1 | /* |
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2 | * remote_sem.h - POSIX unnamed semaphore definition. |
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3 | * |
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4 | * Author Alain Greiner (2016,2017,2018,2019,2020) |
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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 | e* 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-MKH; 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 _SEMAPHORE_H_ |
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25 | #define _SEMAPHORE_H_ |
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26 | |
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27 | #include <hal_kernel_types.h> |
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28 | #include <xlist.h> |
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29 | #include <remote_busylock.h> |
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30 | |
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31 | /********************************************************************************************n |
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32 | * This is the kernel representation of an user level, POSIX compliant unnamed semaphore. |
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33 | * |
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34 | * It can be used by muti-threaded user applications to synchronise user threads |
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35 | * running in different clusters. |
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36 | * |
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37 | * A semaphore is declared by a given user process as a "sem_t" global variable. |
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38 | * The user "sem_t" structure is implemented as an unsigned long, but the value is not |
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39 | * used by the kernel. ALMOS-MKH uses only the sem_t virtual address as an identifier. |
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40 | * For each user semaphore, ALMOS-MKH creates a kernel "remote_sem_t" structure, |
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41 | * dynamically allocated in the reference cluster by the remote_sem_create() function, |
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42 | * and destroyed by the remote_sem_destroy() function, using RPC if the calling thread is not |
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43 | * running in the reference cluster. |
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44 | * |
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45 | * The threads accessing the semaphore with the sem_get_value(), sem_wait(), sem_post() |
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46 | * syscalls can be running in any cluster, as these syscalls access the "remote_sem_t" |
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47 | * structure with remote_read / remote_write access functions. |
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48 | ********************************************************************************************/ |
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49 | |
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50 | |
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51 | /********************************************************************************************* |
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52 | * This structure defines the kernel implementation of an user level semaphore. |
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53 | ********************************************************************************************/ |
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54 | |
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55 | typedef struct remote_sem_s |
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56 | { |
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57 | remote_busylock_t lock; /*! lock protecting the semaphore state */ |
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58 | uint32_t count; /*! current value */ |
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59 | intptr_t ident; /*! virtual address in user space == identifier */ |
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60 | xlist_entry_t root; /*! root of waiting thread queue */ |
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61 | xlist_entry_t list; /*! member of list of semaphores in same process */ |
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62 | } |
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63 | remote_sem_t; |
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64 | |
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65 | |
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66 | /********************************************************************************************* |
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67 | * This function returns an extended pointer on the remote semaphore identified |
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68 | * by its virtual address in a given user process. It makes an associative search, |
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69 | * scanning the list of user semaphores rooted in the reference process descriptor. |
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70 | ********************************************************************************************* |
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71 | * @ process : pointer on local process descriptor. |
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72 | * @ ident : semaphore virtual address, used as identifier. |
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73 | * @ returns extended pointer on semaphore if success / returns XPTR_NULL if not found. |
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74 | ********************************************************************************************/ |
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75 | xptr_t remote_sem_from_ident( intptr_t ident ); |
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76 | |
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77 | /********************************************************************************************* |
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78 | * This function implements the SEM_INIT operation. |
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79 | * It allocates memory for a remote semaphore in reference cluster, using a RPC if required, |
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80 | * and initializes it, using remote accesses from values defined by the <vaddr> and <value> |
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81 | * arguments. It register this semaphore in the calling process list of user semaphores. |
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82 | ********************************************************************************************* |
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83 | * @ vaddr : [in] semaphore virtual address, used as identifier. |
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84 | * @ value : [in] semaphore initial value. |
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85 | * @ returns 0 if success / returns -1 if no memory. |
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86 | ********************************************************************************************/ |
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87 | error_t remote_sem_create( intptr_t vaddr, |
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88 | uint32_t value ); |
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89 | |
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90 | /****************************yy*************************************************************** |
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91 | * This function implements the SEM_DESTROY operation. |
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92 | * It desactivates the semaphore, and releases the physical memory allocated in the |
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93 | * reference cluster, using a RPC if required. |
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94 | ********************************************************************************************* |
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95 | * @ sem_xp : [in] extended pointer on semaphore. |
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96 | ********************************************************************************************/ |
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97 | void remote_sem_destroy( xptr_t sem_xp ); |
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98 | |
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99 | /****************************yy*************************************************************** |
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100 | * This blocking function implements the SEM_WAIT operation. |
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101 | * - It returns only when the remote semaphore has a non-zero value, and has been |
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102 | * atomically decremented. |
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103 | * - If the semaphore has a zero value, it register the calling thread in the semaphore |
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104 | * waiting queue, block the thread, and yield. |
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105 | ********************************************************************************************* |
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106 | * @ sem_xp : [in] extended pointer on semaphore. |
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107 | ********************************************************************************************/ |
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108 | void remote_sem_wait( xptr_t sem_xp ); |
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109 | |
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110 | /****************************yy*************************************************************** |
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111 | * This function implements the SEM_POST operation. |
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112 | * - It atomically increments the remote semaphore. |
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113 | * - If the waiting queue is not empty, it wakes up all waiting thread. |
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114 | ********************************************************************************************* |
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115 | * @ sem_xp : [in] extended pointer on semaphore. |
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116 | ********************************************************************************************/ |
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117 | void remote_sem_post( xptr_t sem_xp ); |
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118 | |
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119 | /****************************yy*************************************************************** |
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120 | * This function implements the SEM_GETVALUE operation. |
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121 | * It returns in the <data> buffer the semaphore current value. |
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122 | ********************************************************************************************* |
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123 | * @ sem_xp : [in] extended pointer on semaphore. |
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124 | * @ data : [out] local pointer on buffer for returned value. |
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125 | ********************************************************************************************/ |
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126 | void remote_sem_get_value( xptr_t sem_xp, |
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127 | uint32_t * data ); |
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128 | |
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129 | |
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130 | #endif /* _SEMAPHORE_H_ */ |
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