diff options
Diffstat (limited to 'kern/semaphore_i.h')
-rw-r--r-- | kern/semaphore_i.h | 60 |
1 files changed, 60 insertions, 0 deletions
diff --git a/kern/semaphore_i.h b/kern/semaphore_i.h new file mode 100644 index 0000000..c6769c1 --- /dev/null +++ b/kern/semaphore_i.h @@ -0,0 +1,60 @@ +/* + * Copyright (c) 2017 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 + * the Free Software Foundation, either version 3 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, see <http://www.gnu.org/licenses/>. + */ + +#ifndef _KERN_SEMAPHORE_I_H +#define _KERN_SEMAPHORE_I_H + +#include <kern/assert.h> +#include <machine/atomic.h> + +struct semaphore { + unsigned int value; +}; + +static inline unsigned int +semaphore_dec(struct semaphore *semaphore) +{ + unsigned int prev, value; + + do { + value = semaphore->value; + + if (value == 0) { + break; + } + + prev = atomic_cas_uint(&semaphore->value, value, value - 1); + } while (prev != value); + + return value; +} + +static inline unsigned int +semaphore_inc(struct semaphore *semaphore) +{ + unsigned int prev; + + prev = atomic_fetchadd_uint(&semaphore->value, 1); + assert(prev != SEMAPHORE_VALUE_MAX); + return prev; +} + +void semaphore_wait_slow(struct semaphore *semaphore); + +void semaphore_post_slow(struct semaphore *semaphore); + +#endif /* _KERN_SEMAPHORE_I_H */ |