source: trunk/kernel/syscalls/sys_fork.c

Last change on this file was 670, checked in by alain, 2 weeks ago

1) Introduce up to 4 command lines arguments in the KSH "load" command.
These arguments are transfered to the user process through the
argc/argv mechanism, using the user space "args" vseg.

2) Introduce the named and anonymous "pipes", for inter-process communication
through the pipe() and mkfifo() syscalls.

3) Introduce the "chat" application to validate the two above mechanisms.

4) Improve printk() and assert() fonctions in printk.c.

File size: 7.3 KB
Line 
1/*
2 * sys_fork.c - Kernel function implementing the "fork" system call.
3 *
4 * Authors  Alain Greiner  (2016,2017,2018,2019,2020)
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#include <kernel_config.h>
25#include <hal_kernel_types.h>
26#include <hal_context.h>
27#include <hal_switch.h>
28#include <hal_atomic.h>
29#include <errno.h>
30#include <printk.h>
31#include <core.h>
32#include <cluster.h>
33#include <list.h>
34#include <thread.h>
35#include <scheduler.h>
36#include <kmem.h>
37#include <dqdt.h>
38#include <process.h>
39
40#include <syscalls.h>
41
42////////////////////
43int sys_fork( void )
44{
45        process_t       * parent_process_ptr;   // pointer on local parent process descriptor
46    xptr_t            parent_thread_xp;     // extended pointer on parent thread descriptor
47    pid_t             parent_pid;           // parent process identifier
48    thread_t        * parent_thread_ptr;    // local pointer on local parent thread
49    cxy_t             parent_cxy;           // parent thread cluster
50
51    pid_t             child_pid;            // child process identifier
52    thread_t        * child_thread_ptr;     // local pointer on remote child thread
53    cxy_t             child_cxy;            // target cluster for forked child process
54 
55    xptr_t            ref_process_xp;       // extended pointer on reference parent process
56    cxy_t             ref_process_cxy;      // cluster of reference parent process
57    process_t       * ref_process_ptr;      // local pointer on reference parent process
58
59        error_t           error;
60
61    // get pointers on local parent process and thread
62        parent_thread_ptr  = CURRENT_THREAD;
63    parent_thread_xp   = XPTR( local_cxy , parent_thread_ptr );
64        parent_process_ptr = parent_thread_ptr->process;
65    parent_pid         = parent_process_ptr->pid;
66    parent_cxy         = local_cxy;
67
68#if DEBUG_SYS_FORK || DEBUG_SYSCALLS_ERROR || CONFIG_INSTRUMENTATION_SYSCALLS
69uint64_t     tm_start = hal_get_cycles();
70#endif
71
72#if DEBUG_SYS_FORK
73if( DEBUG_SYS_FORK < (uint32_t)tm_start )
74printk("\n[%s] thread[%x,%x] enter / cycle =  %d\n",
75__FUNCTION__, parent_pid, parent_thread_ptr->trdid, (uint32_t)tm_start );
76#endif
77
78    // get infos on reference parent process
79    ref_process_xp  = parent_process_ptr->ref_xp;
80    ref_process_cxy = GET_CXY( ref_process_xp );
81    ref_process_ptr = GET_PTR( ref_process_xp );
82
83    // check parent process children number from reference
84    xptr_t   children_xp = XPTR( ref_process_cxy , &ref_process_ptr->children_nr );
85    if( hal_remote_atomic_add( children_xp , 1 ) >= CONFIG_PROCESS_MAX_CHILDREN )
86        {
87
88#if DEBUG_SYSCALLS_ERROR
89if( DEBUG_SYSCALLS_ERROR < (uint32_t)tm_start )
90printk("\n[ERROR] in %s : thread[%x,%x] / too much children\n",
91__FUNCTION__, parent_pid, parent_thread_ptr->trdid );
92#endif
93            hal_remote_atomic_add ( children_xp , -1 );
94        parent_thread_ptr->errno = EAGAIN;
95        return -1;
96        }
97
98    // Select target cluster for child process and main thread.
99    // If placement is not user-defined, it is defined by the DQDT.
100        if( parent_thread_ptr->fork_user )
101        {
102        child_cxy = parent_thread_ptr->fork_cxy;
103        parent_thread_ptr->fork_user = false;
104        }
105        else                                  // DQDT placement
106        {
107                child_cxy = dqdt_get_cluster_for_thread( LOCAL_CLUSTER->dqdt_root_xp );
108        }
109
110#if (DEBUG_SYS_FORK & 1 )
111if( DEBUG_SYS_FORK < (uint32_t)tm_start )
112printk("\n[%s] thread[%x,%x] selected cluster %x\n",
113__FUNCTION__, parent_pid, parent_thread_ptr->trdid, child_cxy );
114#endif
115
116    // call process_make_fork in target cluster
117    if( child_cxy == local_cxy )
118    {
119        error = process_make_fork( ref_process_xp,
120                                   parent_thread_xp,
121                                   &child_pid,
122                                   &child_thread_ptr );
123    }
124    else
125    {
126        rpc_process_make_fork_client( child_cxy,
127                                      ref_process_xp,
128                                      parent_thread_xp,
129                                      &child_pid,
130                                      &child_thread_ptr,
131                                      &error );
132    }
133
134    if( error )
135    {
136
137#if DEBUG_SYSCALLS_ERROR
138if( DEBUG_SYSCALLS_ERROR < (uint32_t)tm_start )
139printk("\n[ERROR] in %s : thread[%x,%x] cannot fork\n",
140__FUNCTION__, parent_pid, parent_thread_ptr->trdid );
141#endif
142        parent_thread_ptr->errno = EAGAIN;
143        return -1;
144    }
145
146    // set remote child FPU_context from parent_thread register values
147    // only when the parent thread is the FPU owner
148        if( CURRENT_THREAD->core->fpu_owner == parent_thread_ptr )
149        {
150                hal_fpu_context_save( XPTR( child_cxy , child_thread_ptr ) );
151        }
152
153    // set the remote child CPU context from parent register values,
154    // set the remote child uzone from
155    // replicates the parent thread kernel stack to the child thread descriptor,
156    // and finally unblock the child thread.
157    hal_cpu_context_fork( XPTR( child_cxy , child_thread_ptr ) );
158
159    // From this point, both parent and child threads execute the following code,
160    // but child thread will only execute it after being unblocked by parent thread.
161    // They can be distinguished by the (CURRENT_THREAD,local_cxy) values.
162    // - parent return child PID to user application.
163    // - child  return 0 to user application
164
165    thread_t * current = CURRENT_THREAD;
166
167#if (DEBUG_SYS_FORK || CONFIG_INSTRUMENTATION_SYSCALLS)
168uint64_t     tm_end = hal_get_cycles();
169#endif
170
171    if( (current == parent_thread_ptr) && (local_cxy == parent_cxy) )   // parent thread
172    {
173
174#if DEBUG_SYS_FORK
175if( DEBUG_SYS_FORK < (uint32_t)tm_end )
176printk("\n[%s] parent thread[%x,%x] exit / child_pid %x / cycle %d\n",
177__FUNCTION__, current->process->pid, current->trdid, child_pid, (uint32_t)tm_end );
178#endif
179
180// only parent display the parent and child VMM
181#if (DEBUG_SYS_FORK & 1 )
182if( DEBUG_SYS_FORK < (uint32_t)tm_end )
183{
184    process_t * child_process_ptr = hal_remote_lpt( XPTR( child_cxy , 
185                                                          &child_thread_ptr->process ) );
186    xptr_t      child_process_xp  = XPTR( child_cxy , child_process_ptr );
187
188    hal_vmm_display( ref_process_xp , true ); 
189    hal_vmm_display( child_process_xp , true );
190}
191#endif
192
193// only parent contribute to syscalls instrumentation
194#if CONFIG_INSTRUMENTATION_SYSCALLS
195hal_atomic_add( &syscalls_cumul_cost[SYS_FORK] , tm_end - tm_start );
196hal_atomic_add( &syscalls_occurences[SYS_FORK] , 1 );
197#endif
198        return child_pid;
199    }
200        else                                                               // child_thread
201    {
202
203#if DEBUG_SYS_FORK
204if( DEBUG_SYS_FORK < (uint32_t)tm_end )
205printk("\n[%s] child thread[%x,%x] exit / child_pid %x / cycle %d\n",
206__FUNCTION__, current->process->pid, current->trdid, child_pid, (uint32_t)tm_end );
207#endif
208
209        return 0;
210    }
211
212}  // end sys_fork()
213
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