diff options
Diffstat (limited to 'sos-code-article6.75/sos/ksynch.c')
| -rw-r--r-- | sos-code-article6.75/sos/ksynch.c | 235 |
1 files changed, 235 insertions, 0 deletions
diff --git a/sos-code-article6.75/sos/ksynch.c b/sos-code-article6.75/sos/ksynch.c new file mode 100644 index 0000000..edbd800 --- /dev/null +++ b/sos-code-article6.75/sos/ksynch.c @@ -0,0 +1,235 @@ +/* Copyright (C) 2004 David Decotigny + + 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 the Free Software Foundation; either version 2 + of the License, or (at your option) any later version. + + This program is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + GNU General Public License for more details. + + You should have received a copy of the GNU General Public License + along with this program; if not, write to the Free Software + Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, + USA. +*/ + + +#include <hwcore/irq.h> + + +#include "ksynch.h" + + +sos_ret_t sos_ksema_init(struct sos_ksema *sema, const char *name, + int initial_value, + sos_kwaitq_ordering_t ordering) +{ + sema->value = initial_value; + return sos_kwaitq_init(& sema->kwaitq, name, ordering); +} + + +sos_ret_t sos_ksema_dispose(struct sos_ksema *sema) +{ + return sos_kwaitq_dispose(& sema->kwaitq); +} + + +sos_ret_t sos_ksema_down(struct sos_ksema *sema, + struct sos_time *timeout) +{ + sos_ui32_t flags; + sos_ret_t retval; + + sos_disable_IRQs(flags); + retval = SOS_OK; + + sema->value --; + if (sema->value < 0) + { + /* Wait for somebody to wake us */ + retval = sos_kwaitq_wait(& sema->kwaitq, timeout); + + /* Something wrong happened (timeout, external wakeup, ...) ? */ + if (SOS_OK != retval) + { + /* Yes: pretend we did not ask for the semaphore */ + sema->value ++; + } + } + + sos_restore_IRQs(flags); + return retval; +} + + +sos_ret_t sos_ksema_trydown(struct sos_ksema *sema) +{ + sos_ui32_t flags; + sos_ret_t retval; + + sos_disable_IRQs(flags); + + /* Can we take the semaphore without blocking ? */ + if (sema->value >= 1) + { + /* Yes: we take it now */ + sema->value --; + retval = SOS_OK; + } + else + { + /* No: we signal it */ + retval = -SOS_EBUSY; + } + + sos_restore_IRQs(flags); + return retval; +} + + +sos_ret_t sos_ksema_up(struct sos_ksema *sema) +{ + sos_ui32_t flags; + sos_ret_t retval; + + sos_disable_IRQs(flags); + + sema->value ++; + retval = sos_kwaitq_wakeup(& sema->kwaitq, 1, SOS_OK); + + sos_restore_IRQs(flags); + return retval; +} + + +sos_ret_t sos_kmutex_init(struct sos_kmutex *mutex, const char *name, + sos_kwaitq_ordering_t ordering) +{ + mutex->owner = NULL; + return sos_kwaitq_init(& mutex->kwaitq, name, ordering); +} + + +sos_ret_t sos_kmutex_dispose(struct sos_kmutex *mutex) +{ + return sos_kwaitq_dispose(& mutex->kwaitq); +} + + +/* + * Implementation based on ownership transfer (ie no while() + * loop). The only assumption is that the thread awoken by + * kmutex_unlock is not suppressed before effectively waking up: in + * that case the mutex will be forever locked AND unlockable (by + * nobody other than the owner, but this is not natural since this + * owner already issued an unlock()...). The same problem happens with + * the semaphores, but in a less obvious manner. + */ +sos_ret_t sos_kmutex_lock(struct sos_kmutex *mutex, + struct sos_time *timeout) +{ + __label__ exit_kmutex_lock; + sos_ui32_t flags; + sos_ret_t retval; + + sos_disable_IRQs(flags); + retval = SOS_OK; + + /* Mutex already owned ? */ + if (NULL != mutex->owner) + { + /* Owned by us or by someone else ? */ + if (sos_thread_get_current() == mutex->owner) + { + /* Owned by us: do nothing */ + retval = -SOS_EBUSY; + goto exit_kmutex_lock; + } + + /* Wait for somebody to wake us */ + retval = sos_kwaitq_wait(& mutex->kwaitq, timeout); + + /* Something wrong happened ? */ + if (SOS_OK != retval) + { + goto exit_kmutex_lock; + } + } + + /* Ok, the mutex is available to us: take it */ + mutex->owner = sos_thread_get_current(); + + exit_kmutex_lock: + sos_restore_IRQs(flags); + return retval; +} + + +sos_ret_t sos_kmutex_trylock(struct sos_kmutex *mutex) +{ + sos_ui32_t flags; + sos_ret_t retval; + + sos_disable_IRQs(flags); + + /* Mutex available to us ? */ + if (NULL == mutex->owner) + { + /* Great ! Take it now */ + mutex->owner = sos_thread_get_current(); + + retval = SOS_OK; + } + else + { + /* No: signal it */ + retval = -SOS_EBUSY; + } + + sos_restore_IRQs(flags); + return retval; +} + + +sos_ret_t sos_kmutex_unlock(struct sos_kmutex *mutex) +{ + sos_ui32_t flags; + sos_ret_t retval; + + sos_disable_IRQs(flags); + + if (sos_thread_get_current() != mutex->owner) + retval = -SOS_EPERM; + + else if (sos_kwaitq_is_empty(& mutex->kwaitq)) + { + /* + * There is NOT ANY thread waiting => we really mark the mutex + * as FREE + */ + mutex->owner = NULL; + retval = SOS_OK; + } + else + { + /* + * There is at least 1 thread waiting => we DO NOT mark the + * mutex as free ! + * Actually, we should have written: + * mutex->owner = thread_that_is_woken_up; + * But the real Id of the next thread owning the mutex is not + * that important. What is important here is that mutex->owner + * IS NOT NULL. Otherwise there will be a possibility for the + * thread woken up here to have the mutex stolen by a thread + * locking the mutex in the meantime. + */ + retval = sos_kwaitq_wakeup(& mutex->kwaitq, 1, SOS_OK); + } + + sos_restore_IRQs(flags); + return retval; +} |