source: trunk/kernel/syscalls/sys_fork.c @ 435

Last change on this file since 435 was 435, checked in by alain, 4 years ago

Fix a bad bug in scheduler...

File size: 6.1 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_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
48    pid_t             child_pid;            // child process identifier
49    thread_t        * child_thread_ptr;     // local pointer on remote child thread descriptor
50    cxy_t             target_cxy;           // target cluster for forked child process
51 
52    xptr_t            ref_process_xp;       // extended pointer on reference parent process
53    cxy_t             ref_process_cxy;      // cluster of reference parent process
54    process_t       * ref_process_ptr;      // local pointer on reference parent process
55
56        error_t           error;
57   
58
59    // get pointers on local parent process and thread
60        parent_thread_ptr  = CURRENT_THREAD;
61    parent_thread_xp   = XPTR( local_cxy , parent_thread_ptr );
62        parent_process_ptr = parent_thread_ptr->process;
63    parent_pid         = parent_process_ptr->pid;
64
65#if CONFIG_DEBUG_SYS_FORK
66uint64_t          tm_start;
67uint64_t          tm_end;
68tm_start = hal_get_cycles();
69if( CONFIG_DEBUG_SYS_FORK < tm_start )
70printk("\n[DBG] %s : thread %x enter / parent %x / cycle =  %d\n",
71__FUNCTION__, parent_thread_ptr, parent_pid, (uint32_t)tm_start );
72#endif
73
74    // get infos on reference process
75    ref_process_xp  = parent_process_ptr->ref_xp;
76    ref_process_cxy = GET_CXY( ref_process_xp );
77    ref_process_ptr = (process_t *)GET_PTR( ref_process_xp );
78
79    // check parent process children number from reference
80    xptr_t   children_xp = XPTR( ref_process_cxy , &ref_process_ptr->children_nr );
81    if( hal_remote_atomic_add( children_xp , 1 ) >= CONFIG_PROCESS_MAX_CHILDREN )
82        {
83
84#if CONFIG_DEBUG_SYSCALLS_ERROR
85printk("\n[ERROR] in %s : too much children processes\n", __FUNCTION__);
86#endif
87            hal_remote_atomic_add ( children_xp , -1 );
88        parent_thread_ptr->errno = EAGAIN;
89        return -1;
90        }
91
92    // Select target cluster for child process and main thread.
93    // If placement is not user-defined, the placement is defined by the DQDT.
94        if( parent_thread_ptr->fork_user )    // user defined placement
95        {
96        target_cxy = parent_thread_ptr->fork_cxy;
97        parent_thread_ptr->fork_user = false;
98        }
99        else                                  // DQDT placement
100        {
101                target_cxy = dqdt_get_cluster_for_process();
102        }
103
104    // call process_make_fork in target cluster
105    if( target_cxy == local_cxy )
106    {
107        error = process_make_fork( ref_process_xp,
108                                   parent_thread_xp,
109                                   &child_pid,
110                                   &child_thread_ptr );
111    }
112    else
113    {
114        rpc_process_make_fork_client( target_cxy,
115                                      ref_process_xp,
116                                      parent_thread_xp,
117                                      &child_pid,
118                                      &child_thread_ptr,
119                                      &error );
120    }
121
122    if( error )
123    {
124
125#if CONFIG_DEBUG_SYSCALLS_ERROR
126printk("\n[ERROR] in %s : cannot fork process %x in cluster %x\n",
127__FUNCTION__, parent_pid, local_cxy );
128#endif
129        parent_thread_ptr->errno = EAGAIN;
130        return -1;
131    }
132
133    // set remote child FPU_context from parent_thread register values
134    // only when the parent thread is the FPU owner
135        if( CURRENT_THREAD->core->fpu_owner == parent_thread_ptr )
136        {
137                hal_fpu_context_save( XPTR( target_cxy , child_thread_ptr ) );
138        }
139
140    // set remote child CPU context from  parent_thread register values
141    hal_cpu_context_fork( XPTR( target_cxy , child_thread_ptr ) );
142
143    // From this point, both parent and child threads execute the following code.
144    // They can be distinguished by the CURRENT_THREAD value, and child will only
145    // execute it when it is unblocked by parent.
146    // - parent unblock child, and return child PID to user application.
147    // - child thread does nothing, and return 0 to user pplication
148
149    thread_t * current = CURRENT_THREAD;
150
151    if( current == parent_thread_ptr )    // current == parent thread
152    {
153        // parent_thread unblock child_thread
154        thread_unblock( XPTR( target_cxy , child_thread_ptr ) , THREAD_BLOCKED_GLOBAL );
155
156#if CONFIG_DEBUG_SYS_FORK
157tm_end = hal_get_cycles();
158if( CONFIG_DEBUG_SYS_FORK < tm_end )
159printk("\n[DBG] %s : parent_thread %x exit / cost = %d / cycle %d\n",
160__FUNCTION__ , parent_thread_ptr, (uint32_t)(tm_end - tm_start), (uint32_t)tm_end );
161#endif
162
163        return child_pid;
164    }
165        else                                   // current == child_thread
166    {
167
168#if CONFIG_DEBUG_SYS_FORK
169tm_end = hal_get_cycles();
170if( CONFIG_DEBUG_SYS_FORK < tm_end )
171printk("\n[DBG] %s : child_thread %x exit / cost = %d / cycle %d\n",
172__FUNCTION__ , child_thread_ptr, (uint32_t)(tm_end - tm_start), (uint32_t)tm_end );
173#endif
174
175        return 0;
176    }
177
178}  // end sys_fork()
179
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