/* 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, unsigned long *flags){ raw_spin_lock_irqsave(&lock->wait_lock, *flags);} static inline void unlock_wait_lock(struct mutex *lock, unsigned long *flags){ raw_spin_unlock_irqrestore(&lock->wait_lock, *flags);} 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, unsigned long *flags){ raw_spin_lock_irqsave(&lock->rtmutex.wait_lock, *flags);} static inline void unlock_wait_lock(struct rt_mutex *lock, unsigned long *flags){ raw_spin_unlock_irqrestore(&lock->rtmutex.wait_lock, *flags);} 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 voidww_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_or_dl_prio(a_prio) || rt_or_dl_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, struct wake_q_head *wake_q){ 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_q_add(wake_q, 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 wake_q_head *wake_q){ 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_q_add(wake_q, 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 wake_q_head *wake_q){ 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, wake_q) || __ww_mutex_wound(lock, cur->ww_ctx, ww_ctx, wake_q)) 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 voidww_mutex_set_context_fastpath(struct ww_mutex *lock, struct ww_acquire_ctx *ctx){ DEFINE_WAKE_Q(wake_q); unsigned long flags; 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, &flags); __ww_mutex_check_waiters(&lock->base, ctx, &wake_q); preempt_disable(); unlock_wait_lock(&lock->base, &flags); wake_up_q(&wake_q); preempt_enable();} 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 wake_q_head *wake_q)Lines 1–500 of 578. Load more
/* 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, unsigned long *flags) { raw_spin_lock_irqsave(&lock->wait_lock, *flags); } static inline void unlock_wait_lock(struct mutex *lock, unsigned long *flags) { raw_spin_unlock_irqrestore(&lock->wait_lock, *flags); } 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, unsigned long *flags) { raw_spin_lock_irqsave(&lock->rtmutex.wait_lock, *flags); } static inline void unlock_wait_lock(struct rt_mutex *lock, unsigned long *flags) { raw_spin_unlock_irqrestore(&lock->rtmutex.wait_lock, *flags); } 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_or_dl_prio(a_prio) || rt_or_dl_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, struct wake_q_head *wake_q) { 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_q_add(wake_q, 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 wake_q_head *wake_q) { 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_q_add(wake_q, 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 wake_q_head *wake_q) { 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, wake_q) || __ww_mutex_wound(lock, cur->ww_ctx, ww_ctx, wake_q)) 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) { DEFINE_WAKE_Q(wake_q); unsigned long flags; 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, &flags); __ww_mutex_check_waiters(&lock->base, ctx, &wake_q); preempt_disable(); unlock_wait_lock(&lock->base, &flags); wake_up_q(&wake_q); preempt_enable(); } 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 wake_q_head *wake_q)