//
// Cforall Version 1.0.0 Copyright (C) 2016 University of Waterloo
//
// The contents of this file are covered under the licence agreement in the
// file "LICENCE" distributed with Cforall.
//
// bits/locks.h -- Fast internal locks.
//
// Author           : Thierry Delisle
// Created On       : Tue Oct 31 15:14:38 2017
// Last Modified By : Peter A. Buhr
// Last Modified On : Fri Mar 30 18:18:13 2018
// Update Count     : 9
//

#pragma once

#include "bits/debug.h"
#include "bits/defs.h"
#include <assert.h>

#ifdef __cforall
	extern "C" {
		#include <pthread.h>
	}
#endif

// pause to prevent excess processor bus usage
#if defined( __sparc )
	#define Pause() __asm__ __volatile__ ( "rd %ccr,%g0" )
#elif defined( __i386 ) || defined( __x86_64 )
	#define Pause() __asm__ __volatile__ ( "pause" : : : )
#elif defined( __ARM_ARCH )
	#define Pause() __asm__ __volatile__ ( "nop" : : : )
#else
	#error unsupported architecture
#endif

#if defined( __i386 ) || defined( __x86_64 ) || defined( __ARM_ARCH )
	// Intel recommendation
	#define __ALIGN__ __attribute__(( aligned (128) ))
#elif defined( __sparc )
	#define __ALIGN__ CALIGN
#else
	#error unsupported architecture
#endif

struct __spinlock_t {
	// Wrap in struct to prevent false sharing with debug info
	struct {
		// Align lock on 128-bit boundary
		__ALIGN__ volatile _Bool lock;
	};
	#ifdef __CFA_DEBUG__
		// previous function to acquire the lock
		const char * prev_name;
		// previous thread to acquire the lock
		void* prev_thrd;
	#endif
} __ALIGN__;

#ifdef __cforall
	extern "C" {
		extern void disable_interrupts();
		extern void enable_interrupts_noPoll();
	}

	extern void yield( unsigned int );

	static inline void ?{}( __spinlock_t & this ) {
		this.lock = 0;
	}


	#ifdef __CFA_DEBUG__
		void __cfaabi_dbg_record(__spinlock_t & this, const char * prev_name);
	#else
		#define __cfaabi_dbg_record(x, y)
	#endif

	// Lock the spinlock, return false if already acquired
	static inline _Bool try_lock  ( __spinlock_t & this __cfaabi_dbg_ctx_param2 ) {
		_Bool result = (this.lock == 0) && (__atomic_test_and_set( &this.lock, __ATOMIC_ACQUIRE ) == 0);
		if( result ) {
			disable_interrupts();
			__cfaabi_dbg_record( this, caller );
		}
		return result;
	}

	// Lock the spinlock, spin if already acquired
	static inline void lock( __spinlock_t & this __cfaabi_dbg_ctx_param2 ) {
		#ifndef NOEXPBACK
			enum { SPIN_START = 4, SPIN_END = 64 * 1024, };
			unsigned int spin = SPIN_START;
		#endif

		for ( unsigned int i = 1;; i += 1 ) {
			if ( (this.lock == 0) && (__atomic_test_and_set( &this.lock, __ATOMIC_ACQUIRE ) == 0) ) break;
			#ifndef NOEXPBACK
				// exponential spin
				for ( volatile unsigned int s = 0; s < spin; s += 1 ) Pause();

				// slowly increase by powers of 2
				if ( i % 64 == 0 ) spin += spin;

				// prevent overflow
				if ( spin > SPIN_END ) spin = SPIN_START;
			#else
				Pause();
			#endif
		}
		disable_interrupts();
		__cfaabi_dbg_record( this, caller );
	}

	static inline void unlock( __spinlock_t & this ) {
		enable_interrupts_noPoll();
		__atomic_clear( &this.lock, __ATOMIC_RELEASE );
	}


	#ifdef __CFA_WITH_VERIFY__
		extern bool __cfaabi_dbg_in_kernel();
	#endif

	struct __bin_sem_t {
		int_fast8_t     counter;
		pthread_mutex_t lock;
		pthread_cond_t  cond;
	};

	static inline void ?{}(__bin_sem_t & this) with( this ) {
		counter = 0;
		pthread_mutex_init(&lock, NULL);
		pthread_cond_init (&cond, NULL);
	}

	static inline void ^?{}(__bin_sem_t & this) with( this ) {
		pthread_mutex_destroy(&lock);
		pthread_cond_destroy (&cond);
	}

	static inline void wait(__bin_sem_t & this) with( this ) {
		verify(__cfaabi_dbg_in_kernel());
		pthread_mutex_lock(&lock);
		if(counter != 0) {   // this must be a loop, not if!
			pthread_cond_wait(&cond, &lock);
		}
		counter = 1;
		pthread_mutex_unlock(&lock);
	}

	static inline void post(__bin_sem_t & this) with( this ) {
		verify(__cfaabi_dbg_in_kernel());
		pthread_mutex_lock(&lock);
		bool needs_signal = counter == 0;
		counter = 1;
		pthread_mutex_unlock(&lock);
		if (!needs_signal)
			pthread_cond_signal(&cond);
		}
#endif