| 1 | /* |
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| 2 | * queuelock.h: local kernel lock with waiting queue implementation. |
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| 3 | * |
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| 4 | * Authors Alain Greiner (2016,2017,2018) |
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| 5 | * |
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| 6 | * Copyright (c) UPMC Sorbonne Universites |
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| 7 | * |
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| 8 | * This file is part of ALMOS-MKH. |
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| 9 | * |
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| 10 | * ALMOS-MKH is free software; you can redistribute it and/or modify it |
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| 11 | * under the terms of the GNU General Public License as published by |
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| 12 | * the Free Software Foundation; version 2.0 of the License. |
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| 13 | * |
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| 14 | * ALMOS-MKH is distributed in the hope that it will be useful, but |
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| 15 | * WITHOUT ANY WARRANTY; without even the implied warranty of |
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| 16 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
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| 17 | * General Public License for more details. |
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| 18 | * |
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| 19 | * You should have received a copy of the GNU General Public License |
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| 20 | * along with ALMOS-kernel; if not, write to the Free Software Foundation, |
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| 21 | * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA |
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| 22 | */ |
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| 23 | |
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| 24 | #ifndef _QUEUELOCK_H_ |
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| 25 | #define _QUEUELOCK_H_ |
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| 26 | |
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| 27 | #include <kernel_config.h> |
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| 28 | #include <hal_kernel_types.h> |
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| 29 | #include <busylock.h> |
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| 30 | #include <list.h> |
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| 31 | |
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| 32 | /******************************************************************************************* |
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| 33 | * This synchronisation object sequencializes concurrent read or write accesses to a |
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| 34 | * locally shared object in a given cluster (i.e. made by thread(s) running in same cluster. |
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| 35 | * This lock has only two states: taken or free. |
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| 36 | * When the lock has been taken by another thread T', the thread T executing the |
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| 37 | * queuelock_acquire() function blocks and deschedules, after registering in the waiting |
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| 38 | * queue rooted in lock descriptor. The first thread in the waiting queue will be unblocked |
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| 39 | * by the owner thread executing the queuelock_release() function. |
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| 40 | * To handle concurrent accesses between a thread T executing the acquire() function |
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| 41 | * and a thread T' executing the release() function, the "queuelock" is protected |
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| 42 | * by a "busylock" used by these two access functions. |
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| 43 | * WARNING: this queuelock is NOT registered in the thread "local_locks" field. |
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| 44 | ******************************************************************************************/ |
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| 45 | |
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| 46 | |
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| 47 | /******************************************************************************************* |
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| 48 | * This structure defines a queuelock. |
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| 49 | ******************************************************************************************/ |
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| 50 | |
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| 51 | typedef struct queuelock_s |
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| 52 | { |
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| 53 | busylock_t lock; /*! protect atomic access to queuelock */ |
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| 54 | volatile uint32_t taken; /*! state : free if zero / taken if non zero */ |
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| 55 | list_entry_t root; /*! root of list of locally waiting threads */ |
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| 56 | } |
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| 57 | queuelock_t; |
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| 58 | |
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| 59 | /******************************************************************************************* |
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| 60 | * This function initializes a local queuelock in free state. |
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| 61 | * The <type> argument defines the lock usage and is only used for debug. |
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| 62 | * This type is actually stored in the associated busylock descriptor. |
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| 63 | ******************************************************************************************* |
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| 64 | * @ lock : local pointer on queuelock. |
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| 65 | * @ type : lock usage for debug. |
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| 66 | ******************************************************************************************/ |
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| 67 | inline void queuelock_init( queuelock_t * lock, |
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| 68 | uint32_t type ); |
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| 69 | |
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| 70 | /******************************************************************************************* |
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| 71 | * This blocking function acquires a queuelock. |
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| 72 | * The calling thread and the lock must be in same cluster. |
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| 73 | * It uses the busylock to atomically access/update the queuelock state. |
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| 74 | * If the lock is already taken, the calling thread atomically registers in the list |
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| 75 | * of waiting threads (rooted in the lock descriptor), block and deschedule. |
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| 76 | ******************************************************************************************* |
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| 77 | * @ lock : local pointer on queuelock. |
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| 78 | ******************************************************************************************/ |
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| 79 | void queuelock_acquire( queuelock_t * lock ); |
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| 80 | |
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| 81 | /******************************************************************************************* |
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| 82 | * This function releases a queuelock. |
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| 83 | * The calling thread and the lock must be in same cluster. |
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| 84 | * It uses the busylock to atomically access/update the queuelock state. |
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| 85 | * If the list of waiting threads is not empty, the first waiting thread is unblocked. |
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| 86 | ******************************************************************************************* |
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| 87 | * @ lock : local pointer on queuelock. |
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| 88 | ******************************************************************************************/ |
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| 89 | void queuelock_release( queuelock_t * lock ); |
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| 90 | |
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| 91 | |
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| 92 | #endif /* _QUEUELOCK_H_ */ |
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