futex.h

/* SPDX-License-Identifier: GPL-2.0 */
/*
 * Glibc independent futex library for testing kernel functionality.
 * Shamelessly stolen from Darren Hart <[email protected]>
 *    http://git.kernel.org/cgit/linux/kernel/git/dvhart/futextest.git/
 */

#ifndef _FUTEX_H
#define _FUTEX_H

#include <stdbool.h>
#include <unistd.h>
#include <sys/syscall.h>
#include <sys/types.h>
#include <linux/futex.h>

struct bench_futex_parameters {
	bool silent;
	bool fshared;
	bool mlockall;
	bool multi; /* lock-pi */
	bool pi; /* requeue-pi */
	bool broadcast; /* requeue */
	unsigned int runtime; /* seconds*/
	unsigned int nthreads;
	unsigned int nfutexes;
	unsigned int nwakes;
	unsigned int nrequeue;
	int nbuckets;
};

/**
 * futex_syscall() - SYS_futex syscall wrapper
 * @uaddr:	address of first futex
 * @op:		futex op code
 * @val:	typically expected value of uaddr, but varies by op
 * @timeout:	typically an absolute struct timespec (except where noted
 *		otherwise). Overloaded by some ops
 * @uaddr2:	address of second futex for some ops
 * @val3:	varies by op
 * @opflags:	flags to be bitwise OR'd with op, such as FUTEX_PRIVATE_FLAG
 *
 * futex_syscall() is used by all the following futex op wrappers. It can also be
 * used for misuse and abuse testing. Generally, the specific op wrappers
 * should be used instead.
 *
 * These argument descriptions are the defaults for all
 * like-named arguments in the following wrappers except where noted below.
 */
static inline int
futex_syscall(volatile u_int32_t *uaddr, int op, u_int32_t val, struct timespec *timeout,
	      volatile u_int32_t *uaddr2, int val3, int opflags)
{
	return syscall(SYS_futex, uaddr, op | opflags, val, timeout, uaddr2, val3);
}

static inline int
futex_syscall_nr_requeue(volatile u_int32_t *uaddr, int op, u_int32_t val, int nr_requeue,
			 volatile u_int32_t *uaddr2, int val3, int opflags)
{
	return syscall(SYS_futex, uaddr, op | opflags, val, nr_requeue, uaddr2, val3);
}

/**
 * futex_wait() - block on uaddr with optional timeout
 * @timeout:	relative timeout
 */
static inline int
futex_wait(u_int32_t *uaddr, u_int32_t val, struct timespec *timeout, int opflags)
{
	return futex_syscall(uaddr, FUTEX_WAIT, val, timeout, NULL, 0, opflags);
}

/**
 * futex_wake() - wake one or more tasks blocked on uaddr
 * @nr_wake:	wake up to this many tasks
 */
static inline int
futex_wake(u_int32_t *uaddr, int nr_wake, int opflags)
{
	return futex_syscall(uaddr, FUTEX_WAKE, nr_wake, NULL, NULL, 0, opflags);
}

/**
 * futex_lock_pi() - block on uaddr as a PI mutex
 */
static inline int
futex_lock_pi(u_int32_t *uaddr, struct timespec *timeout, int opflags)
{
	return futex_syscall(uaddr, FUTEX_LOCK_PI, 0, timeout, NULL, 0, opflags);
}

/**
 * futex_unlock_pi() - release uaddr as a PI mutex, waking the top waiter
 */
static inline int
futex_unlock_pi(u_int32_t *uaddr, int opflags)
{
	return futex_syscall(uaddr, FUTEX_UNLOCK_PI, 0, NULL, NULL, 0, opflags);
}

/**
* futex_cmp_requeue() - requeue tasks from uaddr to uaddr2
* @nr_wake:        wake up to this many tasks
* @nr_requeue:     requeue up to this many tasks
*/
static inline int
futex_cmp_requeue(u_int32_t *uaddr, u_int32_t val, u_int32_t *uaddr2, int nr_wake,
		 int nr_requeue, int opflags)
{
	return futex_syscall_nr_requeue(uaddr, FUTEX_CMP_REQUEUE, nr_wake, nr_requeue, uaddr2,
					val, opflags);
}

/**
 * futex_wait_requeue_pi() - block on uaddr and prepare to requeue to uaddr2
 * @uaddr:	non-PI futex source
 * @uaddr2:	PI futex target
 *
 * This is the first half of the requeue_pi mechanism. It shall always be
 * paired with futex_cmp_requeue_pi().
 */
static inline int
futex_wait_requeue_pi(u_int32_t *uaddr, u_int32_t val, u_int32_t *uaddr2,
		      struct timespec *timeout, int opflags)
{
	return futex_syscall(uaddr, FUTEX_WAIT_REQUEUE_PI, val, timeout, uaddr2, 0,
			     opflags);
}

/**
 * futex_cmp_requeue_pi() - requeue tasks from uaddr to uaddr2
 * @uaddr:	non-PI futex source
 * @uaddr2:	PI futex target
 * @nr_requeue:	requeue up to this many tasks
 *
 * This is the second half of the requeue_pi mechanism. It shall always be
 * paired with futex_wait_requeue_pi(). The first waker is always awoken.
 */
static inline int
futex_cmp_requeue_pi(u_int32_t *uaddr, u_int32_t val, u_int32_t *uaddr2,
		     int nr_requeue, int opflags)
{
	return futex_syscall_nr_requeue(uaddr, FUTEX_CMP_REQUEUE_PI, 1, nr_requeue, uaddr2,
					val, opflags);
}

void futex_set_nbuckets_param(struct bench_futex_parameters *params);
void futex_print_nbuckets(struct bench_futex_parameters *params);

#endif /* _FUTEX_H */