musl/src/thread/pthread_barrier_init.c

#include "pthread_impl.h"

int pthread_barrier_init(pthread_barrier_t *restrict b, const pthread_barrierattr_t *restrict a, unsigned count)
{
	if (count-1 > INT_MAX-1) return EINVAL;
	*b = (pthread_barrier_t){ ._b_limit = count-1 | (a?*a:0) };
	return 0;
}
initial check-in, version 0.5.0 2011-02-12 00:22:29 -05:00			`#include "pthread_impl.h"`

use restrict everywhere it's required by c99 and/or posix 2008 to deal with the fact that the public headers may be used with pre-c99 compilers, __restrict is used in place of restrict, and defined appropriately for any supported compiler. we also avoid the form [restrict] since older versions of gcc rejected it due to a bug in the original c99 standard, and instead use the form *restrict. 2012-09-06 22:44:55 -04:00			`int pthread_barrier_init(pthread_barrier_t restrict b, const pthread_barrierattr_t restrict a, unsigned count)`
initial check-in, version 0.5.0 2011-02-12 00:22:29 -05:00			`{`
process-shared barrier support, based on discussion with bdonlan this implementation is rather heavy-weight, but it's the first solution i've found that's actually correct. all waiters actually wait twice at the barrier so that they can synchronize exit, and they hold a "vm lock" that prevents changes to virtual memory mappings (and blocks pthread_barrier_destroy) until all waiters are finished inspecting the barrier. thus, it is safe for any thread to destroy and/or unmap the barrier's memory as soon as pthread_barrier_wait returns, without further synchronization. 2011-09-27 13:50:29 -04:00			`if (count-1 > INT_MAX-1) return EINVAL;`
			`b = (pthread_barrier_t){ ._b_limit = count-1 \| (a?a:0) };`
initial check-in, version 0.5.0 2011-02-12 00:22:29 -05:00			`return 0;`
			`}`