// SPDX-License-Identifier: CDDL-1.0
/*
 * This file and its contents are supplied under the terms of the
 * Common Development and Distribution License ("CDDL"), version 1.0.
 * You may only use this file in accordance with the terms of version
 * 1.0 of the CDDL.
 *
 * A full copy of the text of the CDDL should have accompanied this
 * source.  A copy of the CDDL is also available via the Internet at
 * https://opensource.org/license/CDDL-1.0.
 */
/*
 * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
 * Copyright (c) 2012, 2018 by Delphix. All rights reserved.
 * Copyright (c) 2016 Actifio, Inc. All rights reserved.
 * Copyright (c) 2025, Klara, Inc.
 */

#include <assert.h>
#include <pthread.h>
#include <string.h>
#include <sys/thread.h>

/* this only exists to have its address taken */
void p0(void) {}

/*
 * =========================================================================
 * threads
 * =========================================================================
 *
 * TS_STACK_MIN is dictated by the minimum allowed pthread stack size.  While
 * TS_STACK_MAX is somewhat arbitrary, it was selected to be large enough for
 * the expected stack depth while small enough to avoid exhausting address
 * space with high thread counts.
 */
#define	TS_STACK_MIN	MAX(PTHREAD_STACK_MIN, 32768)
#define	TS_STACK_MAX	(256 * 1024)

struct zk_thread_wrapper {
	void (*func)(void *);
	void *arg;
};

static void *
zk_thread_wrapper(void *arg)
{
	struct zk_thread_wrapper ztw;
	memcpy(&ztw, arg, sizeof (ztw));
	free(arg);
	ztw.func(ztw.arg);
	return (NULL);
}

kthread_t *
zk_thread_create(const char *name, void (*func)(void *), void *arg,
    size_t stksize, int state)
{
	pthread_attr_t attr;
	pthread_t tid;
	char *stkstr;
	struct zk_thread_wrapper *ztw;
	int detachstate = PTHREAD_CREATE_DETACHED;

	VERIFY0(pthread_attr_init(&attr));

	if (state & TS_JOINABLE)
		detachstate = PTHREAD_CREATE_JOINABLE;

	VERIFY0(pthread_attr_setdetachstate(&attr, detachstate));

	/*
	 * We allow the default stack size in user space to be specified by
	 * setting the ZFS_STACK_SIZE environment variable.  This allows us
	 * the convenience of observing and debugging stack overruns in
	 * user space.  Explicitly specified stack sizes will be honored.
	 * The usage of ZFS_STACK_SIZE is discussed further in the
	 * ENVIRONMENT VARIABLES sections of the ztest(1) man page.
	 */
	if (stksize == 0) {
		stkstr = getenv("ZFS_STACK_SIZE");

		if (stkstr == NULL)
			stksize = TS_STACK_MAX;
		else
			stksize = MAX(atoi(stkstr), TS_STACK_MIN);
	}

	VERIFY3S(stksize, >, 0);
	stksize = P2ROUNDUP(MAX(stksize, TS_STACK_MIN), PAGESIZE);

	/*
	 * If this ever fails, it may be because the stack size is not a
	 * multiple of system page size.
	 */
	VERIFY0(pthread_attr_setstacksize(&attr, stksize));
	VERIFY0(pthread_attr_setguardsize(&attr, PAGESIZE));

	VERIFY(ztw = malloc(sizeof (*ztw)));
	ztw->func = func;
	ztw->arg = arg;
	VERIFY0(pthread_create(&tid, &attr, zk_thread_wrapper, ztw));
	VERIFY0(pthread_attr_destroy(&attr));

	pthread_setname_np(tid, name);

	return ((void *)(uintptr_t)tid);
}