source: trunk/kernel/libk/remote_barrier.h @ 23

Last change on this file since 23 was 23, checked in by alain, 8 years ago

Introduce syscalls.
File size: 7.0 KB
Line 
1/*
2 * remote_barrier.h - Access a POSIX barrier.               
3 *
4 * Author  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_BARRIER_H_
25#define _REMOTE_BARRIER_H_
26
27#include <kernel_config.h>
28#include <hal_types.h>
29#include <remote_spinlock.h>
30#include <xlist.h>
31
32/***************************************************************************************
33 *          This file defines a POSIX compliant barrier.
34 *
35 * It is used by multi-threaded applications to synchronise threads running in
36 * different clusters, as all access functions uses hal_remote_lw() / hal_remote_sw()
37 * portable remote access primitives.
38 *
39 * A barrier is declared by a given user process as a "pthread_barrier_t" global variable.
40 * This user type is implemented as an unsigned long, but the value is not used by the
41 * kernel. ALMOS-MKH uses only the barrier virtual address as an identifier.
42 * For each user barrier, ALMOS-MKH creates a kernel "remote_barrier_t" structure,
43 * dynamically allocated in the reference cluster by the remote_barrier_create() function,
44 * and destroyed by the remote_barrier_destroy() function, using RPC if the calling thread
45 * is not running in the reference cluster.
46 *
47 * The blocking "remote_barrier_wait()" function implements a descheduling policy when
48 * the calling thread is not the last expected thread: the calling thread is registered
49 * in a waiting queue, rooted in the barrier structure, and the the calling thread
50 * is blocked on the THREAD_BLOCKED_USERSYNC condition. The last arrived thread
51 * unblocks all registtered waiting threads.
52 *
53 * Implementation note:
54 * This barrier is also used by the kernel in the parallel kernel_init phase, as the
55 * remote_barrier() function does not require barrier initialisation, when the barrier
56 * is statically allocated by the compiler in the kdata segment.
57 * **************************************************************************************/
58
59/*****************************************************************************************
60 * This structure defines the barrier descriptor.
61 * - It contains an xlist of all barriers dynamically created by a given process,
62 *   rooted in the reference process descriptor.
63 * - It contains the root of another xlist to register all arrived threads.
64 ****************************************************************************************/
65
66typedef struct remote_barrier_s
67{
68    remote_spinlock_t  lock;          /*! lock protecting list of arrived threads       */
69    intptr_t           ident;         /*! virtual address in user space == identifier   */
70    uint32_t           current;       /*! number of arrived threads                     */
71    uint32_t           sense;         /*! barrier state (toggle)                        */
72    uint32_t           nb_threads;    /*! number of expected threads                    */ 
73    xlist_entry_t      list;          /*! member of list of barriers in same process    */
74    xlist_entry_t      root;          /*! root of list of arrived threads               */
75} 
76remote_barrier_t;
77
78/*****************************************************************************************
79 * This function is directly used by the kernel in the kernel_init phase,
80 * because it does not require barrier state initialisation.
81 * It returns only when the <count> expected threads reach the barrier.
82 *****************************************************************************************
83 * @ barrier_xp  : extended pointer on barrier descriptor.
84 * @ count       : number of expected threads.
85 ****************************************************************************************/
86inline void remote_barrier( xptr_t   barrier_xp, 
87                            uint32_t count );
88
89
90/*****************************************************************************************
91 * This function returns an extended pointer on the remote barrier identified
92 * by its virtual address in a given user process. It makes an associative search,
93 * scanning the list of barriers rooted in the reference process descriptor.
94 *****************************************************************************************
95 * @ ident    : barrier virtual address, used as identifier.
96 * @ returns extended pointer on barrier if success / returns XPTR_NULL if not found.
97 ****************************************************************************************/
98xptr_t remote_barrier_from_ident( intptr_t  ident );
99
100/*****************************************************************************************
101 * This function implement the pthread_barrier_init() syscall.
102 * It allocates memory for the barrier descriptor in the reference cluster for
103 * the calling process, it initializes the barrier state, and register it in the
104 * list of barriers owned by the reference process.
105 *****************************************************************************************
106 * @ count       : number of expected threads.
107 * @ ident       : barrier identifier (virtual address in user space).
108 * @ return 0 if success / return ENOMEM if failure.
109 ****************************************************************************************/
110error_t remote_barrier_create( intptr_t ident,
111                               uint32_t count );
112
113/*****************************************************************************************
114 * This function implement the pthread_barrier_destroy() syscall.
115 * It releases thr memory allocated for the barrier descriptor, and remove the barrier
116 * from the list of barriers owned by the reference process.
117 *****************************************************************************************
118 * @ barrier_xp  : extended pointer on barrier descriptor.
119 ****************************************************************************************/
120void remote_barrier_destroy( xptr_t   barrier_xp );
121
122/*****************************************************************************************
123 * This function implement the pthread_barrier_wait() syscall.
124 * It returns only when the number of expected threads (registered in the barrier
125 * dexcriptor) reach the barrier.
126 *****************************************************************************************
127 * @ barrier_xp   : extended pointer on barrier descriptor.
128 ****************************************************************************************/
129void remote_barrier_wait( xptr_t   barrier_xp );
130
131
132#endif  /* _REMOTE_BARRIER_H_ */
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