/*      $NetBSD: pthread_lock.c,v 1.36 2022/04/10 10:38:33 riastradh Exp $      */

/*-
* Copyright (c) 2001, 2006, 2007 The NetBSD Foundation, Inc.
* All rights reserved.
*
* This code is derived from software contributed to The NetBSD Foundation
* by Nathan J. Williams and Andrew Doran.
*
* 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 NETBSD FOUNDATION, INC. 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 FOUNDATION 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.
*/

/*
* libpthread internal spinlock routines.
*/

#include <sys/cdefs.h>
__RCSID("$NetBSD: pthread_lock.c,v 1.36 2022/04/10 10:38:33 riastradh Exp $");

/* Need to use libc-private names for atomic operations. */
#include "../../common/lib/libc/atomic/atomic_op_namespace.h"

#include <sys/types.h>
#include <sys/ras.h>

#include <machine/lock.h>

#include <errno.h>
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>

#include "pthread.h"
#include "pthread_int.h"

/* How many times to try acquiring spin locks on MP systems. */
#define PTHREAD__NSPINS         64

RAS_DECL(pthread__lock);

static void     pthread__spinlock_slow(pthread_spin_t *);

#ifdef PTHREAD__ASM_RASOPS

void pthread__ras_simple_lock_init(__cpu_simple_lock_t *);
int pthread__ras_simple_lock_try(__cpu_simple_lock_t *);
void pthread__ras_simple_unlock(__cpu_simple_lock_t *);

#else

static void
pthread__ras_simple_lock_init(__cpu_simple_lock_t *alp)
{

       __cpu_simple_lock_clear(alp);
}

static int
pthread__ras_simple_lock_try(__cpu_simple_lock_t *alp)
{
       int locked;

       RAS_START(pthread__lock);
       locked = __SIMPLELOCK_LOCKED_P(alp);
       __cpu_simple_lock_set(alp);
       RAS_END(pthread__lock);

       return !locked;
}

static void
pthread__ras_simple_unlock(__cpu_simple_lock_t *alp)
{

       __cpu_simple_lock_clear(alp);
}

#endif /* PTHREAD__ASM_RASOPS */

static const struct pthread_lock_ops pthread__lock_ops_ras = {
       pthread__ras_simple_lock_init,
       pthread__ras_simple_lock_try,
       pthread__ras_simple_unlock,
       pthread__spinlock_slow,
};

static void
pthread__atomic_simple_lock_init(__cpu_simple_lock_t *alp)
{

       __cpu_simple_lock_init(alp);
}

static int
pthread__atomic_simple_lock_try(__cpu_simple_lock_t *alp)
{

       return (__cpu_simple_lock_try(alp));
}

static void
pthread__atomic_simple_unlock(__cpu_simple_lock_t *alp)
{

       __cpu_simple_unlock(alp);
}

static const struct pthread_lock_ops pthread__lock_ops_atomic = {
       pthread__atomic_simple_lock_init,
       pthread__atomic_simple_lock_try,
       pthread__atomic_simple_unlock,
       pthread__spinlock_slow,
};

/*
* We default to pointing to the RAS primitives; we might need to use
* locks early, but before main() starts.  This is safe, since no other
* threads will be active for the process, so atomicity will not be
* required.
*/
const struct pthread_lock_ops *pthread__lock_ops = &pthread__lock_ops_ras;

/*
* Prevent this routine from being inlined.  The common case is no
* contention and it's better to not burden the instruction decoder.
*/
static void
pthread__spinlock_slow(pthread_spin_t *lock)
{
       pthread_t self;
       int count;

       self = pthread__self();

       do {
               count = pthread__nspins;
               while (__SIMPLELOCK_LOCKED_P(lock) && --count > 0)
                       pthread__smt_pause();
               if (count > 0) {
                       if ((*self->pt_lockops.plo_try)(lock))
                               break;
                       continue;
               }
               sched_yield();
       } while (/*CONSTCOND*/ 1);
}

/*
* Initialize the locking primitives.  On uniprocessors, we always
* use Restartable Atomic Sequences if they are available.  Otherwise,
* we fall back onto machine-dependent atomic lock primitives.
*/
void
pthread__lockprim_init(void)
{
       char *p;

       if ((p = pthread__getenv("PTHREAD_NSPINS")) != NULL)
               pthread__nspins = atoi(p);
       else if (pthread__concurrency != 1)
               pthread__nspins = PTHREAD__NSPINS;
       else
               pthread__nspins = 1;

       if (pthread__concurrency != 1) {
               pthread__lock_ops = &pthread__lock_ops_atomic;
               return;
       }

       if (rasctl(RAS_ADDR(pthread__lock), RAS_SIZE(pthread__lock),
           RAS_INSTALL) != 0) {
               pthread__lock_ops = &pthread__lock_ops_atomic;
               return;
       }
}

void
pthread_lockinit(pthread_spin_t *lock)
{

       pthread__simple_lock_init(lock);
}