (list_entry_is_head(w, &lock->wait_list, list))
         return NULL;
 
     return w;
 }
 
 static inline struct mutex_waiter *
 __ww_waiter_prev(struct mutex *lock, struct mutex_waiter *w)
 {
     w = list_prev_entry(w, list);
     if (list_entry_is_head(w, &lock->wait_list, list))
         return NULL;
 
     return w;
 }
 
 static inline struct mutex_waiter *
 __ww_waiter_last(struct mutex *lock)
 {
     struct mutex_waiter *w;
 
     w = list_last_entry(&lock->wait_list, struct mutex_waiter, list);
     if (list_entry_is_head(w, &lock->wait_list, list))
         return NULL;
 
     return w;
 }
 
 static inline void
 __ww_waiter_add(struct mutex *lock, struct mutex_waiter *waiter, struct mutex_waiter *pos)
 {
     struct list_head *p = &lock->wait_list;
     if (pos)
         p = &pos->list;
     __mutex_add_waiter(lock, waiter, p);
 }
 
 static inline struct task_struct *
 __ww_mutex_owner(struct mutex *lock)
 {
     return __mutex_owner(lock);
 }
 
 static inline bool
 __ww_mutex_has_waiters(struct mutex *lock)
 {
     return atomic_long_read(&lock->owner) & MUTEX_FLAG_WAITERS;
 }
 
 static inline void lock_wait_lock(struct mutex *lock)
 {
     raw_spin_lock(&lock->wait_lock);
 }
 
 static inline void unlock_wait_lock(struct mutex *lock)
 {
     raw_spin_unlock(&lock->wait_lock);
 }
 
 static inline void lockdep_assert_wait_lock_held(struct mutex *lock)
 {
     lockdep_assert_held(&lock->wait_lock);
 }
 
 #else /* WW_RT */
 
 #define MUTEX       rt_mutex
 #define MUTEX_WAITER    rt_mutex_waiter
 
 static inline struct rt_mutex_waiter *
 __ww_waiter_first(struct rt_mutex *lock)
 {
     struct rb_node *n = rb_first(&lock->rtmutex.waiters.rb_root);
     if (!n)
         return NULL;
     return rb_entry(n, struct rt_mutex_waiter, tree_entry);
 }
 
 static inline struct rt_mutex_waiter *
 __ww_waiter_next(struct rt_mutex *lock, struct rt_mutex_waiter *w)
 {
     struct rb_node *n = rb_next(&w->tree_entry);
     if (!n)
         return NULL;
     return rb_entry(n, struct rt_mutex_waiter, tree_entry);
 }
 
 static inline struct rt_mutex_waiter *
 __ww_waiter_prev(struct rt_mutex *lock, struct rt_mutex_waiter *w)
 {
     struct rb_node *n = rb_prev(&w->tree_entry);
     if (!n)
         return NULL;
     return rb_entry(n, struct rt_mutex_waiter, tree_entry);
 }
 
 static inline struct rt_mutex_waiter *
 __ww_waiter_last(struct rt_mutex *lock)
 {
     struct rb_node *n = rb_last(&lock->rtmutex.waiters.rb_root);
     if (!n)
         return NULL;
     return rb_entry(n, struct rt_mutex_waiter, tree_entry);
 }
 
 static inline void
 __ww_waiter_add(struct rt_mutex *lock, struct rt_mutex_waiter *waiter, struct rt_mutex_waiter *pos)
 {
     /* RT unconditionally adds the waiter first and then removes it on error */
 }
 
 static inline struct task_struct *
 __ww_mutex_owner(struct rt_mutex *lock)
 {
     return rt_mutex_owner(&lock->rtmutex);
 }
 
 static inline bool
 __ww_mutex_has_waiters(struct rt_mutex *lock)
 {
     return rt_mutex_has_waiters(&lock->rtmutex);
 }
 
 static inline void lock_wait_lock(struct rt_mutex *lock)
 {
     raw_spin_lock(&lock->rtmutex.wait_lock);
 }
 
 static inline void unlock_wait_lock(struct rt_mutex *lock)
 {
     raw_spin_unlock(&lock->rtmutex.wait_lock);
 }
 
 static inline void lockdep_assert_wait_lock_held(struct rt_mutex *lock)
 {
     lockdep_assert_held(&lock->rtmutex.wait_lock);
 }
 
 #endif /* WW_RT */
 
 /*
  * Wait-Die:
  *   The newer transactions are killed when:
  *     It (the new transaction) makes a request for a lock being held
  *     by an older transaction.
  *
  * Wound-Wait:
  *   The newer transactions are wounded when:
  *     An older transaction makes a request for a lock being held by
  *     the newer transaction.
  */
 
 /*
  * Associate the ww_mutex @ww with the context @ww_ctx under which we acquired
  * it.
  */
 static __always_inline void
 ww_mutex_lock_acquired(struct ww_mutex *ww, struct ww_acquire_ctx *ww_ctx)
 {
 #ifdef DEBUG_WW_MUTEXES
     /*
      * If this WARN_ON triggers, you used ww_mutex_lock to acquire,
      * but released with a normal mutex_unlock in this call.
      *
      * This should never happen, always use ww_mutex_unlock.
      */
     DEBUG_LOCKS_WARN_ON(ww->ctx);
 
     /*
      * Not quite done after calling ww_acquire_done() ?
      */
     DEBUG_LOCKS_WARN_ON(ww_ctx->done_acquire);
 
     if (ww_ctx->contending_lock) {
         /*
          * After -EDEADLK you tried to
          * acquire a different ww_mutex? Bad!
          */
         DEBUG_LOCKS_WARN_ON(ww_ctx->contending_lock != ww);
 
         /*
          * You called ww_mutex_lock after receiving -EDEADLK,
          * but 'forgot' to unlock everything else first?
          */
         DEBUG_LOCKS_WARN_ON(ww_ctx->acquired > 0);
         ww_ctx->contending_lock = NULL;
     }
 
     /*
      * Naughty, using a different class will lead to undefined behavior!
      */
     DEBUG_LOCKS_WARN_ON(ww_ctx->ww_class != ww->ww_class);
 #endif
     ww_ctx->acquired++;
     ww->ctx = ww_ctx;
 }
 
 /*
  * Determine if @a is 'less' than @b. IOW, either @a is a lower priority task
  * or, when of equal priority, a younger transaction than @b.
  *
  * Depending on the algorithm, @a will either need to wait for @b, or die.
  */
 static inline bool
 __ww_ctx_less(struct ww_acquire_ctx *a, struct ww_acquire_ctx *b)
 {
 /*
  * Can only do the RT prio for WW_RT, because task->prio isn't stable due to PI,
  * so the wait_list ordering will go wobbly. rt_mutex re-queues the waiter and
  * isn't affected by this.
  */
 #ifdef WW_RT
     /* kernel prio; less is more */
     int a_prio = a->task->prio;
     int b_prio = b->task->prio;
 
     if (rt_prio(a_prio) || rt_prio(b_prio)) {
 
         if (a_prio > b_prio)
             return true;
 
         if (a_prio < b_prio)
             return false;
 
         /* equal static prio */
 
         if (dl_prio(a_prio)) {
             if (dl_time_before(b->task->dl.deadline,
                        a->task->dl.deadline))
                 return true;
 
             if (dl_time_before(a->task->dl.deadline,
                        b->task->dl.deadline))
                 return false;
         }
 
         /* equal prio */
     }
 #endif
 
     /* FIFO order tie break -- bigger is younger */
     return (signed long)(a->stamp - b->stamp) > 0;
 }
 
 /*
  * Wait-Die; wake a lesser waiter context (when locks held) such that it can
  * die.
  *
  * Among waiters with context, only the first one can have other locks acquired
  * already (ctx->acquired > 0), because __ww_mutex_add_waiter() and
  * __ww_mutex_check_kill() wake any but the earliest context.
  */
 static bool
 __ww_mutex_die(struct MUTEX *lock, struct MUTEX_WAITER *waiter,
            struct ww_acquire_ctx *ww_ctx)
 {
     if (!ww_ctx->is_wait_die)
         return false;
 
     if (waiter->ww_ctx->acquired > 0 && __ww_ctx_less(waiter->ww_ctx, ww_ctx)) {
 #ifndef WW_RT
         debug_mutex_wake_waiter(lock, waiter);
 #endif
         wake_up_process(waiter->task);
     }
 
     return true;
 }
 
 /*
  * Wound-Wait; wound a lesser @hold_ctx if it holds the lock.
  *
  * Wound the lock holder if there are waiters with more important transactions
  * than the lock holders. Even if multiple waiters may wound the lock holder,
  * it's sufficient that only one does.
  */
 static bool __ww_mutex_wound(struct MUTEX *lock,
                  struct ww_acquire_ctx *ww_ctx,
                  struct ww_acquire_ctx *hold_ctx)
 {
     struct task_struct *owner = __ww_mutex_owner(lock);
 
     lockdep_assert_wait_lock_held(lock);
 
     /*
      * Possible through __ww_mutex_add_waiter() when we race with
      * ww_mutex_set_context_fastpath(). In that case we'll get here again
      * through __ww_mutex_check_waiters().
      */
     if (!hold_ctx)
         return false;
 
     /*
      * Can have !owner because of __mutex_unlock_slowpath(), but if owner,
      * it cannot go away because we'll have FLAG_WAITERS set and hold
      * wait_lock.
      */
     if (!owner)
         return false;
 
     if (ww_ctx->acquired > 0 && __ww_ctx_less(hold_ctx, ww_ctx)) {
         hold_ctx->wounded = 1;
 
         /*
          * wake_up_process() paired with set_current_state()
          * inserts sufficient barriers to make sure @owner either sees
          * it's wounded in __ww_mutex_check_kill() or has a
          * wakeup pending to re-read the wounded state.
          */
         if (owner != current)
             wake_up_process(owner);
 
         return true;
     }
 
     return false;
 }
 
 /*
  * We just acquired @lock under @ww_ctx, if there are more important contexts
  * waiting behind us on the wait-list, check if they need to die, or wound us.
  *
  * See __ww_mutex_add_waiter() for the list-order construction; basically the
  * list is ordered by stamp, smallest (oldest) first.
  *
  * This relies on never mixing wait-die/wound-wait on the same wait-list;
  * which is currently ensured by that being a ww_class property.
  *
  * The current task must not be on the wait list.
  */
 static void
 __ww_mutex_check_waiters(struct MUTEX *lock, struct ww_acquire_ctx *ww_ctx)
 {
     struct MUTEX_WAITER *cur;
 
     lockdep_assert_wait_lock_held(lock);
 
     for (cur = __ww_waiter_first(lock); cur;
          cur = __ww_waiter_next(lock, cur)) {
 
         if (!cur->ww_ctx)
             continue;
 
         if (__ww_mutex_die(lock, cur, ww_ctx) ||
             __ww_mutex_wound(lock, cur->ww_ctx, ww_ctx))
             break;
     }
 }
 
 /*
  * After acquiring lock with fastpath, where we do not hold wait_lock, set ctx
  * and wake up any waiters so they can recheck.
  */
 static __always_inline void
 ww_mutex_set_context_fastpath(struct ww_mutex *lock, struct ww_acquire_ctx *ctx)
 {
     ww_mutex_lock_acquired(lock, ctx);
 
     /*
      * The lock->ctx update should be visible on all cores before
      * the WAITERS check is done, otherwise contended waiters might be
      * missed. The contended waiters will either see ww_ctx == NULL
      * and keep spinning, or it will acquire wait_lock, add itself
      * to waiter list and sleep.
      */
     smp_mb(); /* See comments above and below. */
 
     /*
      * [W] ww->ctx = ctx        [W] MUTEX_FLAG_WAITERS
      *     MB               MB
      * [R] MUTEX_FLAG_WAITERS   [R] ww->ctx
      *
      * The memory barrier above pairs with the memory barrier in
      * __ww_mutex_add_waiter() and makes sure we either observe ww->ctx
      * and/or !empty list.
      */
     if (likely(!__ww_mutex_has_waiters(&lock->base)))
         return;
 
     /*
      * Uh oh, we raced in fastpath, check if any of the waiters need to
      * die or wound us.
      */
     lock_wait_lock(&lock->base);
     __ww_mutex_check_waiters(&lock->base, ctx);
     unlock_wait_lock(&lock->base);
 }
 
 static __always_inline int
 __ww_mutex_kill(struct MUTEX *lock, struct ww_acquire_ctx *ww_ctx)
 {
     if (ww_ctx->acquired > 0) {
 #ifdef DEBUG_WW_MUTEXES
         struct ww_mutex *ww;
 
         ww = container_of(lock, struct ww_mutex, base);
         DEBUG_LOCKS_WARN_ON(ww_ctx->contending_lock);
         ww_ctx->contending_lock = ww;
 #endif
         return -EDEADLK;
     }
 
     return 0;
 }
 
 /*
  * Check the wound condition for the current lock acquire.
  *
  * Wound-Wait: If we're wounded, kill ourself.
  *
  * Wait-Die: If we're trying to acquire a lock already held by an older
  *           context, kill ourselves.
  *
  * Since __ww_mutex_add_waiter() orders the wait-list on stamp, we only have to
  * look at waiters before us in the wait-list.
  */
 static inline int
 __ww_mutex_check_kill(struct MUTEX *lock, struct MUTEX_WAITER *waiter,
               struct ww_acquire_ctx *ctx)
 {
     struct ww_mutex *ww = container_of(lock, struct ww_mutex, base);
     struct ww_acquire_ctx *hold_ctx = READ_ONCE(ww->ctx);
     struct MUTEX_WAITER *cur;
 
     if (ctx->acquired == 0)
         return 0;
 
     if (!ctx->is_wait_die) {
         if (ctx->wounded)
             return __ww_mutex_kill(lock, ctx);
 
         return 0;
     }
 
     if (hold_ctx && __ww_ctx_less(ctx, hold_ctx))
         return __ww_mutex_kill(lock, ctx);
 
     /*
      * If there is a waiter in front of us that has a context, then its
      * stamp is earlier than ours and we must kill ourself.
      */
     for (cur = __ww_waiter_prev(lock, waiter); cur;
          cur = __ww_waiter_prev(lock, cur)) {
 
         if (!cur->ww_ctx)
             continue;
 
         return __ww_mutex_kill(lock, ctx);
     }
 
     return 0;
 }
 
 /*
  * Add @waiter to the wait-list, keep the wait-list ordered by stamp, smallest
  * first. Such that older contexts are preferred to acquire the lock over
  * younger contexts.
  *
  * Waiters without context are interspersed in FIFO order.
  *
  * Furthermore, for Wait-Die kill ourself immediately when possible (there are
  * older contexts already waiting) to avoid unnecessary waiting and for
  * Wound-Wait ensure we wound the owning context when it is younger.
  */
 static inline int
 __ww_mutex_add_waiter(struct MUTEX_WAITER *waiter,
               struct MUTEX *lock,
               struct ww_acquire_ctx *ww_ctx)
 {
     struct MUTEX_WAITER *cur, *pos = NULL;
     bool is_wait_die;
 
     if (!ww_ctx) {
         __ww_waiter_add(lock, waiter, NULL);
         return 0;
     }
 
     is_wait_die = ww_ctx->is_wait_die;
 
     /*
      * Add the waiter before the first waiter with a higher stamp.
      * Waiters without a context are skipped to avoid starving
      * them. Wait-Die waiters may die here. Wound-Wait waiters
      * never die here, but they are sorted in stamp order and
      * may wound the lock holder.
      */
     for (cur = __ww_waiter_last(lock); cur;
          cur = __ww_waiter_prev(lock, cur)) {
 
         if (!cur->ww_ctx)
             continue;
 
         if (__ww_ctx_less(ww_ctx, cur->ww_ctx)) {
             /*
              * Wait-Die: if we find an older context waiting, there
              * is no point in queueing behind it, as we'd have to
              * die the moment it would acquire the lock.
              */
             if (is_wait_die) {
                 int ret = __ww_mutex_kill(lock, ww_ctx);
 
                 if (ret)
                     return ret;
             }
 
             break;
         }
 
         pos = cur;
 
         /* Wait-Die: ensure younger waiters die. */
         __ww_mutex_die(lock, cur, ww_ctx);
     }
 
     __ww_waiter_add(lock, waiter, pos);
 
     /*
      * Wound-Wait: if we're blocking on a mutex owned by a younger context,
      * wound that such that we might proceed.
      */
     if (!is_wait_die) {
         struct ww_mutex *ww = container_of(lock, struct ww_mutex, base);
 
         /*
          * See ww_mutex_set_context_fastpath(). Orders setting
          * MUTEX_FLAG_WAITERS vs the ww->ctx load,
          * such that either we or the fastpath will wound @ww->ctx.
          */
         smp_mb();
         __ww_mutex_wound(lock, ww_ctx, ww->ctx);
     }
 
     return 0;
 }
 
 static inline void __ww_mutex_unlock(struct ww_mutex *lock)
 {
     if (lock->ctx) {
 #ifdef DEBUG_WW_MUTEXES
         DEBUG_LOCKS_WARN_ON(!lock->ctx->acquired);
 #endif
         if (lock->ctx->acquired > 0)
             lock->ctx->acquired--;
         lock->ctx = NULL;
     }
 }

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