| /trunk/kernel/generic/src/synch/rwlock.c |
|---|
| 0,0 → 1,389 |
| /* |
| * Copyright (C) 2001-2004 Jakub Jermar |
| * All rights reserved. |
| * |
| * Redistribution and use in source and binary forms, with or without |
| * modification, are permitted provided that the following conditions |
| * are met: |
| * |
| * - Redistributions of source code must retain the above copyright |
| * notice, this list of conditions and the following disclaimer. |
| * - Redistributions in binary form must reproduce the above copyright |
| * notice, this list of conditions and the following disclaimer in the |
| * documentation and/or other materials provided with the distribution. |
| * - The name of the author may not be used to endorse or promote products |
| * derived from this software without specific prior written permission. |
| * |
| * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR |
| * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES |
| * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. |
| * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, |
| * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT |
| * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, |
| * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY |
| * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT |
| * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF |
| * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
| */ |
| /** @addtogroup sync |
| * @{ |
| */ |
| /** |
| * @file |
| * @brief Reader/Writer locks. |
| * |
| * A reader/writer lock can be held by multiple readers at a time. |
| * Or it can be exclusively held by a sole writer at a time. |
| * |
| * These locks are not recursive. |
| * Because a technique called direct hand-off is used and because |
| * waiting takes place in a single wait queue, neither readers |
| * nor writers will suffer starvation. |
| * |
| * If there is a writer followed by a reader waiting for the rwlock |
| * and the writer times out, all leading readers are automatically woken up |
| * and allowed in. |
| */ |
| /* |
| * NOTE ON rwlock_holder_type |
| * This field is set on an attempt to acquire the exclusive mutex |
| * to the respective value depending whether the caller is a reader |
| * or a writer. The field is examined only if the thread had been |
| * previously blocked on the exclusive mutex. Thus it is save |
| * to store the rwlock type in the thread structure, because |
| * each thread can block on only one rwlock at a time. |
| */ |
| #include <synch/rwlock.h> |
| #include <synch/spinlock.h> |
| #include <synch/mutex.h> |
| #include <synch/waitq.h> |
| #include <synch/synch.h> |
| #include <adt/list.h> |
| #include <typedefs.h> |
| #include <arch/asm.h> |
| #include <arch.h> |
| #include <proc/thread.h> |
| #include <panic.h> |
| #define ALLOW_ALL 0 |
| #define ALLOW_READERS_ONLY 1 |
| static void let_others_in(rwlock_t *rwl, int readers_only); |
| static void release_spinlock(void *arg); |
| /** Initialize reader/writer lock |
| * |
| * Initialize reader/writer lock. |
| * |
| * @param rwl Reader/Writer lock. |
| */ |
| void rwlock_initialize(rwlock_t *rwl) { |
| spinlock_initialize(&rwl->lock, "rwlock_t"); |
| mutex_initialize(&rwl->exclusive); |
| rwl->readers_in = 0; |
| } |
| /** Acquire reader/writer lock for reading |
| * |
| * Acquire reader/writer lock for reading. |
| * Timeout and willingness to block may be specified. |
| * |
| * @param rwl Reader/Writer lock. |
| * @param usec Timeout in microseconds. |
| * @param flags Specify mode of operation. |
| * |
| * For exact description of possible combinations of |
| * usec and flags, see comment for waitq_sleep_timeout(). |
| * |
| * @return See comment for waitq_sleep_timeout(). |
| */ |
| int _rwlock_write_lock_timeout(rwlock_t *rwl, uint32_t usec, int flags) |
| { |
| ipl_t ipl; |
| int rc; |
| ipl = interrupts_disable(); |
| spinlock_lock(&THREAD->lock); |
| THREAD->rwlock_holder_type = RWLOCK_WRITER; |
| spinlock_unlock(&THREAD->lock); |
| interrupts_restore(ipl); |
| /* |
| * Writers take the easy part. |
| * They just need to acquire the exclusive mutex. |
| */ |
| rc = _mutex_lock_timeout(&rwl->exclusive, usec, flags); |
| if (SYNCH_FAILED(rc)) { |
| /* |
| * Lock operation timed out or was interrupted. |
| * The state of rwl is UNKNOWN at this point. |
| * No claims about its holder can be made. |
| */ |
| ipl = interrupts_disable(); |
| spinlock_lock(&rwl->lock); |
| /* |
| * Now when rwl is locked, we can inspect it again. |
| * If it is held by some readers already, we can let |
| * readers from the head of the wait queue in. |
| */ |
| if (rwl->readers_in) |
| let_others_in(rwl, ALLOW_READERS_ONLY); |
| spinlock_unlock(&rwl->lock); |
| interrupts_restore(ipl); |
| } |
| return rc; |
| } |
| /** Acquire reader/writer lock for writing |
| * |
| * Acquire reader/writer lock for writing. |
| * Timeout and willingness to block may be specified. |
| * |
| * @param rwl Reader/Writer lock. |
| * @param usec Timeout in microseconds. |
| * @param flags Select mode of operation. |
| * |
| * For exact description of possible combinations of |
| * usec and flags, see comment for waitq_sleep_timeout(). |
| * |
| * @return See comment for waitq_sleep_timeout(). |
| */ |
| int _rwlock_read_lock_timeout(rwlock_t *rwl, uint32_t usec, int flags) |
| { |
| int rc; |
| ipl_t ipl; |
| ipl = interrupts_disable(); |
| spinlock_lock(&THREAD->lock); |
| THREAD->rwlock_holder_type = RWLOCK_READER; |
| spinlock_unlock(&THREAD->lock); |
| spinlock_lock(&rwl->lock); |
| /* |
| * Find out whether we can get what we want without blocking. |
| */ |
| rc = mutex_trylock(&rwl->exclusive); |
| if (SYNCH_FAILED(rc)) { |
| /* |
| * 'exclusive' mutex is being held by someone else. |
| * If the holder is a reader and there is no one |
| * else waiting for it, we can enter the critical |
| * section. |
| */ |
| if (rwl->readers_in) { |
| spinlock_lock(&rwl->exclusive.sem.wq.lock); |
| if (list_empty(&rwl->exclusive.sem.wq.head)) { |
| /* |
| * We can enter. |
| */ |
| spinlock_unlock(&rwl->exclusive.sem.wq.lock); |
| goto shortcut; |
| } |
| spinlock_unlock(&rwl->exclusive.sem.wq.lock); |
| } |
| /* |
| * In order to prevent a race condition when a reader |
| * could block another reader at the head of the waitq, |
| * we register a function to unlock rwl->lock |
| * after this thread is put asleep. |
| */ |
| #ifdef CONFIG_SMP |
| thread_register_call_me(release_spinlock, &rwl->lock); |
| #else |
| thread_register_call_me(release_spinlock, NULL); |
| #endif |
| rc = _mutex_lock_timeout(&rwl->exclusive, usec, flags); |
| switch (rc) { |
| case ESYNCH_WOULD_BLOCK: |
| /* |
| * release_spinlock() wasn't called |
| */ |
| thread_register_call_me(NULL, NULL); |
| spinlock_unlock(&rwl->lock); |
| case ESYNCH_TIMEOUT: |
| case ESYNCH_INTERRUPTED: |
| /* |
| * The sleep timed out. |
| * We just restore interrupt priority level. |
| */ |
| case ESYNCH_OK_BLOCKED: |
| /* |
| * We were woken with rwl->readers_in already incremented. |
| * Note that this arrangement avoids race condition between |
| * two concurrent readers. (Race is avoided if 'exclusive' is |
| * locked at the same time as 'readers_in' is incremented. |
| * Same time means both events happen atomically when |
| * rwl->lock is held.) |
| */ |
| interrupts_restore(ipl); |
| break; |
| case ESYNCH_OK_ATOMIC: |
| panic("_mutex_lock_timeout()==ESYNCH_OK_ATOMIC\n"); |
| break; |
| default: |
| panic("invalid ESYNCH\n"); |
| break; |
| } |
| return rc; |
| } |
| shortcut: |
| /* |
| * We can increment readers_in only if we didn't go to sleep. |
| * For sleepers, rwlock_let_others_in() will do the job. |
| */ |
| rwl->readers_in++; |
| spinlock_unlock(&rwl->lock); |
| interrupts_restore(ipl); |
| return ESYNCH_OK_ATOMIC; |
| } |
| /** Release reader/writer lock held by writer |
| * |
| * Release reader/writer lock held by writer. |
| * Handoff reader/writer lock ownership directly |
| * to waiting readers or a writer. |
| * |
| * @param rwl Reader/Writer lock. |
| */ |
| void rwlock_write_unlock(rwlock_t *rwl) |
| { |
| ipl_t ipl; |
| ipl = interrupts_disable(); |
| spinlock_lock(&rwl->lock); |
| let_others_in(rwl, ALLOW_ALL); |
| spinlock_unlock(&rwl->lock); |
| interrupts_restore(ipl); |
| } |
| /** Release reader/writer lock held by reader |
| * |
| * Release reader/writer lock held by reader. |
| * Handoff reader/writer lock ownership directly |
| * to a waiting writer or don't do anything if more |
| * readers poses the lock. |
| * |
| * @param rwl Reader/Writer lock. |
| */ |
| void rwlock_read_unlock(rwlock_t *rwl) |
| { |
| ipl_t ipl; |
| ipl = interrupts_disable(); |
| spinlock_lock(&rwl->lock); |
| if (!--rwl->readers_in) |
| let_others_in(rwl, ALLOW_ALL); |
| spinlock_unlock(&rwl->lock); |
| interrupts_restore(ipl); |
| } |
| /** Direct handoff of reader/writer lock ownership. |
| * |
| * Direct handoff of reader/writer lock ownership |
| * to waiting readers or a writer. |
| * |
| * Must be called with rwl->lock locked. |
| * Must be called with interrupts_disable()'d. |
| * |
| * @param rwl Reader/Writer lock. |
| * @param readers_only See the description below. |
| * |
| * If readers_only is false: (unlock scenario) |
| * Let the first sleeper on 'exclusive' mutex in, no matter |
| * whether it is a reader or a writer. If there are more leading |
| * readers in line, let each of them in. |
| * |
| * Otherwise: (timeout scenario) |
| * Let all leading readers in. |
| */ |
| void let_others_in(rwlock_t *rwl, int readers_only) |
| { |
| rwlock_type_t type = RWLOCK_NONE; |
| thread_t *t = NULL; |
| bool one_more = true; |
| spinlock_lock(&rwl->exclusive.sem.wq.lock); |
| if (!list_empty(&rwl->exclusive.sem.wq.head)) |
| t = list_get_instance(rwl->exclusive.sem.wq.head.next, thread_t, wq_link); |
| do { |
| if (t) { |
| spinlock_lock(&t->lock); |
| type = t->rwlock_holder_type; |
| spinlock_unlock(&t->lock); |
| } |
| /* |
| * If readers_only is true, we wake all leading readers |
| * if and only if rwl is locked by another reader. |
| * Assumption: readers_only ==> rwl->readers_in |
| */ |
| if (readers_only && (type != RWLOCK_READER)) |
| break; |
| if (type == RWLOCK_READER) { |
| /* |
| * Waking up a reader. |
| * We are responsible for incrementing rwl->readers_in for it. |
| */ |
| rwl->readers_in++; |
| } |
| /* |
| * Only the last iteration through this loop can increment |
| * rwl->exclusive.sem.wq.missed_wakeup's. All preceeding |
| * iterations will wake up a thread. |
| */ |
| /* We call the internal version of waitq_wakeup, which |
| * relies on the fact that the waitq is already locked. |
| */ |
| _waitq_wakeup_unsafe(&rwl->exclusive.sem.wq, WAKEUP_FIRST); |
| t = NULL; |
| if (!list_empty(&rwl->exclusive.sem.wq.head)) { |
| t = list_get_instance(rwl->exclusive.sem.wq.head.next, thread_t, wq_link); |
| if (t) { |
| spinlock_lock(&t->lock); |
| if (t->rwlock_holder_type != RWLOCK_READER) |
| one_more = false; |
| spinlock_unlock(&t->lock); |
| } |
| } |
| } while ((type == RWLOCK_READER) && t && one_more); |
| spinlock_unlock(&rwl->exclusive.sem.wq.lock); |
| } |
| /** Release spinlock callback |
| * |
| * This is a callback function invoked from the scheduler. |
| * The callback is registered in _rwlock_read_lock_timeout(). |
| * |
| * @param arg Spinlock. |
| */ |
| void release_spinlock(void *arg) |
| { |
| spinlock_unlock((spinlock_t *) arg); |
| } |
| /** @} |
| */ |
| /trunk/kernel/generic/src/synch/mutex.c |
|---|
| 0,0 → 1,84 |
| /* |
| * Copyright (C) 2001-2004 Jakub Jermar |
| * All rights reserved. |
| * |
| * Redistribution and use in source and binary forms, with or without |
| * modification, are permitted provided that the following conditions |
| * are met: |
| * |
| * - Redistributions of source code must retain the above copyright |
| * notice, this list of conditions and the following disclaimer. |
| * - Redistributions in binary form must reproduce the above copyright |
| * notice, this list of conditions and the following disclaimer in the |
| * documentation and/or other materials provided with the distribution. |
| * - The name of the author may not be used to endorse or promote products |
| * derived from this software without specific prior written permission. |
| * |
| * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR |
| * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES |
| * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. |
| * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, |
| * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT |
| * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, |
| * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY |
| * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT |
| * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF |
| * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
| */ |
| /** @addtogroup sync |
| * @{ |
| */ |
| /** |
| * @file |
| * @brief Mutexes. |
| */ |
| #include <synch/mutex.h> |
| #include <synch/semaphore.h> |
| #include <synch/synch.h> |
| /** Initialize mutex |
| * |
| * Initialize mutex. |
| * |
| * @param mtx Mutex. |
| */ |
| void mutex_initialize(mutex_t *mtx) |
| { |
| semaphore_initialize(&mtx->sem, 1); |
| } |
| /** Acquire mutex |
| * |
| * Acquire mutex. |
| * Timeout mode and non-blocking mode can be requested. |
| * |
| * @param mtx Mutex. |
| * @param usec Timeout in microseconds. |
| * @param flags Specify mode of operation. |
| * |
| * For exact description of possible combinations of |
| * usec and flags, see comment for waitq_sleep_timeout(). |
| * |
| * @return See comment for waitq_sleep_timeout(). |
| */ |
| int _mutex_lock_timeout(mutex_t *mtx, uint32_t usec, int flags) |
| { |
| return _semaphore_down_timeout(&mtx->sem, usec, flags); |
| } |
| /** Release mutex |
| * |
| * Release mutex. |
| * |
| * @param mtx Mutex. |
| */ |
| void mutex_unlock(mutex_t *mtx) |
| { |
| semaphore_up(&mtx->sem); |
| } |
| /** @} |
| */ |
| /trunk/kernel/generic/src/synch/spinlock.c |
|---|
| 0,0 → 1,162 |
| /* |
| * Copyright (C) 2001-2004 Jakub Jermar |
| * All rights reserved. |
| * |
| * Redistribution and use in source and binary forms, with or without |
| * modification, are permitted provided that the following conditions |
| * are met: |
| * |
| * - Redistributions of source code must retain the above copyright |
| * notice, this list of conditions and the following disclaimer. |
| * - Redistributions in binary form must reproduce the above copyright |
| * notice, this list of conditions and the following disclaimer in the |
| * documentation and/or other materials provided with the distribution. |
| * - The name of the author may not be used to endorse or promote products |
| * derived from this software without specific prior written permission. |
| * |
| * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR |
| * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES |
| * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. |
| * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, |
| * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT |
| * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, |
| * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY |
| * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT |
| * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF |
| * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
| */ |
| /** @addtogroup sync |
| * @{ |
| */ |
| /** |
| * @file |
| * @brief Spinlocks. |
| */ |
| #include <synch/spinlock.h> |
| #include <atomic.h> |
| #include <arch/barrier.h> |
| #include <arch.h> |
| #include <preemption.h> |
| #include <print.h> |
| #include <debug.h> |
| #include <symtab.h> |
| #ifdef CONFIG_FB |
| #include <genarch/fb/fb.h> |
| #endif |
| #ifdef CONFIG_SMP |
| /** Initialize spinlock |
| * |
| * Initialize spinlock. |
| * |
| * @param sl Pointer to spinlock_t structure. |
| */ |
| void spinlock_initialize(spinlock_t *sl, char *name) |
| { |
| atomic_set(&sl->val, 0); |
| #ifdef CONFIG_DEBUG_SPINLOCK |
| sl->name = name; |
| #endif |
| } |
| /** Lock spinlock |
| * |
| * Lock spinlock. |
| * This version has limitted ability to report |
| * possible occurence of deadlock. |
| * |
| * @param sl Pointer to spinlock_t structure. |
| */ |
| #ifdef CONFIG_DEBUG_SPINLOCK |
| #define DEADLOCK_THRESHOLD 100000000 |
| void spinlock_lock_debug(spinlock_t *sl) |
| { |
| count_t i = 0; |
| char *symbol; |
| bool deadlock_reported = false; |
| preemption_disable(); |
| while (test_and_set(&sl->val)) { |
| /* |
| * We need to be careful about printflock and fb_lock. |
| * Both of them are used to report deadlocks via |
| * printf() and fb_putchar(). |
| * |
| * We trust our code that there is no possible deadlock |
| * caused by these two locks (except when an exception |
| * is triggered for instance by printf() or fb_putchar()). |
| * However, we encountered false positives caused by very |
| * slow VESA framebuffer interaction (especially when |
| * run in a simulator) that caused problems with both |
| * printflock and fb_lock. |
| * |
| * Possible deadlocks on both printflock and fb_lock |
| * are therefore not reported as they would cause an |
| * infinite recursion. |
| */ |
| if (sl == &printflock) |
| continue; |
| #ifdef CONFIG_FB |
| if (sl == &fb_lock) |
| continue; |
| #endif |
| if (i++ > DEADLOCK_THRESHOLD) { |
| printf("cpu%d: looping on spinlock %.*p:%s, caller=%.*p", |
| CPU->id, sizeof(uintptr_t) * 2, sl, sl->name, sizeof(uintptr_t) * 2, CALLER); |
| symbol = get_symtab_entry(CALLER); |
| if (symbol) |
| printf("(%s)", symbol); |
| printf("\n"); |
| i = 0; |
| deadlock_reported = true; |
| } |
| } |
| if (deadlock_reported) |
| printf("cpu%d: not deadlocked\n", CPU->id); |
| /* |
| * Prevent critical section code from bleeding out this way up. |
| */ |
| CS_ENTER_BARRIER(); |
| } |
| #endif |
| /** Lock spinlock conditionally |
| * |
| * Lock spinlock conditionally. |
| * If the spinlock is not available at the moment, |
| * signal failure. |
| * |
| * @param sl Pointer to spinlock_t structure. |
| * |
| * @return Zero on failure, non-zero otherwise. |
| */ |
| int spinlock_trylock(spinlock_t *sl) |
| { |
| int rc; |
| preemption_disable(); |
| rc = !test_and_set(&sl->val); |
| /* |
| * Prevent critical section code from bleeding out this way up. |
| */ |
| CS_ENTER_BARRIER(); |
| if (!rc) |
| preemption_enable(); |
| return rc; |
| } |
| #endif |
| /** @} |
| */ |
| /trunk/kernel/generic/src/synch/semaphore.c |
|---|
| 0,0 → 1,98 |
| /* |
| * Copyright (C) 2001-2004 Jakub Jermar |
| * All rights reserved. |
| * |
| * Redistribution and use in source and binary forms, with or without |
| * modification, are permitted provided that the following conditions |
| * are met: |
| * |
| * - Redistributions of source code must retain the above copyright |
| * notice, this list of conditions and the following disclaimer. |
| * - Redistributions in binary form must reproduce the above copyright |
| * notice, this list of conditions and the following disclaimer in the |
| * documentation and/or other materials provided with the distribution. |
| * - The name of the author may not be used to endorse or promote products |
| * derived from this software without specific prior written permission. |
| * |
| * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR |
| * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES |
| * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. |
| * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, |
| * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT |
| * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, |
| * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY |
| * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT |
| * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF |
| * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
| */ |
| /** @addtogroup sync |
| * @{ |
| */ |
| /** |
| * @file |
| * @brief Semaphores. |
| */ |
| #include <synch/semaphore.h> |
| #include <synch/waitq.h> |
| #include <synch/spinlock.h> |
| #include <synch/synch.h> |
| #include <arch/asm.h> |
| #include <arch.h> |
| /** Initialize semaphore |
| * |
| * Initialize semaphore. |
| * |
| * @param s Semaphore. |
| * @param val Maximal number of threads allowed to enter critical section. |
| */ |
| void semaphore_initialize(semaphore_t *s, int val) |
| { |
| ipl_t ipl; |
| waitq_initialize(&s->wq); |
| ipl = interrupts_disable(); |
| spinlock_lock(&s->wq.lock); |
| s->wq.missed_wakeups = val; |
| spinlock_unlock(&s->wq.lock); |
| interrupts_restore(ipl); |
| } |
| /** Semaphore down |
| * |
| * Semaphore down. |
| * Conditional mode and mode with timeout can be requested. |
| * |
| * @param s Semaphore. |
| * @param usec Timeout in microseconds. |
| * @param flags Select mode of operation. |
| * |
| * For exact description of possible combinations of |
| * usec and flags, see comment for waitq_sleep_timeout(). |
| * |
| * @return See comment for waitq_sleep_timeout(). |
| */ |
| int _semaphore_down_timeout(semaphore_t *s, uint32_t usec, int flags) |
| { |
| return waitq_sleep_timeout(&s->wq, usec, flags); |
| } |
| /** Semaphore up |
| * |
| * Semaphore up. |
| * |
| * @param s Semaphore. |
| */ |
| void semaphore_up(semaphore_t *s) |
| { |
| waitq_wakeup(&s->wq, WAKEUP_FIRST); |
| } |
| /** @} |
| */ |
| /trunk/kernel/generic/src/synch/waitq.c |
|---|
| 0,0 → 1,454 |
| /* |
| * Copyright (C) 2001-2004 Jakub Jermar |
| * All rights reserved. |
| * |
| * Redistribution and use in source and binary forms, with or without |
| * modification, are permitted provided that the following conditions |
| * are met: |
| * |
| * - Redistributions of source code must retain the above copyright |
| * notice, this list of conditions and the following disclaimer. |
| * - Redistributions in binary form must reproduce the above copyright |
| * notice, this list of conditions and the following disclaimer in the |
| * documentation and/or other materials provided with the distribution. |
| * - The name of the author may not be used to endorse or promote products |
| * derived from this software without specific prior written permission. |
| * |
| * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR |
| * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES |
| * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. |
| * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, |
| * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT |
| * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, |
| * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY |
| * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT |
| * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF |
| * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
| */ |
| /** @addtogroup sync |
| * @{ |
| */ |
| /** |
| * @file |
| * @brief Wait queue. |
| * |
| * Wait queue is the basic synchronization primitive upon which all |
| * other synchronization primitives build. |
| * |
| * It allows threads to wait for an event in first-come, first-served |
| * fashion. Conditional operation as well as timeouts and interruptions |
| * are supported. |
| */ |
| #include <synch/waitq.h> |
| #include <synch/synch.h> |
| #include <synch/spinlock.h> |
| #include <proc/thread.h> |
| #include <proc/scheduler.h> |
| #include <arch/asm.h> |
| #include <arch/types.h> |
| #include <typedefs.h> |
| #include <time/timeout.h> |
| #include <arch.h> |
| #include <context.h> |
| #include <adt/list.h> |
| static void waitq_timeouted_sleep(void *data); |
| /** Initialize wait queue |
| * |
| * Initialize wait queue. |
| * |
| * @param wq Pointer to wait queue to be initialized. |
| */ |
| void waitq_initialize(waitq_t *wq) |
| { |
| spinlock_initialize(&wq->lock, "waitq_lock"); |
| list_initialize(&wq->head); |
| wq->missed_wakeups = 0; |
| } |
| /** Handle timeout during waitq_sleep_timeout() call |
| * |
| * This routine is called when waitq_sleep_timeout() timeouts. |
| * Interrupts are disabled. |
| * |
| * It is supposed to try to remove 'its' thread from the wait queue; |
| * it can eventually fail to achieve this goal when these two events |
| * overlap. In that case it behaves just as though there was no |
| * timeout at all. |
| * |
| * @param data Pointer to the thread that called waitq_sleep_timeout(). |
| */ |
| void waitq_timeouted_sleep(void *data) |
| { |
| thread_t *t = (thread_t *) data; |
| waitq_t *wq; |
| bool do_wakeup = false; |
| spinlock_lock(&threads_lock); |
| if (!thread_exists(t)) |
| goto out; |
| grab_locks: |
| spinlock_lock(&t->lock); |
| if ((wq = t->sleep_queue)) { /* assignment */ |
| if (!spinlock_trylock(&wq->lock)) { |
| spinlock_unlock(&t->lock); |
| goto grab_locks; /* avoid deadlock */ |
| } |
| list_remove(&t->wq_link); |
| t->saved_context = t->sleep_timeout_context; |
| do_wakeup = true; |
| t->sleep_queue = NULL; |
| spinlock_unlock(&wq->lock); |
| } |
| t->timeout_pending = false; |
| spinlock_unlock(&t->lock); |
| if (do_wakeup) |
| thread_ready(t); |
| out: |
| spinlock_unlock(&threads_lock); |
| } |
| /** Interrupt sleeping thread. |
| * |
| * This routine attempts to interrupt a thread from its sleep in a waitqueue. |
| * If the thread is not found sleeping, no action is taken. |
| * |
| * @param t Thread to be interrupted. |
| */ |
| void waitq_interrupt_sleep(thread_t *t) |
| { |
| waitq_t *wq; |
| bool do_wakeup = false; |
| ipl_t ipl; |
| ipl = interrupts_disable(); |
| spinlock_lock(&threads_lock); |
| if (!thread_exists(t)) |
| goto out; |
| grab_locks: |
| spinlock_lock(&t->lock); |
| if ((wq = t->sleep_queue)) { /* assignment */ |
| if (!(t->sleep_interruptible)) { |
| /* |
| * The sleep cannot be interrupted. |
| */ |
| spinlock_unlock(&t->lock); |
| goto out; |
| } |
| if (!spinlock_trylock(&wq->lock)) { |
| spinlock_unlock(&t->lock); |
| goto grab_locks; /* avoid deadlock */ |
| } |
| if (t->timeout_pending && timeout_unregister(&t->sleep_timeout)) |
| t->timeout_pending = false; |
| list_remove(&t->wq_link); |
| t->saved_context = t->sleep_interruption_context; |
| do_wakeup = true; |
| t->sleep_queue = NULL; |
| spinlock_unlock(&wq->lock); |
| } |
| spinlock_unlock(&t->lock); |
| if (do_wakeup) |
| thread_ready(t); |
| out: |
| spinlock_unlock(&threads_lock); |
| interrupts_restore(ipl); |
| } |
| /** Sleep until either wakeup, timeout or interruption occurs |
| * |
| * This is a sleep implementation which allows itself to time out or to be |
| * interrupted from the sleep, restoring a failover context. |
| * |
| * Sleepers are organised in a FIFO fashion in a structure called wait queue. |
| * |
| * This function is really basic in that other functions as waitq_sleep() |
| * and all the *_timeout() functions use it. |
| * |
| * @param wq Pointer to wait queue. |
| * @param usec Timeout in microseconds. |
| * @param flags Specify mode of the sleep. |
| * |
| * The sleep can be interrupted only if the |
| * SYNCH_FLAGS_INTERRUPTIBLE bit is specified in flags. |
| * If usec is greater than zero, regardless of the value of the |
| * SYNCH_FLAGS_NON_BLOCKING bit in flags, the call will not return until either timeout, |
| * interruption or wakeup comes. |
| * |
| * If usec is zero and the SYNCH_FLAGS_NON_BLOCKING bit is not set in flags, the call |
| * will not return until wakeup or interruption comes. |
| * |
| * If usec is zero and the SYNCH_FLAGS_NON_BLOCKING bit is set in flags, the call will |
| * immediately return, reporting either success or failure. |
| * |
| * @return Returns one of: ESYNCH_WOULD_BLOCK, ESYNCH_TIMEOUT, ESYNCH_INTERRUPTED, |
| * ESYNCH_OK_ATOMIC, ESYNCH_OK_BLOCKED. |
| * |
| * @li ESYNCH_WOULD_BLOCK means that the sleep failed because at the time |
| * of the call there was no pending wakeup. |
| * |
| * @li ESYNCH_TIMEOUT means that the sleep timed out. |
| * |
| * @li ESYNCH_INTERRUPTED means that somebody interrupted the sleeping thread. |
| * |
| * @li ESYNCH_OK_ATOMIC means that the sleep succeeded and that there was |
| * a pending wakeup at the time of the call. The caller was not put |
| * asleep at all. |
| * |
| * @li ESYNCH_OK_BLOCKED means that the sleep succeeded; the full sleep was |
| * attempted. |
| */ |
| int waitq_sleep_timeout(waitq_t *wq, uint32_t usec, int flags) |
| { |
| ipl_t ipl; |
| int rc; |
| ipl = waitq_sleep_prepare(wq); |
| rc = waitq_sleep_timeout_unsafe(wq, usec, flags); |
| waitq_sleep_finish(wq, rc, ipl); |
| return rc; |
| } |
| /** Prepare to sleep in a waitq. |
| * |
| * This function will return holding the lock of the wait queue |
| * and interrupts disabled. |
| * |
| * @param wq Wait queue. |
| * |
| * @return Interrupt level as it existed on entry to this function. |
| */ |
| ipl_t waitq_sleep_prepare(waitq_t *wq) |
| { |
| ipl_t ipl; |
| restart: |
| ipl = interrupts_disable(); |
| if (THREAD) { /* needed during system initiailzation */ |
| /* |
| * Busy waiting for a delayed timeout. |
| * This is an important fix for the race condition between |
| * a delayed timeout and a next call to waitq_sleep_timeout(). |
| * Simply, the thread is not allowed to go to sleep if |
| * there are timeouts in progress. |
| */ |
| spinlock_lock(&THREAD->lock); |
| if (THREAD->timeout_pending) { |
| spinlock_unlock(&THREAD->lock); |
| interrupts_restore(ipl); |
| goto restart; |
| } |
| spinlock_unlock(&THREAD->lock); |
| } |
| spinlock_lock(&wq->lock); |
| return ipl; |
| } |
| /** Finish waiting in a wait queue. |
| * |
| * This function restores interrupts to the state that existed prior |
| * to the call to waitq_sleep_prepare(). If necessary, the wait queue |
| * lock is released. |
| * |
| * @param wq Wait queue. |
| * @param rc Return code of waitq_sleep_timeout_unsafe(). |
| * @param ipl Interrupt level returned by waitq_sleep_prepare(). |
| */ |
| void waitq_sleep_finish(waitq_t *wq, int rc, ipl_t ipl) |
| { |
| switch (rc) { |
| case ESYNCH_WOULD_BLOCK: |
| case ESYNCH_OK_ATOMIC: |
| spinlock_unlock(&wq->lock); |
| break; |
| default: |
| break; |
| } |
| interrupts_restore(ipl); |
| } |
| /** Internal implementation of waitq_sleep_timeout(). |
| * |
| * This function implements logic of sleeping in a wait queue. |
| * This call must be preceeded by a call to waitq_sleep_prepare() |
| * and followed by a call to waitq_slee_finish(). |
| * |
| * @param wq See waitq_sleep_timeout(). |
| * @param usec See waitq_sleep_timeout(). |
| * @param flags See waitq_sleep_timeout(). |
| * |
| * @return See waitq_sleep_timeout(). |
| */ |
| int waitq_sleep_timeout_unsafe(waitq_t *wq, uint32_t usec, int flags) |
| { |
| /* checks whether to go to sleep at all */ |
| if (wq->missed_wakeups) { |
| wq->missed_wakeups--; |
| return ESYNCH_OK_ATOMIC; |
| } |
| else { |
| if ((flags & SYNCH_FLAGS_NON_BLOCKING) && (usec == 0)) { |
| /* return immediatelly instead of going to sleep */ |
| return ESYNCH_WOULD_BLOCK; |
| } |
| } |
| /* |
| * Now we are firmly decided to go to sleep. |
| */ |
| spinlock_lock(&THREAD->lock); |
| if (flags & SYNCH_FLAGS_INTERRUPTIBLE) { |
| /* |
| * If the thread was already interrupted, |
| * don't go to sleep at all. |
| */ |
| if (THREAD->interrupted) { |
| spinlock_unlock(&THREAD->lock); |
| spinlock_unlock(&wq->lock); |
| return ESYNCH_INTERRUPTED; |
| } |
| /* |
| * Set context that will be restored if the sleep |
| * of this thread is ever interrupted. |
| */ |
| THREAD->sleep_interruptible = true; |
| if (!context_save(&THREAD->sleep_interruption_context)) { |
| /* Short emulation of scheduler() return code. */ |
| spinlock_unlock(&THREAD->lock); |
| return ESYNCH_INTERRUPTED; |
| } |
| } else { |
| THREAD->sleep_interruptible = false; |
| } |
| if (usec) { |
| /* We use the timeout variant. */ |
| if (!context_save(&THREAD->sleep_timeout_context)) { |
| /* Short emulation of scheduler() return code. */ |
| spinlock_unlock(&THREAD->lock); |
| return ESYNCH_TIMEOUT; |
| } |
| THREAD->timeout_pending = true; |
| timeout_register(&THREAD->sleep_timeout, (uint64_t) usec, waitq_timeouted_sleep, THREAD); |
| } |
| list_append(&THREAD->wq_link, &wq->head); |
| /* |
| * Suspend execution. |
| */ |
| THREAD->state = Sleeping; |
| THREAD->sleep_queue = wq; |
| spinlock_unlock(&THREAD->lock); |
| scheduler(); /* wq->lock is released in scheduler_separated_stack() */ |
| return ESYNCH_OK_BLOCKED; |
| } |
| /** Wake up first thread sleeping in a wait queue |
| * |
| * Wake up first thread sleeping in a wait queue. |
| * This is the SMP- and IRQ-safe wrapper meant for |
| * general use. |
| * |
| * Besides its 'normal' wakeup operation, it attempts |
| * to unregister possible timeout. |
| * |
| * @param wq Pointer to wait queue. |
| * @param all If this is non-zero, all sleeping threads |
| * will be woken up and missed count will be zeroed. |
| */ |
| void waitq_wakeup(waitq_t *wq, bool all) |
| { |
| ipl_t ipl; |
| ipl = interrupts_disable(); |
| spinlock_lock(&wq->lock); |
| _waitq_wakeup_unsafe(wq, all); |
| spinlock_unlock(&wq->lock); |
| interrupts_restore(ipl); |
| } |
| /** Internal SMP- and IRQ-unsafe version of waitq_wakeup() |
| * |
| * This is the internal SMP- and IRQ-unsafe version |
| * of waitq_wakeup(). It assumes wq->lock is already |
| * locked and interrupts are already disabled. |
| * |
| * @param wq Pointer to wait queue. |
| * @param all If this is non-zero, all sleeping threads |
| * will be woken up and missed count will be zeroed. |
| */ |
| void _waitq_wakeup_unsafe(waitq_t *wq, bool all) |
| { |
| thread_t *t; |
| loop: |
| if (list_empty(&wq->head)) { |
| wq->missed_wakeups++; |
| if (all) |
| wq->missed_wakeups = 0; |
| return; |
| } |
| t = list_get_instance(wq->head.next, thread_t, wq_link); |
| /* |
| * Lock the thread prior to removing it from the wq. |
| * This is not necessary because of mutual exclusion |
| * (the link belongs to the wait queue), but because |
| * of synchronization with waitq_timeouted_sleep() |
| * and waitq_interrupt_sleep(). |
| * |
| * In order for these two functions to work, the following |
| * invariant must hold: |
| * |
| * t->sleep_queue != NULL <=> t sleeps in a wait queue |
| * |
| * For an observer who locks the thread, the invariant |
| * holds only when the lock is held prior to removing |
| * it from the wait queue. |
| */ |
| spinlock_lock(&t->lock); |
| list_remove(&t->wq_link); |
| if (t->timeout_pending && timeout_unregister(&t->sleep_timeout)) |
| t->timeout_pending = false; |
| t->sleep_queue = NULL; |
| spinlock_unlock(&t->lock); |
| thread_ready(t); |
| if (all) |
| goto loop; |
| } |
| /** @} |
| */ |
| /trunk/kernel/generic/src/synch/futex.c |
|---|
| 0,0 → 1,339 |
| /* |
| * Copyright (C) 2006 Jakub Jermar |
| * All rights reserved. |
| * |
| * Redistribution and use in source and binary forms, with or without |
| * modification, are permitted provided that the following conditions |
| * are met: |
| * |
| * - Redistributions of source code must retain the above copyright |
| * notice, this list of conditions and the following disclaimer. |
| * - Redistributions in binary form must reproduce the above copyright |
| * notice, this list of conditions and the following disclaimer in the |
| * documentation and/or other materials provided with the distribution. |
| * - The name of the author may not be used to endorse or promote products |
| * derived from this software without specific prior written permission. |
| * |
| * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR |
| * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES |
| * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. |
| * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, |
| * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT |
| * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, |
| * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY |
| * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT |
| * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF |
| * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
| */ |
| /** @addtogroup sync |
| * @{ |
| */ |
| /** |
| * @file |
| * @brief Kernel backend for futexes. |
| */ |
| #include <synch/futex.h> |
| #include <synch/rwlock.h> |
| #include <synch/spinlock.h> |
| #include <synch/synch.h> |
| #include <mm/frame.h> |
| #include <mm/page.h> |
| #include <mm/slab.h> |
| #include <proc/thread.h> |
| #include <proc/task.h> |
| #include <genarch/mm/page_pt.h> |
| #include <genarch/mm/page_ht.h> |
| #include <adt/hash_table.h> |
| #include <adt/list.h> |
| #include <arch.h> |
| #include <align.h> |
| #include <panic.h> |
| #include <errno.h> |
| #include <print.h> |
| #define FUTEX_HT_SIZE 1024 /* keep it a power of 2 */ |
| static void futex_initialize(futex_t *futex); |
| static futex_t *futex_find(uintptr_t paddr); |
| static index_t futex_ht_hash(unative_t *key); |
| static bool futex_ht_compare(unative_t *key, count_t keys, link_t *item); |
| static void futex_ht_remove_callback(link_t *item); |
| /** |
| * Read-write lock protecting global futex hash table. |
| * It is also used to serialize access to all futex_t structures. |
| * Must be acquired before the task futex B+tree lock. |
| */ |
| static rwlock_t futex_ht_lock; |
| /** Futex hash table. */ |
| static hash_table_t futex_ht; |
| /** Futex hash table operations. */ |
| static hash_table_operations_t futex_ht_ops = { |
| .hash = futex_ht_hash, |
| .compare = futex_ht_compare, |
| .remove_callback = futex_ht_remove_callback |
| }; |
| /** Initialize futex subsystem. */ |
| void futex_init(void) |
| { |
| rwlock_initialize(&futex_ht_lock); |
| hash_table_create(&futex_ht, FUTEX_HT_SIZE, 1, &futex_ht_ops); |
| } |
| /** Initialize kernel futex structure. |
| * |
| * @param futex Kernel futex structure. |
| */ |
| void futex_initialize(futex_t *futex) |
| { |
| waitq_initialize(&futex->wq); |
| link_initialize(&futex->ht_link); |
| futex->paddr = 0; |
| futex->refcount = 1; |
| } |
| /** Sleep in futex wait queue. |
| * |
| * @param uaddr Userspace address of the futex counter. |
| * @param usec If non-zero, number of microseconds this thread is willing to sleep. |
| * @param flags Select mode of operation. |
| * |
| * @return One of ESYNCH_TIMEOUT, ESYNCH_OK_ATOMIC and ESYNCH_OK_BLOCKED. See synch.h. |
| * If there is no physical mapping for uaddr ENOENT is returned. |
| */ |
| unative_t sys_futex_sleep_timeout(uintptr_t uaddr, uint32_t usec, int flags) |
| { |
| futex_t *futex; |
| uintptr_t paddr; |
| pte_t *t; |
| ipl_t ipl; |
| ipl = interrupts_disable(); |
| /* |
| * Find physical address of futex counter. |
| */ |
| page_table_lock(AS, true); |
| t = page_mapping_find(AS, ALIGN_DOWN(uaddr, PAGE_SIZE)); |
| if (!t || !PTE_VALID(t) || !PTE_PRESENT(t)) { |
| page_table_unlock(AS, true); |
| interrupts_restore(ipl); |
| return (unative_t) ENOENT; |
| } |
| paddr = PTE_GET_FRAME(t) + (uaddr - ALIGN_DOWN(uaddr, PAGE_SIZE)); |
| page_table_unlock(AS, true); |
| interrupts_restore(ipl); |
| futex = futex_find(paddr); |
| return (unative_t) waitq_sleep_timeout(&futex->wq, usec, flags | SYNCH_FLAGS_INTERRUPTIBLE); |
| } |
| /** Wakeup one thread waiting in futex wait queue. |
| * |
| * @param uaddr Userspace address of the futex counter. |
| * |
| * @return ENOENT if there is no physical mapping for uaddr. |
| */ |
| unative_t sys_futex_wakeup(uintptr_t uaddr) |
| { |
| futex_t *futex; |
| uintptr_t paddr; |
| pte_t *t; |
| ipl_t ipl; |
| ipl = interrupts_disable(); |
| /* |
| * Find physical address of futex counter. |
| */ |
| page_table_lock(AS, true); |
| t = page_mapping_find(AS, ALIGN_DOWN(uaddr, PAGE_SIZE)); |
| if (!t || !PTE_VALID(t) || !PTE_PRESENT(t)) { |
| page_table_unlock(AS, true); |
| interrupts_restore(ipl); |
| return (unative_t) ENOENT; |
| } |
| paddr = PTE_GET_FRAME(t) + (uaddr - ALIGN_DOWN(uaddr, PAGE_SIZE)); |
| page_table_unlock(AS, true); |
| interrupts_restore(ipl); |
| futex = futex_find(paddr); |
| waitq_wakeup(&futex->wq, WAKEUP_FIRST); |
| return 0; |
| } |
| /** Find kernel address of the futex structure corresponding to paddr. |
| * |
| * If the structure does not exist already, a new one is created. |
| * |
| * @param paddr Physical address of the userspace futex counter. |
| * |
| * @return Address of the kernel futex structure. |
| */ |
| futex_t *futex_find(uintptr_t paddr) |
| { |
| link_t *item; |
| futex_t *futex; |
| btree_node_t *leaf; |
| /* |
| * Find the respective futex structure |
| * or allocate new one if it does not exist already. |
| */ |
| rwlock_read_lock(&futex_ht_lock); |
| item = hash_table_find(&futex_ht, &paddr); |
| if (item) { |
| futex = hash_table_get_instance(item, futex_t, ht_link); |
| /* |
| * See if the current task knows this futex. |
| */ |
| mutex_lock(&TASK->futexes_lock); |
| if (!btree_search(&TASK->futexes, paddr, &leaf)) { |
| /* |
| * The futex is new to the current task. |
| * However, we only have read access. |
| * Gain write access and try again. |
| */ |
| mutex_unlock(&TASK->futexes_lock); |
| goto gain_write_access; |
| } |
| mutex_unlock(&TASK->futexes_lock); |
| rwlock_read_unlock(&futex_ht_lock); |
| } else { |
| gain_write_access: |
| /* |
| * Upgrade to writer is not currently supported, |
| * therefore, it is necessary to release the read lock |
| * and reacquire it as a writer. |
| */ |
| rwlock_read_unlock(&futex_ht_lock); |
| rwlock_write_lock(&futex_ht_lock); |
| /* |
| * Avoid possible race condition by searching |
| * the hash table once again with write access. |
| */ |
| item = hash_table_find(&futex_ht, &paddr); |
| if (item) { |
| futex = hash_table_get_instance(item, futex_t, ht_link); |
| /* |
| * See if this futex is known to the current task. |
| */ |
| mutex_lock(&TASK->futexes_lock); |
| if (!btree_search(&TASK->futexes, paddr, &leaf)) { |
| /* |
| * The futex is new to the current task. |
| * Upgrade its reference count and put it to the |
| * current task's B+tree of known futexes. |
| */ |
| futex->refcount++; |
| btree_insert(&TASK->futexes, paddr, futex, leaf); |
| } |
| mutex_unlock(&TASK->futexes_lock); |
| rwlock_write_unlock(&futex_ht_lock); |
| } else { |
| futex = (futex_t *) malloc(sizeof(futex_t), 0); |
| futex_initialize(futex); |
| futex->paddr = paddr; |
| hash_table_insert(&futex_ht, &paddr, &futex->ht_link); |
| /* |
| * This is the first task referencing the futex. |
| * It can be directly inserted into its |
| * B+tree of known futexes. |
| */ |
| mutex_lock(&TASK->futexes_lock); |
| btree_insert(&TASK->futexes, paddr, futex, NULL); |
| mutex_unlock(&TASK->futexes_lock); |
| rwlock_write_unlock(&futex_ht_lock); |
| } |
| } |
| return futex; |
| } |
| /** Compute hash index into futex hash table. |
| * |
| * @param key Address where the key (i.e. physical address of futex counter) is stored. |
| * |
| * @return Index into futex hash table. |
| */ |
| index_t futex_ht_hash(unative_t *key) |
| { |
| return *key & (FUTEX_HT_SIZE-1); |
| } |
| /** Compare futex hash table item with a key. |
| * |
| * @param key Address where the key (i.e. physical address of futex counter) is stored. |
| * |
| * @return True if the item matches the key. False otherwise. |
| */ |
| bool futex_ht_compare(unative_t *key, count_t keys, link_t *item) |
| { |
| futex_t *futex; |
| ASSERT(keys == 1); |
| futex = hash_table_get_instance(item, futex_t, ht_link); |
| return *key == futex->paddr; |
| } |
| /** Callback for removal items from futex hash table. |
| * |
| * @param item Item removed from the hash table. |
| */ |
| void futex_ht_remove_callback(link_t *item) |
| { |
| futex_t *futex; |
| futex = hash_table_get_instance(item, futex_t, ht_link); |
| free(futex); |
| } |
| /** Remove references from futexes known to the current task. */ |
| void futex_cleanup(void) |
| { |
| link_t *cur; |
| rwlock_write_lock(&futex_ht_lock); |
| mutex_lock(&TASK->futexes_lock); |
| for (cur = TASK->futexes.leaf_head.next; cur != &TASK->futexes.leaf_head; cur = cur->next) { |
| btree_node_t *node; |
| int i; |
| node = list_get_instance(cur, btree_node_t, leaf_link); |
| for (i = 0; i < node->keys; i++) { |
| futex_t *ftx; |
| uintptr_t paddr = node->key[i]; |
| ftx = (futex_t *) node->value[i]; |
| if (--ftx->refcount == 0) |
| hash_table_remove(&futex_ht, &paddr, 1); |
| } |
| } |
| mutex_unlock(&TASK->futexes_lock); |
| rwlock_write_unlock(&futex_ht_lock); |
| } |
| /** @} |
| */ |
| /trunk/kernel/generic/src/synch/condvar.c |
|---|
| 0,0 → 1,108 |
| /* |
| * Copyright (C) 2001-2004 Jakub Jermar |
| * All rights reserved. |
| * |
| * Redistribution and use in source and binary forms, with or without |
| * modification, are permitted provided that the following conditions |
| * are met: |
| * |
| * - Redistributions of source code must retain the above copyright |
| * notice, this list of conditions and the following disclaimer. |
| * - Redistributions in binary form must reproduce the above copyright |
| * notice, this list of conditions and the following disclaimer in the |
| * documentation and/or other materials provided with the distribution. |
| * - The name of the author may not be used to endorse or promote products |
| * derived from this software without specific prior written permission. |
| * |
| * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR |
| * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES |
| * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. |
| * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, |
| * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT |
| * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, |
| * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY |
| * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT |
| * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF |
| * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
| */ |
| /** @addtogroup sync |
| * @{ |
| */ |
| /** |
| * @file |
| * @brief Condition variables. |
| */ |
| #include <synch/condvar.h> |
| #include <synch/mutex.h> |
| #include <synch/waitq.h> |
| #include <synch/synch.h> |
| #include <arch.h> |
| #include <typedefs.h> |
| /** Initialize condition variable. |
| * |
| * @param cv Condition variable. |
| */ |
| void condvar_initialize(condvar_t *cv) |
| { |
| waitq_initialize(&cv->wq); |
| } |
| /** |
| * Signal the condition has become true |
| * to the first waiting thread by waking it up. |
| * |
| * @param cv Condition variable. |
| */ |
| void condvar_signal(condvar_t *cv) |
| { |
| waitq_wakeup(&cv->wq, WAKEUP_FIRST); |
| } |
| /** |
| * Signal the condition has become true |
| * to all waiting threads by waking them up. |
| * |
| * @param cv Condition variable. |
| */ |
| void condvar_broadcast(condvar_t *cv) |
| { |
| waitq_wakeup(&cv->wq, WAKEUP_ALL); |
| } |
| /** Wait for the condition becoming true. |
| * |
| * @param cv Condition variable. |
| * @param mtx Mutex. |
| * @param usec Timeout value in microseconds. |
| * @param flags Select mode of operation. |
| * |
| * For exact description of meaning of possible combinations |
| * of usec and flags, see comment for waitq_sleep_timeout(). |
| * Note that when SYNCH_FLAGS_NON_BLOCKING is specified here, |
| * ESYNCH_WOULD_BLOCK is always returned. |
| * |
| * @return See comment for waitq_sleep_timeout(). |
| */ |
| int _condvar_wait_timeout(condvar_t *cv, mutex_t *mtx, uint32_t usec, int flags) |
| { |
| int rc; |
| ipl_t ipl; |
| ipl = waitq_sleep_prepare(&cv->wq); |
| mutex_unlock(mtx); |
| cv->wq.missed_wakeups = 0; /* Enforce blocking. */ |
| rc = waitq_sleep_timeout_unsafe(&cv->wq, usec, flags); |
| mutex_lock(mtx); |
| waitq_sleep_finish(&cv->wq, rc, ipl); |
| return rc; |
| } |
| /** @} |
| */ |