/**
 * \file
 * Stop the world functionality
 *
 * Author:
 * 	Paolo Molaro (lupus@ximian.com)
 *  Rodrigo Kumpera (kumpera@gmail.com)
 *
 * Copyright 2005-2011 Novell, Inc (http://www.novell.com)
 * Copyright 2011 Xamarin Inc (http://www.xamarin.com)
 * Copyright 2011 Xamarin, Inc.
 * Copyright (C) 2012 Xamarin Inc
 *
 * Licensed under the MIT license. See LICENSE file in the project root for full license information.
 */

#include "config.h"
#ifdef HAVE_SGEN_GC

#include "sgen/sgen-gc.h"
#include "sgen/sgen-protocol.h"
#include "sgen/sgen-memory-governor.h"
#include "sgen/sgen-workers.h"
#include "metadata/profiler-private.h"
#include "sgen/sgen-client.h"
#include "metadata/sgen-bridge-internals.h"
#include "metadata/gc-internals.h"
#include "utils/mono-threads.h"
#include "utils/mono-threads-debug.h"

#define TV_DECLARE SGEN_TV_DECLARE
#define TV_GETTIME SGEN_TV_GETTIME
#define TV_ELAPSED SGEN_TV_ELAPSED

static void sgen_unified_suspend_restart_world (void);
static void sgen_unified_suspend_stop_world (void);

static TV_DECLARE (end_of_last_stw);

guint64 mono_time_since_last_stw ()
{
	if (end_of_last_stw == 0)
		return 0;

	TV_DECLARE (current_time);
	TV_GETTIME (current_time);
	return TV_ELAPSED (end_of_last_stw, current_time);
}

unsigned int sgen_global_stop_count = 0;

inline static void*
align_pointer (void *ptr)
{
	mword p = (mword)ptr;
	p += sizeof (gpointer) - 1;
	p &= ~ (sizeof (gpointer) - 1);
	return (void*)p;
}

static void
update_current_thread_stack (void *start)
{
	int stack_guard = 0;
	SgenThreadInfo *info = mono_thread_info_current ();

	info->client_info.stack_start = align_pointer (&stack_guard);
	g_assert (info->client_info.stack_start);
	g_assert (info->client_info.stack_start >= info->client_info.info.stack_start_limit && info->client_info.stack_start < info->client_info.info.stack_end);

#if !defined(MONO_CROSS_COMPILE) && MONO_ARCH_HAS_MONO_CONTEXT
	MONO_CONTEXT_GET_CURRENT (info->client_info.ctx);
#elif defined (HOST_WASM)
	//nothing
#else
	g_error ("Sgen STW requires a working mono-context");
#endif

	if (mono_gc_get_gc_callbacks ()->thread_suspend_func)
		mono_gc_get_gc_callbacks ()->thread_suspend_func (info->client_info.runtime_data, NULL, &info->client_info.ctx);
}

static void
acquire_gc_locks (void)
{
	LOCK_INTERRUPTION;
	mono_thread_info_suspend_lock ();
}

static void
release_gc_locks (void)
{
	mono_thread_info_suspend_unlock ();
	UNLOCK_INTERRUPTION;
}

static TV_DECLARE (stop_world_time);
static unsigned long max_pause_usec = 0;

static guint64 time_stop_world;
static guint64 time_restart_world;

/* LOCKING: assumes the GC lock is held */
void
sgen_client_stop_world (int generation, gboolean serial_collection)
{
	TV_DECLARE (end_handshake);

	MONO_PROFILER_RAISE (gc_event, (MONO_GC_EVENT_PRE_STOP_WORLD, generation, serial_collection));

	acquire_gc_locks ();

	MONO_PROFILER_RAISE (gc_event, (MONO_GC_EVENT_PRE_STOP_WORLD_LOCKED, generation, serial_collection));

	/* We start to scan after locks are taking, this ensures we won't be interrupted. */
	sgen_process_togglerefs ();

	update_current_thread_stack (&generation);

	sgen_global_stop_count++;
	SGEN_LOG (3, "stopping world n %d from %p %p", sgen_global_stop_count, mono_thread_info_current (), (gpointer) (gsize) mono_native_thread_id_get ());
	TV_GETTIME (stop_world_time);

	sgen_unified_suspend_stop_world ();

	SGEN_LOG (3, "world stopped");

	MONO_PROFILER_RAISE (gc_event, (MONO_GC_EVENT_POST_STOP_WORLD, generation, serial_collection));

	TV_GETTIME (end_handshake);
	time_stop_world += TV_ELAPSED (stop_world_time, end_handshake);

	sgen_memgov_collection_start (generation);
	if (sgen_need_bridge_processing ())
		sgen_bridge_reset_data ();
}

/* LOCKING: assumes the GC lock is held */
void
sgen_client_restart_world (int generation, gboolean serial_collection, gint64 *stw_time)
{
	TV_DECLARE (end_sw);
	TV_DECLARE (start_handshake);
	unsigned long usec;

	/* notify the profiler of the leftovers */
	/* FIXME this is the wrong spot at we can STW for non collection reasons. */
	if (MONO_PROFILER_ENABLED (gc_moves))
		mono_sgen_gc_event_moves ();

	if (MONO_PROFILER_ENABLED (gc_resize))
		mono_sgen_gc_event_resize ();

	MONO_PROFILER_RAISE (gc_event, (MONO_GC_EVENT_PRE_START_WORLD, generation, serial_collection));

	FOREACH_THREAD_ALL (info) {
		info->client_info.stack_start = NULL;
		memset (&info->client_info.ctx, 0, sizeof (MonoContext));
	} FOREACH_THREAD_END

	TV_GETTIME (start_handshake);

	sgen_unified_suspend_restart_world ();

	TV_GETTIME (end_sw);
	time_restart_world += TV_ELAPSED (start_handshake, end_sw);
	usec = TV_ELAPSED (stop_world_time, end_sw);
	max_pause_usec = MAX (usec, max_pause_usec);
	end_of_last_stw = end_sw;

	SGEN_LOG (2, "restarted (pause time: %d usec, max: %d)", (int)usec, (int)max_pause_usec);

	MONO_PROFILER_RAISE (gc_event, (MONO_GC_EVENT_POST_START_WORLD, generation, serial_collection));

	/*
	 * We must release the thread info suspend lock after doing
	 * the thread handshake.  Otherwise, if the GC stops the world
	 * and a thread is in the process of starting up, but has not
	 * yet registered (it's not in the thread_list), it is
	 * possible that the thread does register while the world is
	 * stopped.  When restarting the GC will then try to restart
	 * said thread, but since it never got the suspend signal, it
	 * cannot answer the restart signal, so a deadlock results.
	 */
	release_gc_locks ();

	MONO_PROFILER_RAISE (gc_event, (MONO_GC_EVENT_POST_START_WORLD_UNLOCKED, generation, serial_collection));

	*stw_time = usec;
}

void
mono_sgen_init_stw (void)
{
	mono_counters_register ("World stop", MONO_COUNTER_GC | MONO_COUNTER_ULONG | MONO_COUNTER_TIME, &time_stop_world);
	mono_counters_register ("World restart", MONO_COUNTER_GC | MONO_COUNTER_ULONG | MONO_COUNTER_TIME, &time_restart_world);
}

/* Unified suspend code */

static gboolean
sgen_is_thread_in_current_stw (SgenThreadInfo *info, int *reason)
{
	/*
	 * No need to check MONO_THREAD_INFO_FLAGS_NO_GC here as we rely on the
	 * FOREACH_THREAD_EXCLUDE macro to skip such threads for us.
	 */

	/*
	We have detected that this thread is failing/dying, ignore it.
	FIXME: can't we merge this with thread_is_dying?
	*/
	if (info->client_info.skip) {
		if (reason)
			*reason = 2;
		return FALSE;
	}

	/*
	Suspending the current thread will deadlock us, bad idea.
	*/
	if (info == mono_thread_info_current ()) {
		if (reason)
			*reason = 3;
		return FALSE;
	}

	/*
	We can't suspend the workers that will do all the heavy lifting.
	FIXME Use some state bit in SgenThreadInfo for this.
	*/
	if (sgen_thread_pool_is_thread_pool_thread (mono_thread_info_get_tid (info))) {
		if (reason)
			*reason = 4;
		return FALSE;
	}

	/*
	The thread has signaled that it started to detach, ignore it.
	FIXME: can't we merge this with skip
	*/
	if (!mono_thread_info_is_live (info)) {
		if (reason)
			*reason = 5;
		return FALSE;
	}

	return TRUE;
}

static void
sgen_unified_suspend_stop_world (void)
{
	int sleep_duration = -1;

	mono_threads_begin_global_suspend ();
	THREADS_STW_DEBUG ("[GC-STW-BEGIN][%p] *** BEGIN SUSPEND *** \n", mono_thread_info_get_tid (mono_thread_info_current ()));

	for (MonoThreadSuspendPhase phase = MONO_THREAD_SUSPEND_PHASE_INITIAL; phase < MONO_THREAD_SUSPEND_PHASE_COUNT; phase++) {
		gboolean need_next_phase = FALSE;
		FOREACH_THREAD_EXCLUDE (info, MONO_THREAD_INFO_FLAGS_NO_GC) {
			/* look at every thread in the first phase. */
			if (phase == MONO_THREAD_SUSPEND_PHASE_INITIAL) {
				info->client_info.skip = FALSE;
				info->client_info.suspend_done = FALSE;
			} else {
				/* skip threads suspended by previous phase. */
				/* threads with info->client_info->skip set to TRUE will be skipped by sgen_is_thread_in_current_stw. */
				if (info->client_info.suspend_done)
					continue;
			}

			int reason;
			if (!sgen_is_thread_in_current_stw (info, &reason)) {
				THREADS_STW_DEBUG ("[GC-STW-BEGIN-SUSPEND-%d] IGNORE thread %p skip %s reason %d\n", (int)phase, mono_thread_info_get_tid (info), info->client_info.skip ? "true" : "false", reason);
				continue;
			}

			switch (mono_thread_info_begin_suspend (info, phase)) {
			case MONO_THREAD_BEGIN_SUSPEND_SUSPENDED:
				info->client_info.skip = FALSE;
				break;
			case MONO_THREAD_BEGIN_SUSPEND_SKIP:
				info->client_info.skip = TRUE;
				break;
			case MONO_THREAD_BEGIN_SUSPEND_NEXT_PHASE:
				need_next_phase = TRUE;
				break;
			default:
				g_assert_not_reached ();
			}

			THREADS_STW_DEBUG ("[GC-STW-BEGIN-SUSPEND-%d] SUSPEND thread %p skip %s\n", (int)phase, mono_thread_info_get_tid (info), info->client_info.skip ? "true" : "false");
		} FOREACH_THREAD_END;

		mono_thread_info_current ()->client_info.suspend_done = TRUE;
		mono_threads_wait_pending_operations ();

		if (!need_next_phase)
			break;
	}

	for (;;) {
		gint restart_counter = 0;

		FOREACH_THREAD_EXCLUDE (info, MONO_THREAD_INFO_FLAGS_NO_GC) {
			gint suspend_count;

			int reason = 0;
			if (info->client_info.suspend_done || !sgen_is_thread_in_current_stw (info, &reason)) {
				THREADS_STW_DEBUG ("[GC-STW-RESTART] IGNORE RESUME thread %p not been processed done %d current %d reason %d\n", mono_thread_info_get_tid (info), info->client_info.suspend_done, !sgen_is_thread_in_current_stw (info, NULL), reason);
				continue;
			}

			/*
			All threads that reach here are pristine suspended. This means the following:

			- We haven't accepted the previous suspend as good.
			- We haven't gave up on it for this STW (it's either bad or asked not to)
			*/
			if (!mono_thread_info_in_critical_location (info)) {
				info->client_info.suspend_done = TRUE;

				THREADS_STW_DEBUG ("[GC-STW-RESTART] DONE thread %p deemed fully suspended\n", mono_thread_info_get_tid (info));
				continue;
			}

			suspend_count = mono_thread_info_suspend_count (info);
			if (!(suspend_count == 1))
				g_error ("[%p] suspend_count = %d, but should be 1", mono_thread_info_get_tid (info), suspend_count);

			info->client_info.skip = !mono_thread_info_begin_resume (info);
			if (!info->client_info.skip)
				restart_counter += 1;

			THREADS_STW_DEBUG ("[GC-STW-RESTART] RESTART thread %p skip %s\n", mono_thread_info_get_tid (info), info->client_info.skip ? "true" : "false");
		} FOREACH_THREAD_END

		mono_threads_wait_pending_operations ();

		if (restart_counter == 0)
			break;

		if (sleep_duration < 0) {
			mono_thread_info_yield ();
			sleep_duration = 0;
		} else {
			g_usleep (sleep_duration);
			sleep_duration += 10;
		}

		FOREACH_THREAD_EXCLUDE (info, MONO_THREAD_INFO_FLAGS_NO_GC) {
			int reason = 0;
			if (info->client_info.suspend_done || !sgen_is_thread_in_current_stw (info, &reason)) {
				THREADS_STW_DEBUG ("[GC-STW-RESTART] IGNORE SUSPEND thread %p not been processed done %d current %d reason %d\n", mono_thread_info_get_tid (info), info->client_info.suspend_done, !sgen_is_thread_in_current_stw (info, NULL), reason);
				continue;
			}

			if (!mono_thread_info_is_running (info)) {
				THREADS_STW_DEBUG ("[GC-STW-RESTART] IGNORE SUSPEND thread %p not running\n", mono_thread_info_get_tid (info));
				continue;
			}

			switch (mono_thread_info_begin_suspend (info, MONO_THREAD_SUSPEND_PHASE_MOPUP)) {
			case MONO_THREAD_BEGIN_SUSPEND_SUSPENDED:
				info->client_info.skip = FALSE;
				break;
			case MONO_THREAD_BEGIN_SUSPEND_SKIP:
				info->client_info.skip = TRUE;
				break;
			case MONO_THREAD_BEGIN_SUSPEND_NEXT_PHASE:
				g_assert_not_reached ();
			default:
				g_assert_not_reached ();
			}

			THREADS_STW_DEBUG ("[GC-STW-RESTART] SUSPEND thread %p skip %s\n", mono_thread_info_get_tid (info), info->client_info.skip ? "true" : "false");
		} FOREACH_THREAD_END

		mono_threads_wait_pending_operations ();
	}

	FOREACH_THREAD_EXCLUDE (info, MONO_THREAD_INFO_FLAGS_NO_GC) {
		gpointer stopped_ip;

		int reason = 0;
		if (!sgen_is_thread_in_current_stw (info, &reason)) {
			g_assert (!info->client_info.suspend_done || info == mono_thread_info_current ());

			THREADS_STW_DEBUG ("[GC-STW-SUSPEND-END] thread %p is NOT suspended, reason %d\n", mono_thread_info_get_tid (info), reason);
			continue;
		}

		g_assert (info->client_info.suspend_done);

		info->client_info.ctx = mono_thread_info_get_suspend_state (info)->ctx;

		/* Once we remove the old suspend code, we should move sgen to directly access the state in MonoThread */
		info->client_info.stack_start = (gpointer) ((char*)MONO_CONTEXT_GET_SP (&info->client_info.ctx) - REDZONE_SIZE);

		if (info->client_info.stack_start < info->client_info.info.stack_start_limit
			 || info->client_info.stack_start >= info->client_info.info.stack_end) {
			/*
			 * Thread context is in unhandled state, most likely because it is
			 * dying. We don't scan it.
			 * FIXME We should probably rework and check the valid flag instead.
			 */
			info->client_info.stack_start = NULL;
		}

		stopped_ip = (gpointer) (MONO_CONTEXT_GET_IP (&info->client_info.ctx));

		sgen_binary_protocol_thread_suspend ((gpointer) mono_thread_info_get_tid (info), stopped_ip);

		THREADS_STW_DEBUG ("[GC-STW-SUSPEND-END] thread %p is suspended, stopped_ip = %p, stack = %p -> %p\n",
			mono_thread_info_get_tid (info), stopped_ip, info->client_info.stack_start, info->client_info.stack_start ? info->client_info.info.stack_end : NULL);
	} FOREACH_THREAD_END
}

static void
sgen_unified_suspend_restart_world (void)
{
	THREADS_STW_DEBUG ("[GC-STW-END] *** BEGIN RESUME ***\n");
	FOREACH_THREAD_EXCLUDE (info, MONO_THREAD_INFO_FLAGS_NO_GC) {
		int reason = 0;
		if (sgen_is_thread_in_current_stw (info, &reason)) {
			g_assert (mono_thread_info_begin_resume (info));
			THREADS_STW_DEBUG ("[GC-STW-RESUME-WORLD] RESUME thread %p\n", mono_thread_info_get_tid (info));

			sgen_binary_protocol_thread_restart ((gpointer) mono_thread_info_get_tid (info));
		} else {
			THREADS_STW_DEBUG ("[GC-STW-RESUME-WORLD] IGNORE thread %p, reason %d\n", mono_thread_info_get_tid (info), reason);
		}
	} FOREACH_THREAD_END

	mono_threads_wait_pending_operations ();
	mono_threads_end_global_suspend ();
}
#endif
