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Filename : atomic.stp
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// Atomic functions.
// Copyright (C) 2010 Red Hat Inc.
//
// This file is part of systemtap, and is free software.  You can
// redistribute it and/or modify it under the terms of the GNU General
// Public License (GPL); either version 2, or (at your option) any
// later version.

/**
 * sfunction atomic_read - Retrieves an atomic variable from kernel memory
 *
 * @addr: pointer to atomic variable
 *
 * Safely perform the read of an atomic variable.
 */
function atomic_read:long(addr:long)
%{ /* pure */
	atomic_t *a = (atomic_t *)(uintptr_t)STAP_ARG_addr;

	/* We call deref() here to ensure the memory is valid to read.
	 * Note the result is thrown away, then we use the "real"
	 * atomic read function now that we know the address is safe. */
	(void)kderef(sizeof(*a), a);
	STAP_RETVALUE = atomic_read(a);
	CATCH_DEREF_FAULT();
%}

/**
 * sfunction atomic_long_read - Retrieves an atomic long variable from kernel memory
 *
 * @addr: pointer to atomic long variable
 *
 * Safely perform the read of an atomic long variable. This will be a
 * NOP on kernels that do not have ATOMIC_LONG_INIT set on the kernel config.
 */
function atomic_long_read:long(addr:long)
%{ /* pure */
#ifdef ATOMIC_LONG_INIT
	atomic_long_t *a = (atomic_long_t *)(uintptr_t)STAP_ARG_addr;

	/* We call deref() here to ensure the memory is valid to read.
	 * Note the result is thrown away, then we use the "real"
	 * atomic read function now that we know the address is safe. */
	(void)kderef(sizeof(*a), a);
	STAP_RETVALUE = atomic_long_read(a);
	CATCH_DEREF_FAULT();
#endif
%}