diff options
| -rw-r--r-- | kern/condition.c | 48 | ||||
| -rw-r--r-- | kern/condition.h | 14 | ||||
| -rw-r--r-- | kern/mutex.h | 9 | ||||
| -rw-r--r-- | kern/sleepq.c | 33 | ||||
| -rw-r--r-- | kern/sleepq.h | 17 | ||||
| -rw-r--r-- | kern/thread.c | 4 | ||||
| -rw-r--r-- | kern/thread.h | 45 | ||||
| -rw-r--r-- | kern/thread_i.h | 12 |
8 files changed, 13 insertions, 169 deletions
diff --git a/kern/condition.c b/kern/condition.c index e6d65951..c407e949 100644 --- a/kern/condition.c +++ b/kern/condition.c @@ -1,5 +1,5 @@ /* - * Copyright (c) 2013-2017 Richard Braun. + * Copyright (c) 2013-2018 Richard Braun. * * This program is free software: you can redistribute it and/or modify * it under the terms of the GNU General Public License as published by @@ -27,46 +27,21 @@ #include <kern/condition_types.h> #include <kern/mutex.h> #include <kern/sleepq.h> -#include <kern/thread.h> static int condition_wait_common(struct condition *condition, struct mutex *mutex, bool timed, uint64_t ticks) { - struct condition *last_cond; struct sleepq *sleepq; unsigned long flags; int error; mutex_assert_locked(mutex); - /* - * Special case : - * - * mutex_lock(lock); - * - * for (;;) { - * while (!done) { - * condition_wait(condition, lock); - * } - * - * do_something(); - * } - * - * Pull the last condition before unlocking the mutex to prevent - * mutex_unlock() from reacquiring the condition sleep queue. - */ - last_cond = thread_pull_last_cond(); - sleepq = sleepq_lend(condition, true, &flags); mutex_unlock(mutex); - if (last_cond != NULL) { - assert(last_cond == condition); - sleepq_wakeup(sleepq); - } - if (timed) { error = sleepq_timedwait(sleepq, "cond", ticks); } else { @@ -74,10 +49,6 @@ condition_wait_common(struct condition *condition, struct mutex *mutex, error = 0; } - if (!error) { - thread_set_last_cond(condition); - } - sleepq_return(sleepq, flags); mutex_lock(mutex); @@ -134,20 +105,3 @@ condition_broadcast(struct condition *condition) sleepq_release(sleepq, flags); } - -void -condition_wakeup(struct condition *condition) -{ - struct sleepq *sleepq; - unsigned long flags; - - sleepq = sleepq_acquire(condition, true, &flags); - - if (sleepq == NULL) { - return; - } - - sleepq_wakeup(sleepq); - - sleepq_release(sleepq, flags); -} diff --git a/kern/condition.h b/kern/condition.h index 90a59f0d..2082bee5 100644 --- a/kern/condition.h +++ b/kern/condition.h @@ -1,5 +1,5 @@ /* - * Copyright (c) 2013-2017 Richard Braun. + * Copyright (c) 2013-2018 Richard Braun. * * This program is free software: you can redistribute it and/or modify * it under the terms of the GNU General Public License as published by @@ -65,16 +65,4 @@ int condition_timedwait(struct condition *condition, void condition_signal(struct condition *condition); void condition_broadcast(struct condition *condition); -/* - * Wake up a pending thread. - * - * This function isn't part of the standard condition variable interface. - * It is used to chain wake-ups to avoid the thundering herd effect. - * When broadcasting a condition variable, a single thread is actually - * awaken. Other threads become "pending waiters", still asleep but - * eligible for wake-up when the mutex associated to the condition variable, - * relocked when returning from condition_wait(), is finally unlocked. - */ -void condition_wakeup(struct condition *condition); - #endif /* _KERN_CONDITION_H */ diff --git a/kern/mutex.h b/kern/mutex.h index 10872e6e..b4332dea 100644 --- a/kern/mutex.h +++ b/kern/mutex.h @@ -1,5 +1,5 @@ /* - * Copyright (c) 2013-2017 Richard Braun. + * Copyright (c) 2013-2018 Richard Braun. * * This program is free software: you can redistribute it and/or modify * it under the terms of the GNU General Public License as published by @@ -37,7 +37,6 @@ #include <kern/init.h> #include <kern/mutex_types.h> -#include <kern/thread.h> /* * Initialize a mutex. @@ -102,12 +101,6 @@ static inline void mutex_unlock(struct mutex *mutex) { mutex_impl_unlock(mutex); - - /* - * If this mutex was used along with a condition variable, wake up - * a potential pending waiter. - */ - thread_wakeup_last_cond(); } /* diff --git a/kern/sleepq.c b/kern/sleepq.c index 0d04c6ea..1fd1ac42 100644 --- a/kern/sleepq.c +++ b/kern/sleepq.c @@ -1,5 +1,5 @@ /* - * Copyright (c) 2017 Richard Braun. + * Copyright (c) 2017-2018 Richard Braun. * * This program is free software: you can redistribute it and/or modify * it under the terms of the GNU General Public License as published by @@ -503,46 +503,23 @@ sleepq_signal(struct sleepq *sleepq) sleepq_waiter_wakeup(waiter); } -static void -sleepq_wakeup_common(struct sleepq *sleepq) -{ - struct sleepq_waiter *waiter; - - assert(!list_empty(&sleepq->waiters)); - - waiter = list_last_entry(&sleepq->waiters, struct sleepq_waiter, node); - sleepq_waiter_wakeup(waiter); -} - void sleepq_broadcast(struct sleepq *sleepq) { struct sleepq_waiter *waiter; if (sleepq->oldest_waiter == NULL) { - goto out; + return; } + sleepq->oldest_waiter = NULL; + list_for_each_entry(&sleepq->waiters, waiter, node) { sleepq_waiter_set_pending_wakeup(waiter); + sleepq_waiter_wakeup(waiter); if (waiter == sleepq->oldest_waiter) { break; } } - - sleepq->oldest_waiter = NULL; - -out: - sleepq_wakeup_common(sleepq); -} - -void -sleepq_wakeup(struct sleepq *sleepq) -{ - if (list_empty(&sleepq->waiters)) { - return; - } - - sleepq_wakeup_common(sleepq); } diff --git a/kern/sleepq.h b/kern/sleepq.h index 007e3f2f..213925cb 100644 --- a/kern/sleepq.h +++ b/kern/sleepq.h @@ -1,5 +1,5 @@ /* - * Copyright (c) 2017 Richard Braun. + * Copyright (c) 2017-2018 Richard Braun. * * This program is free software: you can redistribute it and/or modify * it under the terms of the GNU General Public License as published by @@ -125,25 +125,12 @@ int sleepq_timedwait(struct sleepq *sleepq, const char *wchan, uint64_t ticks); * At least one thread is awaken if any threads are waiting on the sleep * queue. * - * A broadcast differs only by also making all currently waiting threads - * pending for wake-up. As with sleepq_signal, a single thread may be - * awaken. The rationale is to force users to implement "chained waking" - * in order to avoid the thundering herd effect. + * Broadcasting a sleep queue wakes up all waiting threads. */ void sleepq_signal(struct sleepq *sleepq); void sleepq_broadcast(struct sleepq *sleepq); /* - * Wake up a pending thread. - * - * This function may only wake up a thread pending for wake-up after a - * broadcast. It is used to chain wake-ups to avoid the thundering herd - * effect. If there are no threads pending for wake-up, this function - * does nothing. - */ -void sleepq_wakeup(struct sleepq *sleepq); - -/* * This init operation provides : * - sleepq creation * - module fully initialized diff --git a/kern/thread.c b/kern/thread.c index 330b5375..f41e5936 100644 --- a/kern/thread.c +++ b/kern/thread.c @@ -1,5 +1,5 @@ /* - * Copyright (c) 2012-2017 Richard Braun. + * Copyright (c) 2012-2018 Richard Braun. * * This program is free software: you can redistribute it and/or modify * it under the terms of the GNU General Public License as published by @@ -92,7 +92,6 @@ #include <kern/atomic.h> #include <kern/clock.h> -#include <kern/condition.h> #include <kern/cpumap.h> #include <kern/error.h> #include <kern/init.h> @@ -1821,7 +1820,6 @@ thread_init(struct thread *thread, void *stack, } turnstile_td_init(&thread->turnstile_td); - thread->last_cond = NULL; thread->propagate_priority = false; thread->preempt_level = THREAD_SUSPEND_PREEMPT_LEVEL; thread->pin_level = 0; diff --git a/kern/thread.h b/kern/thread.h index 4761e1ec..8084c114 100644 --- a/kern/thread.h +++ b/kern/thread.h @@ -1,5 +1,5 @@ /* - * Copyright (c) 2012-2017 Richard Braun. + * Copyright (c) 2012-2018 Richard Braun. * * This program is free software: you can redistribute it and/or modify * it under the terms of the GNU General Public License as published by @@ -41,7 +41,6 @@ #include <kern/atomic.h> #include <kern/init.h> -#include <kern/condition.h> #include <kern/cpumap.h> #include <kern/kernel.h> #include <kern/macros.h> @@ -442,48 +441,6 @@ thread_sleepq_return(struct sleepq *sleepq) } /* - * Condition variable related functions. - */ - -static inline void -thread_set_last_cond(struct condition *last_cond) -{ - struct thread *thread; - - thread = thread_self(); - assert(thread->last_cond == NULL); - thread->last_cond = last_cond; -} - -static inline struct condition * -thread_pull_last_cond(void) -{ - struct condition *last_cond; - struct thread *thread; - - thread = thread_self(); - last_cond = thread->last_cond; - - if (last_cond != NULL) { - thread->last_cond = NULL; - } - - return last_cond; -} - -static inline void -thread_wakeup_last_cond(void) -{ - struct condition *last_cond; - - last_cond = thread_pull_last_cond(); - - if (last_cond != NULL) { - condition_wakeup(last_cond); - } -} - -/* * Turnstile lending functions. */ diff --git a/kern/thread_i.h b/kern/thread_i.h index 067b31ed..96ce100a 100644 --- a/kern/thread_i.h +++ b/kern/thread_i.h @@ -1,5 +1,5 @@ /* - * Copyright (c) 2017 Richard Braun. + * Copyright (c) 2017-2018 Richard Braun. * * This program is free software: you can redistribute it and/or modify * it under the terms of the GNU General Public License as published by @@ -22,7 +22,6 @@ #include <stdbool.h> #include <kern/atomic.h> -#include <kern/condition_types.h> #include <kern/cpumap.h> #include <kern/list_types.h> #include <kern/spinlock_types.h> @@ -121,15 +120,6 @@ struct thread { /* Turnstile available for lending */ struct turnstile *priv_turnstile; /* (-) */ - /* - * When a thread wakes up after waiting for a condition variable, - * it sets this variable so that other waiters are only awaken - * after the associated mutex has actually been released. - * - * This member is thread-local. - */ - struct condition *last_cond; /* (-) */ - struct turnstile_td turnstile_td; /* (t) */ /* True if priority must be propagated when preemption is reenabled */ |