__shmem_set_lock.c

/*
 * Copyright (c) 2016 U.S. Army Research laboratory. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * 1. Redistributions of source code must retain the above copyright notice,
 * this list of conditions and the following disclaimer.
 *
 * 2. 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.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "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 COPYRIGHT HOLDER OR CONTRIBUTORS 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.
 * 
 * This software was developed by Brown Deer Technology, LLC. with Copyright
 * assigned to the US Army Research laboratory as required by contract.
 */

#include "internals.h"
#include "shmem.h"

#ifdef __cplusplus
extern "C" {
#endif

SHMEM_SCOPE void
__shmem_set_lock (volatile long* x)
{
	__asm__ __volatile__(
		"mov r1, #0                \n" // zero lock pointer offset
		"mov r2, #1                \n" // copying value to write to lock
		".Loop%=:                  \n"
		"   testset r2, [%[x], r1] \n" // test set
		"   sub r3, r2, #0         \n" // checking result
		"   bne .Loop%=            \n" // if zero, loop until we acquire lock
		:
		: [x] "r" (x)
		: "r1", "r2", "r3"
	);
}

#ifdef __cplusplus
}
#endif