| [1] | 1 | /* |
|---|
| 2 | * remote_rwlock.h - kernel remote_rwlock definition. |
|---|
| 3 | * |
|---|
| 4 | * Authors Alain Greiner (2016) |
|---|
| 5 | * |
|---|
| 6 | * Copyright (c) UPMC Sorbonne Universites |
|---|
| 7 | * |
|---|
| 8 | * This file is part of ALMOS-MKH. |
|---|
| 9 | * |
|---|
| 10 | * ALMOS-MKH is free software; you can redistribute it and/or modify it |
|---|
| 11 | * under the terms of the GNU General Public License as published by |
|---|
| 12 | * the Free Software Foundation; version 2.0 of the License. |
|---|
| 13 | * |
|---|
| 14 | * ALMOS-MKH is distributed in the hope that it will be useful, but |
|---|
| 15 | * WITHOUT ANY WARRANTY; without even the implied warranty of |
|---|
| 16 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
|---|
| 17 | * General Public License for more details. |
|---|
| 18 | * |
|---|
| 19 | * You should have received a copy of the GNU General Public License |
|---|
| 20 | * along with ALMOS-MKH; if not, write to the Free Software Foundation, |
|---|
| 21 | * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA |
|---|
| 22 | */ |
|---|
| 23 | |
|---|
| 24 | #ifndef _REMOTE_RWLOCK_H_ |
|---|
| 25 | #define _REMOTE_RWLOCK_H_ |
|---|
| 26 | |
|---|
| 27 | #include <almos_config.h> |
|---|
| 28 | #include <hal_types.h> |
|---|
| 29 | #include <xlist.h> |
|---|
| 30 | |
|---|
| 31 | /*************************************************************************************** |
|---|
| 32 | * This structure defines a remote rwdlock,that supports several simultaneous read |
|---|
| 33 | * accesses, but only one write access. It implements a ticket based allocation policy. |
|---|
| 34 | * It can be used to synchronize threads running in different clusters, because |
|---|
| 35 | * all access functions use remote pointers. |
|---|
| 36 | * - A reader take the lock to atomically increments the registered readers count. |
|---|
| 37 | * Then it release the lock and access the protected structure. It atomically |
|---|
| 38 | * decrements the readers count without taking the lock when access is completed. |
|---|
| 39 | * - A writer take the lock and keep it, but must wait completion of all current read |
|---|
| 40 | * accesses before starting its own access. |
|---|
| 41 | * When the lock is taken by another thread, the new-comers use a busy waiting policy. |
|---|
| 42 | * |
|---|
| 43 | * TODO This could be replaced by a descheduling policy and a threads waiting queue |
|---|
| 44 | * implemented in the lock itself: each thread releasing the lock (i.e. incrementing |
|---|
| 45 | * the current field) activates the first waiting thread... |
|---|
| 46 | **************************************************************************************/ |
|---|
| 47 | |
|---|
| 48 | typedef struct remote_rwlock_s |
|---|
| 49 | { |
|---|
| 50 | uint32_t ticket; /*! first free ticket index */ |
|---|
| 51 | uint32_t current; /*! ticket index of current owner */ |
|---|
| 52 | uint32_t count; /*! current number of reader threads */ |
|---|
| 53 | xptr_t owner; /*! extended pointer on writer thread */ |
|---|
| 54 | } |
|---|
| 55 | remote_rwlock_t; |
|---|
| 56 | |
|---|
| 57 | /*************************************************************************************** |
|---|
| 58 | * This function initializes a remote rwlock. |
|---|
| 59 | *************************************************************************************** |
|---|
| 60 | * @ lock_xp : extended pointer on the remote rwlock |
|---|
| 61 | **************************************************************************************/ |
|---|
| 62 | void remote_rwlock_init( xptr_t lock_xp ); |
|---|
| 63 | |
|---|
| 64 | /*************************************************************************************** |
|---|
| 65 | * This blocking function get access to a remote rwlock for a reader. |
|---|
| 66 | * It increments the calling thread locks count when the lock has been taken. |
|---|
| 67 | *************************************************************************************** |
|---|
| 68 | * @ lock_xp : extended pointer on the remote rwlock |
|---|
| 69 | **************************************************************************************/ |
|---|
| 70 | void remote_rwlock_rd_lock( xptr_t lock_xp ); |
|---|
| 71 | |
|---|
| 72 | /*************************************************************************************** |
|---|
| 73 | * This function releases a remote rwlock for a reader. |
|---|
| 74 | * It decrements the calling thread locks count when the lock has been released. |
|---|
| 75 | *************************************************************************************** |
|---|
| 76 | * @ lock_xp : extended pointer on the remote rwlock |
|---|
| 77 | **************************************************************************************/ |
|---|
| 78 | void remote_rwlock_rd_unlock( xptr_t lock_xp ); |
|---|
| 79 | |
|---|
| 80 | /*************************************************************************************** |
|---|
| 81 | * This blocking function get access to a remote rwlock for a writer. |
|---|
| 82 | * It increments the calling thread locks count when the lock has been taken. |
|---|
| 83 | *************************************************************************************** |
|---|
| 84 | * @ lock_xp : extended pointer on the remote rwlock |
|---|
| 85 | **************************************************************************************/ |
|---|
| 86 | void remote_rwlock_wr_lock( xptr_t lock_xp ); |
|---|
| 87 | |
|---|
| 88 | /*************************************************************************************** |
|---|
| 89 | * This function releases a remote rwlock for a writer. |
|---|
| 90 | * It decrements the calling thread locks count when the lock has been released. |
|---|
| 91 | *************************************************************************************** |
|---|
| 92 | * @ lock_xp : extended pointer on the remote rwlock |
|---|
| 93 | **************************************************************************************/ |
|---|
| 94 | void remote_rwlock_wr_unlock( xptr_t lock_xp ); |
|---|
| 95 | |
|---|
| 96 | #endif |
|---|
