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parallel.c
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1 /*
2  * parallel.c
3  *
4  * multi-process support
5  *
6  * Copyright (c) 2010-2023, PostgreSQL Global Development Group
7  * src/bin/pg_upgrade/parallel.c
8  */
9 
10 #include "postgres_fe.h"
11 
12 #include <sys/wait.h>
13 #ifdef WIN32
14 #include <io.h>
15 #endif
16 
17 #include "pg_upgrade.h"
18 
19 static int parallel_jobs;
20 
21 #ifdef WIN32
22 /*
23  * Array holding all active threads. There can't be any gaps/zeros so
24  * it can be passed to WaitForMultipleObjects(). We use two arrays
25  * so the thread_handles array can be passed to WaitForMultipleObjects().
26  */
27 HANDLE *thread_handles;
28 
29 typedef struct
30 {
31  char *log_file;
32  char *opt_log_file;
33  char *cmd;
34 } exec_thread_arg;
35 
36 typedef struct
37 {
38  DbInfoArr *old_db_arr;
39  DbInfoArr *new_db_arr;
40  char *old_pgdata;
41  char *new_pgdata;
42  char *old_tablespace;
43 } transfer_thread_arg;
44 
45 exec_thread_arg **exec_thread_args;
46 transfer_thread_arg **transfer_thread_args;
47 
48 /* track current thread_args struct so reap_child() can be used for all cases */
49 void **cur_thread_args;
50 
51 DWORD win32_exec_prog(exec_thread_arg *args);
52 DWORD win32_transfer_all_new_dbs(transfer_thread_arg *args);
53 #endif
54 
55 /*
56  * parallel_exec_prog
57  *
58  * This has the same API as exec_prog, except it does parallel execution,
59  * and therefore must throw errors and doesn't return an error status.
60  */
61 void
62 parallel_exec_prog(const char *log_file, const char *opt_log_file,
63  const char *fmt,...)
64 {
65  va_list args;
66  char cmd[MAX_STRING];
67 
68 #ifndef WIN32
69  pid_t child;
70 #else
71  HANDLE child;
72  exec_thread_arg *new_arg;
73 #endif
74 
75  va_start(args, fmt);
76  vsnprintf(cmd, sizeof(cmd), fmt, args);
77  va_end(args);
78 
79  if (user_opts.jobs <= 1)
80  /* exit_on_error must be true to allow jobs */
81  exec_prog(log_file, opt_log_file, true, true, "%s", cmd);
82  else
83  {
84  /* parallel */
85 #ifdef WIN32
86  if (thread_handles == NULL)
87  thread_handles = pg_malloc(user_opts.jobs * sizeof(HANDLE));
88 
89  if (exec_thread_args == NULL)
90  {
91  int i;
92 
93  exec_thread_args = pg_malloc(user_opts.jobs * sizeof(exec_thread_arg *));
94 
95  /*
96  * For safety and performance, we keep the args allocated during
97  * the entire life of the process, and we don't free the args in a
98  * thread different from the one that allocated it.
99  */
100  for (i = 0; i < user_opts.jobs; i++)
101  exec_thread_args[i] = pg_malloc0(sizeof(exec_thread_arg));
102  }
103 
104  cur_thread_args = (void **) exec_thread_args;
105 #endif
106  /* harvest any dead children */
107  while (reap_child(false) == true)
108  ;
109 
110  /* must we wait for a dead child? */
112  reap_child(true);
113 
114  /* set this before we start the job */
115  parallel_jobs++;
116 
117  /* Ensure stdio state is quiesced before forking */
118  fflush(NULL);
119 
120 #ifndef WIN32
121  child = fork();
122  if (child == 0)
123  /* use _exit to skip atexit() functions */
124  _exit(!exec_prog(log_file, opt_log_file, true, true, "%s", cmd));
125  else if (child < 0)
126  /* fork failed */
127  pg_fatal("could not create worker process: %s", strerror(errno));
128 #else
129  /* empty array element are always at the end */
130  new_arg = exec_thread_args[parallel_jobs - 1];
131 
132  /* Can only pass one pointer into the function, so use a struct */
133  pg_free(new_arg->log_file);
134  new_arg->log_file = pg_strdup(log_file);
135  pg_free(new_arg->opt_log_file);
136  new_arg->opt_log_file = opt_log_file ? pg_strdup(opt_log_file) : NULL;
137  pg_free(new_arg->cmd);
138  new_arg->cmd = pg_strdup(cmd);
139 
140  child = (HANDLE) _beginthreadex(NULL, 0, (void *) win32_exec_prog,
141  new_arg, 0, NULL);
142  if (child == 0)
143  pg_fatal("could not create worker thread: %s", strerror(errno));
144 
145  thread_handles[parallel_jobs - 1] = child;
146 #endif
147  }
148 }
149 
150 
151 #ifdef WIN32
152 DWORD
153 win32_exec_prog(exec_thread_arg *args)
154 {
155  int ret;
156 
157  ret = !exec_prog(args->log_file, args->opt_log_file, true, true, "%s", args->cmd);
158 
159  /* terminates thread */
160  return ret;
161 }
162 #endif
163 
164 
165 /*
166  * parallel_transfer_all_new_dbs
167  *
168  * This has the same API as transfer_all_new_dbs, except it does parallel execution
169  * by transferring multiple tablespaces in parallel
170  */
171 void
173  char *old_pgdata, char *new_pgdata,
174  char *old_tablespace)
175 {
176 #ifndef WIN32
177  pid_t child;
178 #else
179  HANDLE child;
180  transfer_thread_arg *new_arg;
181 #endif
182 
183  if (user_opts.jobs <= 1)
184  transfer_all_new_dbs(old_db_arr, new_db_arr, old_pgdata, new_pgdata, NULL);
185  else
186  {
187  /* parallel */
188 #ifdef WIN32
189  if (thread_handles == NULL)
190  thread_handles = pg_malloc(user_opts.jobs * sizeof(HANDLE));
191 
192  if (transfer_thread_args == NULL)
193  {
194  int i;
195 
196  transfer_thread_args = pg_malloc(user_opts.jobs * sizeof(transfer_thread_arg *));
197 
198  /*
199  * For safety and performance, we keep the args allocated during
200  * the entire life of the process, and we don't free the args in a
201  * thread different from the one that allocated it.
202  */
203  for (i = 0; i < user_opts.jobs; i++)
204  transfer_thread_args[i] = pg_malloc0(sizeof(transfer_thread_arg));
205  }
206 
207  cur_thread_args = (void **) transfer_thread_args;
208 #endif
209  /* harvest any dead children */
210  while (reap_child(false) == true)
211  ;
212 
213  /* must we wait for a dead child? */
215  reap_child(true);
216 
217  /* set this before we start the job */
218  parallel_jobs++;
219 
220  /* Ensure stdio state is quiesced before forking */
221  fflush(NULL);
222 
223 #ifndef WIN32
224  child = fork();
225  if (child == 0)
226  {
227  transfer_all_new_dbs(old_db_arr, new_db_arr, old_pgdata, new_pgdata,
228  old_tablespace);
229  /* if we take another exit path, it will be non-zero */
230  /* use _exit to skip atexit() functions */
231  _exit(0);
232  }
233  else if (child < 0)
234  /* fork failed */
235  pg_fatal("could not create worker process: %s", strerror(errno));
236 #else
237  /* empty array element are always at the end */
238  new_arg = transfer_thread_args[parallel_jobs - 1];
239 
240  /* Can only pass one pointer into the function, so use a struct */
241  new_arg->old_db_arr = old_db_arr;
242  new_arg->new_db_arr = new_db_arr;
243  pg_free(new_arg->old_pgdata);
244  new_arg->old_pgdata = pg_strdup(old_pgdata);
245  pg_free(new_arg->new_pgdata);
246  new_arg->new_pgdata = pg_strdup(new_pgdata);
247  pg_free(new_arg->old_tablespace);
248  new_arg->old_tablespace = old_tablespace ? pg_strdup(old_tablespace) : NULL;
249 
250  child = (HANDLE) _beginthreadex(NULL, 0, (void *) win32_transfer_all_new_dbs,
251  new_arg, 0, NULL);
252  if (child == 0)
253  pg_fatal("could not create worker thread: %s", strerror(errno));
254 
255  thread_handles[parallel_jobs - 1] = child;
256 #endif
257  }
258 }
259 
260 
261 #ifdef WIN32
262 DWORD
263 win32_transfer_all_new_dbs(transfer_thread_arg *args)
264 {
265  transfer_all_new_dbs(args->old_db_arr, args->new_db_arr, args->old_pgdata,
266  args->new_pgdata, args->old_tablespace);
267 
268  /* terminates thread */
269  return 0;
270 }
271 #endif
272 
273 
274 /*
275  * collect status from a completed worker child
276  */
277 bool
278 reap_child(bool wait_for_child)
279 {
280 #ifndef WIN32
281  int work_status;
282  pid_t child;
283 #else
284  int thread_num;
285  DWORD res;
286 #endif
287 
288  if (user_opts.jobs <= 1 || parallel_jobs == 0)
289  return false;
290 
291 #ifndef WIN32
292  child = waitpid(-1, &work_status, wait_for_child ? 0 : WNOHANG);
293  if (child == (pid_t) -1)
294  pg_fatal("%s() failed: %s", "waitpid", strerror(errno));
295  if (child == 0)
296  return false; /* no children, or no dead children */
297  if (work_status != 0)
298  pg_fatal("child process exited abnormally: status %d", work_status);
299 #else
300  /* wait for one to finish */
301  thread_num = WaitForMultipleObjects(parallel_jobs, thread_handles,
302  false, wait_for_child ? INFINITE : 0);
303 
304  if (thread_num == WAIT_TIMEOUT || thread_num == WAIT_FAILED)
305  return false;
306 
307  /* compute thread index in active_threads */
308  thread_num -= WAIT_OBJECT_0;
309 
310  /* get the result */
311  GetExitCodeThread(thread_handles[thread_num], &res);
312  if (res != 0)
313  pg_fatal("child worker exited abnormally: %s", strerror(errno));
314 
315  /* dispose of handle to stop leaks */
316  CloseHandle(thread_handles[thread_num]);
317 
318  /* Move last slot into dead child's position */
319  if (thread_num != parallel_jobs - 1)
320  {
321  void *tmp_args;
322 
323  thread_handles[thread_num] = thread_handles[parallel_jobs - 1];
324 
325  /*
326  * Move last active thread arg struct into the now-dead slot, and the
327  * now-dead slot to the end for reuse by the next thread. Though the
328  * thread struct is in use by another thread, we can safely swap the
329  * struct pointers within the array.
330  */
331  tmp_args = cur_thread_args[thread_num];
332  cur_thread_args[thread_num] = cur_thread_args[parallel_jobs - 1];
333  cur_thread_args[parallel_jobs - 1] = tmp_args;
334  }
335 #endif
336 
337  /* do this after job has been removed */
338  parallel_jobs--;
339 
340  return true;
341 }
bool exec_prog(const char *log_filename, const char *opt_log_file, bool report_error, bool exit_on_error, const char *fmt,...)
Definition: exec.c:86
static int parallel_jobs
Definition: parallel.c:19
void parallel_transfer_all_new_dbs(DbInfoArr *old_db_arr, DbInfoArr *new_db_arr, char *old_pgdata, char *new_pgdata, char *old_tablespace)
Definition: parallel.c:172
bool reap_child(bool wait_for_child)
Definition: parallel.c:278
void parallel_exec_prog(const char *log_file, const char *opt_log_file, const char *fmt,...)
Definition: parallel.c:62
void * pg_malloc0(size_t size)
Definition: fe_memutils.c:53
char * pg_strdup(const char *in)
Definition: fe_memutils.c:85
void pg_free(void *ptr)
Definition: fe_memutils.c:105
void * pg_malloc(size_t size)
Definition: fe_memutils.c:47
int i
Definition: isn.c:73
static void const char * fmt
static void const char fflush(stdout)
va_end(args)
va_start(args, fmt)
#define pg_fatal(...)
static char * log_file
Definition: pg_ctl.c:86
void transfer_all_new_dbs(DbInfoArr *old_db_arr, DbInfoArr *new_db_arr, char *old_pgdata, char *new_pgdata, char *old_tablespace)
Definition: relfilenumber.c:86
#define MAX_STRING
Definition: pg_upgrade.h:22
#define vsnprintf
Definition: port.h:237
#define strerror
Definition: port.h:251
UserOpts user_opts
Definition: option.c:29
int jobs
Definition: pg_upgrade.h:297