1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
|
/*****************************************************************************
* sched/sched_waitpid.c
*
* Copyright (C) 2011-2012 Gregory Nutt. All rights reserved.
* Author: Gregory Nutt <gnutt@nuttx.org>
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
* 3. Neither the name NuttX nor the names of its contributors may be
* used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*
*****************************************************************************/
/*****************************************************************************
* Included Files
*****************************************************************************/
#include <nuttx/config.h>
#include <sys/wait.h>
#include <semaphore.h>
#include <errno.h>
#include <nuttx/sched.h>
#include "os_internal.h"
#ifdef CONFIG_SCHED_WAITPID /* Experimental */
/*****************************************************************************
* Private Functions
*****************************************************************************/
/*****************************************************************************
* Public Functions
*****************************************************************************/
/*****************************************************************************
* Name: sched_waitpid
*
* Description:
*
* The waitpid() functions will obtain status information pertaining to one
* of the caller's child processes. The waitpid() function will suspend
* execution of the calling thread until status information for one of the
* terminated child processes of the calling process is available, or until
* delivery of a signal whose action is either to execute a signal-catching
* function or to terminate the process. If more than one thread is suspended
* in waitpid() awaiting termination of the same process, exactly one thread
* will return the process status at the time of the target process
* termination. If status information is available prior to the call to
* waitpid(), return will be immediate.
*
* The pid argument specifies a set of child processes for which status is
* requested. The waitpid() function will only return the status of a child
* process from this set:
*
* - If pid is equal to (pid_t)-1, status is requested for any child process.
* In this respect, waitpid() is then equivalent to wait().
* - If pid is greater than 0, it specifies the process ID of a single child
* process for which status is requested.
* - If pid is 0, status is requested for any child process whose process
* group ID is equal to that of the calling process.
* - If pid is less than (pid_t)-1, status is requested for any child process
* whose process group ID is equal to the absolute value of pid.
*
* The options argument is constructed from the bitwise-inclusive OR of zero
* or more of the following flags, defined in the <sys/wait.h> header:
*
* WCONTINUED - The waitpid() function will report the status of any
* continued child process specified by pid whose status has not been
* reported since it continued from a job control stop.
* WNOHANG - The waitpid() function will not suspend execution of the
* calling thread if status is not immediately available for one of the
* child processes specified by pid.
* WUNTRACED - The status of any child processes specified by pid that are
* stopped, and whose status has not yet been reported since they stopped,
* will also be reported to the requesting process.
*
* If the calling process has SA_NOCLDWAIT set or has SIGCHLD set to
* SIG_IGN, and the process has no unwaited-for children that were
* transformed into zombie processes, the calling thread will block until all
* of the children of the process containing the calling thread terminate, and
* waitpid() will fail and set errno to ECHILD.
*
* If waitpid() returns because the status of a child process is available,
* these functions will return a value equal to the process ID of the child
* process. In this case, if the value of the argument stat_loc is not a
* null pointer, information will be stored in the location pointed to by
* stat_loc. The value stored at the location pointed to by stat_loc will be
* 0 if and only if the status returned is from a terminated child process
* that terminated by one of the following means:
*
* 1. The process returned 0 from main().
* 2. The process called _exit() or exit() with a status argument of 0.
* 3. The process was terminated because the last thread in the process terminated.
*
* Regardless of its value, this information may be interpreted using the
* following macros, which are defined in <sys/wait.h> and evaluate to
* integral expressions; the stat_val argument is the integer value pointed
* to by stat_loc.
*
* WIFEXITED(stat_val) - Evaluates to a non-zero value if status was
* returned for a child process that terminated normally.
* WEXITSTATUS(stat_val) - If the value of WIFEXITED(stat_val) is non-zero,
* this macro evaluates to the low-order 8 bits of the status argument
* that the child process passed to _exit() or exit(), or the value the
* child process returned from main().
* WIFSIGNALED(stat_val) - Evaluates to a non-zero value if status was
* returned for a child process that terminated due to the receipt of a
* signal that was not caught (see <signal.h>).
* WTERMSIG(stat_val) - If the value of WIFSIGNALED(stat_val) is non-zero,
* this macro evaluates to the number of the signal that caused the
* termination of the child process.
* WIFSTOPPED(stat_val) - Evaluates to a non-zero value if status was
* returned for a child process that is currently stopped.
* WSTOPSIG(stat_val) - If the value of WIFSTOPPED(stat_val) is non-zero,
* this macro evaluates to the number of the signal that caused the child
* process to stop.
* WIFCONTINUED(stat_val) - Evaluates to a non-zero value if status was
* returned for a child process that has continued from a job control stop.
*
* Parameters:
* pid - The task ID of the thread to waid for
* stat_loc - The location to return the exit status
* options - ignored
*
* Return Value:
* If waitpid() returns because the status of a child process is available,
* it will return a value equal to the process ID of the child process for
* which status is reported.
*
* If waitpid() returns due to the delivery of a signal to the calling
* process, -1 will be returned and errno set to EINTR.
*
* If waitpid() was invoked with WNOHANG set in options, it has at least
* one child process specified by pid for which status is not available, and
* status is not available for any process specified by pid, 0 is returned.
*
* Otherwise, (pid_t)-1 will be returned, and errno set to indicate the error:
*
* ECHILD - The process specified by pid does not exist or is not a child of
* the calling process, or the process group specified by pid does not exist
* or does not have any member process that is a child of the calling process.
* EINTR - The function was interrupted by a signal. The value of the location
* pointed to by stat_loc is undefined.
* EINVAL - The options argument is not valid.
*
* Assumptions:
*
*****************************************************************************/
/***************************************************************************/
/* NOTE: This is a partially functional, experimental version of waitpid() */
/***************************************************************************/
pid_t waitpid(pid_t pid, int *stat_loc, int options)
{
_TCB *tcb;
bool mystat;
int err;
int ret;
/* Disable pre-emption so that nothing changes in the following tests */
sched_lock();
tcb = sched_gettcb(pid);
if (!tcb)
{
err = ECHILD;
goto errout_with_errno;
}
/* None of the options are supported */
#ifdef CONFIG_DEBUG
if (options != 0)
{
err = ENOSYS;
goto errout_with_errno;
}
#endif
/* "If more than one thread is suspended in waitpid() awaiting termination of
* the same process, exactly one thread will return the process status at the
* time of the target process termination." Hmmm.. what do we return to the
* others?
*/
if (stat_loc != NULL && tcb->stat_loc == NULL)
{
tcb->stat_loc = stat_loc;
mystat = true;
}
/* Then wait for the task to exit */
ret = sem_wait(&tcb->exitsem);
if (ret < 0)
{
/* Unlock pre-emption and return the ERROR (sem_wait has already set
* the errno). Handle the awkward case of whether or not we need to
* nullify the stat_loc value.
*/
if (mystat)
{
tcb->stat_loc = NULL;
}
goto errout;
}
/* On success, return the PID */
sched_unlock();
return pid;
errout_with_errno:
set_errno(err);
errout:
sched_unlock();
return ERROR;
}
#endif /* CONFIG_SCHED_WAITPID */
|
