/*
 * spinlock.h: kernel spinlock definition     
 * 
 * Authors  Alain Greiner (2016,2017,2018)
 *
 * Copyright (c) UPMC Sorbonne Universites
 *
 * This file is part of ALMOS-MKH.
 *
 * ALMOS-MKH is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License as published by
 * the Free Software Foundation; version 2.0 of the License.
 *
 * ALMOS-MKH is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with ALMOS-kernel; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
 */

#ifndef _SPINLOCK_H_
#define _SPINLOCK_H_

#include <kernel_config.h>
#include <hal_kernel_types.h>
#include <list.h>

/*******************************************************************************************
 * This structure defines a local spinlock, that sequencializes all read or write accesses
 * in a given cluster. A new access can only start after completion of the previous access, 
 * when the owner thread releases the lock. The lock has only two states: taken or free.
 * The owner thread is registered in the spinlock_t structure, and the calling thread
 * list of local spinlocks is updated. 
 * 
 * A spinlock can be accessed in three modes :
 *
 * - The spinlock_lock() function is BLOCKING and use a descheduling policy when the lock
 *   is already taken. The lock must be released with the spinlock_unlock() function.
 * - The spinlock_lock_noirq() function is BLOCKING, but uses a polling (busy-waiting)
 *   policy if the lock is already taken. The IRQs can be disabled or not depending
 *   on the irq_state argument. The lock must be released with the spinlock_unlock_noirq()
 *   function.
 * - The spinlock_trylock() function is NON-BLOCKING, and tries only once to take the lock.
 *   It must be released with the spinlock_unlock() function.
 ******************************************************************************************/

/****     Forward declarations    ****/

struct thread_s;

/*******************************************************************************************
 * This structure defines a local spinlock.
 * The "owner" and "list" are optionnal fields used for debug. 
 * It register the list of all spinlocks taken by a given thread.
 ******************************************************************************************/

typedef struct spinlock_s
{
	uint32_t            taken;             /*! state : free if zero / taken if non zero  */

#if DEBUG_SPINLOCKS
	struct thread_s   * owner;             /*! pointer on curent owner thread            */
    list_entry_t        list;              /*! member of list of locks taken by owner    */
#endif

}
spinlock_t;

/*******************************************************************************************
 * This function initializes a local spinlock in free state.
 *******************************************************************************************
 * @ lock    : pointer on spinlock.
 ******************************************************************************************/
inline void spinlock_init( spinlock_t * lock );

/*******************************************************************************************
 * This blocking function uses a busy waiting strategy to lock a local spinlock.
 * It polls the lock and returns only when the lock has been taken.
 * All IRQs are disabled and will keep disabled until the lock is released. 
 * It increments the calling thread local_locks count when the lock has been taken.
 *******************************************************************************************
 * @ lock       : pointer on spinlock
 * @ irq_state  : buffer to save the SR state (in the calling thread stack)
 ******************************************************************************************/
void spinlock_lock_busy( spinlock_t * lock,
                         uint32_t   * irq_state );

/*******************************************************************************************
 * This function releases a local busy_waiting spinlock.
 * It restores the CPU SR state.
 *******************************************************************************************
 * @ lock       : pointer on spinlock
 * @ irq_state  : value to be resrored in CPU SR 
 ******************************************************************************************/
void spinlock_unlock_busy( spinlock_t * lock,
                           uint32_t     irq_state );

/*******************************************************************************************
 * This blocking function locks a local spinlock.
 * If the lock is already taken, the calling thread deschedules without blocking,
 * and retries when it is rescheduled, until success.
 * It increments the calling thread local_locks count when the lock has been taken.
 *******************************************************************************************
 * @ lock       : pointer on spinlock
 ******************************************************************************************/
void spinlock_lock( spinlock_t * lock );

/*******************************************************************************************
 * This non-blocking function tries once to lock a spinlock.
 * It increments the calling thread locks count in case of success.
 *******************************************************************************************
 * @ lock       : pointer on spinlock
 * @ returns 0 if success / returns non zero if lock already taken. 
 ******************************************************************************************/
error_t spinlock_trylock( spinlock_t * lock );

/*******************************************************************************************
 * This function releases a spinlock and do schedule if necessary.
 *******************************************************************************************
 * @ lock       : pointer on spinlock
 ******************************************************************************************/
void spinlock_unlock( spinlock_t * lock );


#endif	/* _SPINLOCK_H_ */
