source: trunk/kernel/syscalls/sys_fork.c @ 459

Last change on this file since 459 was 457, checked in by alain, 3 years ago

This version modifies the exec syscall and fixes a large number of small bugs.
The version number has been updated (0.1)

File size: 6.4 KB
Line 
1/*
2 * sys_fork.c - Kernel function implementing the "fork" system call.
3 *
4 * Authors  Alain Greiner  (2016,2017)
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//////////////
41int sys_fork()
42{
43        process_t       * parent_process_ptr;   // pointer on local parent process descriptor
44    xptr_t            parent_thread_xp;     // extended pointer on parent thread descriptor
45    pid_t             parent_pid;           // parent process identifier
46    thread_t        * parent_thread_ptr;    // local pointer on local parent thread descriptor
47    cxy_t             parent_cxy;           // parent thread cluster
48
49    pid_t             child_pid;            // child process identifier
50    thread_t        * child_thread_ptr;     // local pointer on remote child thread descriptor
51    cxy_t             child_cxy;            // target cluster for forked child process
52 
53    xptr_t            ref_process_xp;       // extended pointer on reference parent process
54    cxy_t             ref_process_cxy;      // cluster of reference parent process
55    process_t       * ref_process_ptr;      // local pointer on reference parent process
56
57        error_t           error;
58   
59
60    // get pointers on local parent process and thread
61        parent_thread_ptr  = CURRENT_THREAD;
62    parent_thread_xp   = XPTR( local_cxy , parent_thread_ptr );
63        parent_process_ptr = parent_thread_ptr->process;
64    parent_pid         = parent_process_ptr->pid;
65    parent_cxy         = local_cxy;
66
67#if DEBUG_SYS_FORK
68uint64_t          tm_start;
69uint64_t          tm_end;
70tm_start = hal_get_cycles();
71if( DEBUG_SYS_FORK < tm_start )
72printk("\n[DBG] %s : thread %x in process %x enter / cycle =  %d\n",
73__FUNCTION__, parent_thread_ptr->trdid, parent_pid, (uint32_t)tm_start );
74#endif
75
76    // get infos on reference parent process
77    ref_process_xp  = parent_process_ptr->ref_xp;
78    ref_process_cxy = GET_CXY( ref_process_xp );
79    ref_process_ptr = GET_PTR( ref_process_xp );
80
81    // check parent process children number from reference
82    xptr_t   children_xp = XPTR( ref_process_cxy , &ref_process_ptr->children_nr );
83    if( hal_remote_atomic_add( children_xp , 1 ) >= CONFIG_PROCESS_MAX_CHILDREN )
84        {
85
86#if DEBUG_SYSCALLS_ERROR
87printk("\n[ERROR] in %s : too much children processes\n", __FUNCTION__);
88#endif
89            hal_remote_atomic_add ( children_xp , -1 );
90        parent_thread_ptr->errno = EAGAIN;
91        return -1;
92        }
93
94    // Select target cluster for child process and main thread.
95    // If placement is not user-defined, it is defined by the DQDT.
96        if( parent_thread_ptr->fork_user )
97        {
98        child_cxy = parent_thread_ptr->fork_cxy;
99        parent_thread_ptr->fork_user = false;
100        }
101        else                                  // DQDT placement
102        {
103                child_cxy = dqdt_get_cluster_for_process();
104        }
105
106#if (DEBUG_SYS_FORK & 1 )
107if( DEBUG_SYS_FORK < tm_start )
108printk("\n[DBG] %s : thread %x in process %x selected cluster %x\n",
109__FUNCTION__, parent_thread_ptr->trdid, parent_pid, child_cxy );
110#endif
111
112    // call process_make_fork in target cluster
113    if( child_cxy == local_cxy )
114    {
115        error = process_make_fork( ref_process_xp,
116                                   parent_thread_xp,
117                                   &child_pid,
118                                   &child_thread_ptr );
119    }
120    else
121    {
122        rpc_process_make_fork_client( child_cxy,
123                                      ref_process_xp,
124                                      parent_thread_xp,
125                                      &child_pid,
126                                      &child_thread_ptr,
127                                      &error );
128    }
129
130    if( error )
131    {
132
133#if DEBUG_SYSCALLS_ERROR
134printk("\n[ERROR] in %s : cannot fork process %x in cluster %x\n",
135__FUNCTION__, parent_pid, local_cxy );
136#endif
137        parent_thread_ptr->errno = EAGAIN;
138        return -1;
139    }
140
141    // set remote child FPU_context from parent_thread register values
142    // only when the parent thread is the FPU owner
143        if( CURRENT_THREAD->core->fpu_owner == parent_thread_ptr )
144        {
145                hal_fpu_context_save( XPTR( child_cxy , child_thread_ptr ) );
146        }
147
148    // set remote child CPU context from parent_thread register values
149    hal_cpu_context_fork( XPTR( child_cxy , child_thread_ptr ) );
150
151    // From this point, both parent and child threads execute the following code,
152    // but they can be distinguished by the (CURRENT_THREAD,local_cxy) values.
153    // - parent unblock child, and return child PID to user application.
154    // - child thread does nothing, and return 0 to user pplication
155    // The child thread will only execute it when it is unblocked by parent thread.
156
157    thread_t * current = CURRENT_THREAD;
158
159    if( (current == parent_thread_ptr) && (local_cxy == parent_cxy) )   // parent thread
160    {
161        // parent_thread unblock child_thread
162        thread_unblock( XPTR( child_cxy , child_thread_ptr ) , THREAD_BLOCKED_GLOBAL );
163
164#if DEBUG_SYS_FORK
165tm_end = hal_get_cycles();
166if( DEBUG_SYS_FORK < tm_end )
167printk("\n[DBG] %s : process %x exit / cost = %d / cycle %d\n",
168__FUNCTION__, parent_pid, (uint32_t)(tm_end - tm_start), (uint32_t)tm_end );
169#endif
170        return child_pid;
171    }
172        else                                                               // child_thread
173    {
174
175#if DEBUG_SYS_FORK
176tm_end = hal_get_cycles();
177if( DEBUG_SYS_FORK < tm_end )
178printk("\n[DBG] %s : process %x exit / cost = %d / cycle %d\n",
179__FUNCTION__, child_pid, (uint32_t)(tm_end - tm_start), (uint32_t)tm_end );
180#endif
181        return 0;
182    }
183
184}  // end sys_fork()
185
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