/*
 * Copyright (c) 2005, David Xu <davidxu@freebsd.org>
 * 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 unmodified, 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 AUTHOR ``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 AUTHOR 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.
 *
 * $FreeBSD$
 */

#include "namespace.h"
#include <sys/param.h>
#include <sys/types.h>
#include <sys/signalvar.h>
#include <signal.h>
#include <errno.h>
#include <fcntl.h>
#include <unistd.h>
#include <string.h>
#include <pthread.h>
#include "un-namespace.h"

#include "thr_private.h"

/* #define DEBUG_SIGNAL */
#ifdef DEBUG_SIGNAL
#define DBG_MSG		stdout_debug
#else
#define DBG_MSG(x...)
#endif

extern int	__pause(void);
int	___pause(void);
int	_raise(int);
int	__sigtimedwait(const sigset_t *set, siginfo_t *info,
	const struct timespec * timeout);
int	_sigtimedwait(const sigset_t *set, siginfo_t *info,
	const struct timespec * timeout);
int	__sigwaitinfo(const sigset_t *set, siginfo_t *info);
int	_sigwaitinfo(const sigset_t *set, siginfo_t *info);
int	__sigwait(const sigset_t *set, int *sig);
int	_sigwait(const sigset_t *set, int *sig);
int	__sigsuspend(const sigset_t *sigmask);


static void
sigcancel_handler(int sig __unused,
	siginfo_t *info __unused, ucontext_t *ucp __unused)
{
	struct pthread *curthread = _get_curthread();

	curthread->in_sigcancel_handler++;
	_thr_ast(curthread);
	curthread->in_sigcancel_handler--;
}

void
_thr_ast(struct pthread *curthread)
{

	if (THR_IN_CRITICAL(curthread))
		return;

	if (curthread->cancel_pending && curthread->cancel_enable
		&& !curthread->cancelling) {
		if (curthread->cancel_async) {
			/*
		 	 * asynchronous cancellation mode, act upon
			 * immediately.
		 	 */
			_pthread_exit(PTHREAD_CANCELED);
		} else {
			/*
		 	 * Otherwise, we are in defer mode, and we are at
			 * cancel point, tell kernel to not block the current
			 * thread on next cancelable system call.
			 * 
			 * There are two cases we should call thr_wake() to 
			 * turn on TDP_WAKEUP in kernel:
			 * 1) we are going to call a cancelable system call,
			 *    non-zero cancel_point means we are already in
			 *    cancelable state, next system call is cancelable.
			 * 2) because _thr_ast() may be called by
			 *    THR_CRITICAL_LEAVE() which is used by rtld rwlock
			 *    and any libthr internal locks, when rtld rwlock
			 *    is used, it is mostly caused my an unresolved PLT.
			 *    those routines may clear the TDP_WAKEUP flag by
			 *    invoking some system calls, in those cases, we
			 *    also should reenable the flag.
		 	 */
			if (curthread->cancel_point) {
				if (curthread->cancel_defer)
					thr_wake(curthread->tid);
				else
					_pthread_exit(PTHREAD_CANCELED);
			}
		}
	}

	if (__predict_false((curthread->flags &
	    (THR_FLAGS_NEED_SUSPEND | THR_FLAGS_SUSPENDED))
		== THR_FLAGS_NEED_SUSPEND))
		_thr_suspend_check(curthread);
}

void
_thr_suspend_check(struct pthread *curthread)
{
	uint32_t cycle;
	int err;

	if (curthread->force_exit)
		return;

	err = errno;
	/* 
	 * Blocks SIGCANCEL which other threads must send.
	 */
	_thr_signal_block(curthread);

	/*
	 * Increase critical_count, here we don't use THR_LOCK/UNLOCK
	 * because we are leaf code, we don't want to recursively call
	 * ourself.
	 */
	curthread->critical_count++;
	THR_UMUTEX_LOCK(curthread, &(curthread)->lock);
	while ((curthread->flags & (THR_FLAGS_NEED_SUSPEND |
		THR_FLAGS_SUSPENDED)) == THR_FLAGS_NEED_SUSPEND) {
		curthread->cycle++;
		cycle = curthread->cycle;

		/* Wake the thread suspending us. */
		_thr_umtx_wake(&curthread->cycle, INT_MAX, 0);

		/*
		 * if we are from pthread_exit, we don't want to
		 * suspend, just go and die.
		 */
		if (curthread->state == PS_DEAD)
			break;
		curthread->flags |= THR_FLAGS_SUSPENDED;
		THR_UMUTEX_UNLOCK(curthread, &(curthread)->lock);
		_thr_umtx_wait_uint(&curthread->cycle, cycle, NULL, 0);
		THR_UMUTEX_LOCK(curthread, &(curthread)->lock);
		curthread->flags &= ~THR_FLAGS_SUSPENDED;
	}
	THR_UMUTEX_UNLOCK(curthread, &(curthread)->lock);
	curthread->critical_count--;

	/* 
	 * Unblocks SIGCANCEL, it is possible a new SIGCANCEL is ready and
	 * a new signal frame will nest us, this seems a problem because 
	 * stack will grow and overflow, but because kernel will automatically
	 * mask the SIGCANCEL when delivering the signal, so we at most only
	 * have one nesting signal frame, this should be fine.
	 */
	_thr_signal_unblock(curthread);
	errno = err;
}

void
_thr_signal_init(void)
{
	struct sigaction act;

	/* Install cancel handler. */
	SIGEMPTYSET(act.sa_mask);
	act.sa_flags = SA_SIGINFO | SA_RESTART;
	act.sa_sigaction = (__siginfohandler_t *)&sigcancel_handler;
	__sys_sigaction(SIGCANCEL, &act, NULL);
}

void
_thr_signal_deinit(void)
{
}

__weak_reference(___pause, pause);

int
___pause(void)
{
	struct pthread *curthread = _get_curthread();
	int	ret;

	_thr_cancel_enter(curthread);
	ret = __pause();
	_thr_cancel_leave(curthread);
	
	return ret;
}

__weak_reference(_raise, raise);

int
_raise(int sig)
{
	int ret;

	if (!_thr_isthreaded())
		ret = kill(getpid(), sig);
	else
		ret = _thr_send_sig(_get_curthread(), sig);
	return (ret);
}

__weak_reference(_sigaction, sigaction);

int
_sigaction(int sig, const struct sigaction * act, struct sigaction * oact)
{
	/* Check if the signal number is out of range: */
	if (!_SIG_VALID(sig) || sig == SIGCANCEL) {
		/* Return an invalid argument: */
		errno = EINVAL;
		return (-1);
	}

	return __sys_sigaction(sig, act, oact);
}

__weak_reference(_sigprocmask, sigprocmask);

int
_sigprocmask(int how, const sigset_t *set, sigset_t *oset)
{
	const sigset_t *p = set;
	sigset_t newset;

	if (how != SIG_UNBLOCK) {
		if (set != NULL) {
			newset = *set;
			SIGDELSET(newset, SIGCANCEL);
			p = &newset;
		}
	}
	return (__sys_sigprocmask(how, p, oset));
}

__weak_reference(_pthread_sigmask, pthread_sigmask);

int
_pthread_sigmask(int how, const sigset_t *set, sigset_t *oset)
{
	if (_sigprocmask(how, set, oset))
		return (errno);
	return (0);
}

__weak_reference(__sigsuspend, sigsuspend);

static const sigset_t *
thr_remove_thr_signals(const sigset_t *set, sigset_t *newset)
{
	const sigset_t *pset;

	if (SIGISMEMBER(*set, SIGCANCEL)) {
		*newset = *set;
		SIGDELSET(*newset, SIGCANCEL);
		pset = newset;
	} else
		pset = set;
	return (pset);
}

int
_sigsuspend(const sigset_t * set)
{
	sigset_t newset;

	return (__sys_sigsuspend(thr_remove_thr_signals(set, &newset)));
}

int
__sigsuspend(const sigset_t * set)
{
	struct pthread *curthread = _get_curthread();
	sigset_t newset;
	int ret;

	_thr_cancel_enter(curthread);
	ret = __sys_sigsuspend(thr_remove_thr_signals(set, &newset));
	_thr_cancel_leave(curthread);

	return (ret);
}

__weak_reference(__sigwait, sigwait);
__weak_reference(__sigtimedwait, sigtimedwait);
__weak_reference(__sigwaitinfo, sigwaitinfo);

int
_sigtimedwait(const sigset_t *set, siginfo_t *info,
	const struct timespec * timeout)
{
	sigset_t newset;

	return (__sys_sigtimedwait(thr_remove_thr_signals(set, &newset), info,
	    timeout));
}

/*
 * Cancellation behavior:
 *   Thread may be canceled at start, if thread got signal,
 *   it is not canceled.
 */
int
__sigtimedwait(const sigset_t *set, siginfo_t *info,
	const struct timespec * timeout)
{
	struct pthread	*curthread = _get_curthread();
	sigset_t newset;
	int ret;

	_thr_cancel_enter_defer(curthread, 1);
	ret = __sys_sigtimedwait(thr_remove_thr_signals(set, &newset), info,
	    timeout);
	_thr_cancel_leave_defer(curthread, (ret == -1));
	return (ret);
}

int
_sigwaitinfo(const sigset_t *set, siginfo_t *info)
{
	sigset_t newset;

	return (__sys_sigwaitinfo(thr_remove_thr_signals(set, &newset), info));
}

/*
 * Cancellation behavior:
 *   Thread may be canceled at start, if thread got signal,
 *   it is not canceled.
 */ 
int
__sigwaitinfo(const sigset_t *set, siginfo_t *info)
{
	struct pthread	*curthread = _get_curthread();
	sigset_t newset;
	int ret;

	_thr_cancel_enter_defer(curthread, 1);
	ret = __sys_sigwaitinfo(thr_remove_thr_signals(set, &newset), info);
	_thr_cancel_leave_defer(curthread, ret == -1);
	return (ret);
}

int
_sigwait(const sigset_t *set, int *sig)
{
	sigset_t newset;

	return (__sys_sigwait(thr_remove_thr_signals(set, &newset), sig));
}

/*
 * Cancellation behavior:
 *   Thread may be canceled at start, if thread got signal,
 *   it is not canceled.
 */ 
int
__sigwait(const sigset_t *set, int *sig)
{
	struct pthread	*curthread = _get_curthread();
	sigset_t newset;
	int ret;

	_thr_cancel_enter_defer(curthread, 1);
	ret = __sys_sigwait(thr_remove_thr_signals(set, &newset), sig);
	_thr_cancel_leave_defer(curthread, (ret != 0));
	return (ret);
}