git

1
#define USE_THE_REPOSITORY_VARIABLE
2

3
#include "git-compat-util.h"
4
#include "run-command.h"
5
#include "environment.h"
6
#include "exec-cmd.h"
7
#include "gettext.h"
8
#include "sigchain.h"
9
#include "strvec.h"
10
#include "symlinks.h"
11
#include "thread-utils.h"
12
#include "strbuf.h"
13
#include "string-list.h"
14
#include "trace.h"
15
#include "trace2.h"
16
#include "quote.h"
17
#include "config.h"
18
#include "packfile.h"
19
#include "compat/nonblock.h"
20

21
void child_process_init(struct child_process *child)
22
{
23
	struct child_process blank = CHILD_PROCESS_INIT;
24
	memcpy(child, &blank, sizeof(*child));
25
}
26

27
void child_process_clear(struct child_process *child)
28
{
29
	strvec_clear(&child->args);
30
	strvec_clear(&child->env);
31
}
32

33
struct child_to_clean {
34
	pid_t pid;
35
	struct child_process *process;
36
	struct child_to_clean *next;
37
};
38
static struct child_to_clean *children_to_clean;
39
static int installed_child_cleanup_handler;
40

41
static void cleanup_children(int sig, int in_signal)
42
{
43
	struct child_to_clean *children_to_wait_for = NULL;
44

45
	while (children_to_clean) {
46
		struct child_to_clean *p = children_to_clean;
47
		children_to_clean = p->next;
48

49
		if (p->process && !in_signal) {
50
			struct child_process *process = p->process;
51
			if (process->clean_on_exit_handler) {
52
				trace_printf(
53
					"trace: run_command: running exit handler for pid %"
54
					PRIuMAX, (uintmax_t)p->pid
55
				);
56
				process->clean_on_exit_handler(process);
57
			}
58
		}
59

60
		kill(p->pid, sig);
61

62
		if (p->process && p->process->wait_after_clean) {
63
			p->next = children_to_wait_for;
64
			children_to_wait_for = p;
65
		} else {
66
			if (!in_signal)
67
				free(p);
68
		}
69
	}
70

71
	while (children_to_wait_for) {
72
		struct child_to_clean *p = children_to_wait_for;
73
		children_to_wait_for = p->next;
74

75
		while (waitpid(p->pid, NULL, 0) < 0 && errno == EINTR)
76
			; /* spin waiting for process exit or error */
77

78
		if (!in_signal)
79
			free(p);
80
	}
81
}
82

83
static void cleanup_children_on_signal(int sig)
84
{
85
	cleanup_children(sig, 1);
86
	sigchain_pop(sig);
87
	raise(sig);
88
}
89

90
static void cleanup_children_on_exit(void)
91
{
92
	cleanup_children(SIGTERM, 0);
93
}
94

95
static void mark_child_for_cleanup(pid_t pid, struct child_process *process)
96
{
97
	struct child_to_clean *p = xmalloc(sizeof(*p));
98
	p->pid = pid;
99
	p->process = process;
100
	p->next = children_to_clean;
101
	children_to_clean = p;
102

103
	if (!installed_child_cleanup_handler) {
104
		atexit(cleanup_children_on_exit);
105
		sigchain_push_common(cleanup_children_on_signal);
106
		installed_child_cleanup_handler = 1;
107
	}
108
}
109

110
static void clear_child_for_cleanup(pid_t pid)
111
{
112
	struct child_to_clean **pp;
113

114
	for (pp = &children_to_clean; *pp; pp = &(*pp)->next) {
115
		struct child_to_clean *clean_me = *pp;
116

117
		if (clean_me->pid == pid) {
118
			*pp = clean_me->next;
119
			free(clean_me);
120
			return;
121
		}
122
	}
123
}
124

125
static inline void close_pair(int fd[2])
126
{
127
	close(fd[0]);
128
	close(fd[1]);
129
}
130

131
int is_executable(const char *name)
132
{
133
	struct stat st;
134

135
	if (stat(name, &st) || /* stat, not lstat */
136
	    !S_ISREG(st.st_mode))
137
		return 0;
138

139
#if defined(GIT_WINDOWS_NATIVE)
140
	/*
141
	 * On Windows there is no executable bit. The file extension
142
	 * indicates whether it can be run as an executable, and Git
143
	 * has special-handling to detect scripts and launch them
144
	 * through the indicated script interpreter. We test for the
145
	 * file extension first because virus scanners may make
146
	 * it quite expensive to open many files.
147
	 */
148
	if (ends_with(name, ".exe"))
149
		return S_IXUSR;
150

151
{
152
	/*
153
	 * Now that we know it does not have an executable extension,
154
	 * peek into the file instead.
155
	 */
156
	char buf[3] = { 0 };
157
	int n;
158
	int fd = open(name, O_RDONLY);
159
	st.st_mode &= ~S_IXUSR;
160
	if (fd >= 0) {
161
		n = read(fd, buf, 2);
162
		if (n == 2)
163
			/* look for a she-bang */
164
			if (!strcmp(buf, "#!"))
165
				st.st_mode |= S_IXUSR;
166
		close(fd);
167
	}
168
}
169
#endif
170
	return st.st_mode & S_IXUSR;
171
}
172

173
#ifndef locate_in_PATH
174
/*
175
 * Search $PATH for a command.  This emulates the path search that
176
 * execvp would perform, without actually executing the command so it
177
 * can be used before fork() to prepare to run a command using
178
 * execve() or after execvp() to diagnose why it failed.
179
 *
180
 * The caller should ensure that file contains no directory
181
 * separators.
182
 *
183
 * Returns the path to the command, as found in $PATH or NULL if the
184
 * command could not be found.  The caller inherits ownership of the memory
185
 * used to store the resultant path.
186
 *
187
 * This should not be used on Windows, where the $PATH search rules
188
 * are more complicated (e.g., a search for "foo" should find
189
 * "foo.exe").
190
 */
191
static char *locate_in_PATH(const char *file)
192
{
193
	const char *p = getenv("PATH");
194
	struct strbuf buf = STRBUF_INIT;
195

196
	if (!p || !*p)
197
		return NULL;
198

199
	while (1) {
200
		const char *end = strchrnul(p, ':');
201

202
		strbuf_reset(&buf);
203

204
		/* POSIX specifies an empty entry as the current directory. */
205
		if (end != p) {
206
			strbuf_add(&buf, p, end - p);
207
			strbuf_addch(&buf, '/');
208
		}
209
		strbuf_addstr(&buf, file);
210

211
		if (is_executable(buf.buf))
212
			return strbuf_detach(&buf, NULL);
213

214
		if (!*end)
215
			break;
216
		p = end + 1;
217
	}
218

219
	strbuf_release(&buf);
220
	return NULL;
221
}
222
#endif
223

224
int exists_in_PATH(const char *command)
225
{
226
	char *r = locate_in_PATH(command);
227
	int found = r != NULL;
228
	free(r);
229
	return found;
230
}
231

232
int sane_execvp(const char *file, char * const argv[])
233
{
234
#ifndef GIT_WINDOWS_NATIVE
235
	/*
236
	 * execvp() doesn't return, so we all we can do is tell trace2
237
	 * what we are about to do and let it leave a hint in the log
238
	 * (unless of course the execvp() fails).
239
	 *
240
	 * we skip this for Windows because the compat layer already
241
	 * has to emulate the execvp() call anyway.
242
	 */
243
	int exec_id = trace2_exec(file, (const char **)argv);
244
#endif
245

246
	if (!execvp(file, argv))
247
		return 0; /* cannot happen ;-) */
248

249
#ifndef GIT_WINDOWS_NATIVE
250
	{
251
		int ec = errno;
252
		trace2_exec_result(exec_id, ec);
253
		errno = ec;
254
	}
255
#endif
256

257
	/*
258
	 * When a command can't be found because one of the directories
259
	 * listed in $PATH is unsearchable, execvp reports EACCES, but
260
	 * careful usability testing (read: analysis of occasional bug
261
	 * reports) reveals that "No such file or directory" is more
262
	 * intuitive.
263
	 *
264
	 * We avoid commands with "/", because execvp will not do $PATH
265
	 * lookups in that case.
266
	 *
267
	 * The reassignment of EACCES to errno looks like a no-op below,
268
	 * but we need to protect against exists_in_PATH overwriting errno.
269
	 */
270
	if (errno == EACCES && !strchr(file, '/'))
271
		errno = exists_in_PATH(file) ? EACCES : ENOENT;
272
	else if (errno == ENOTDIR && !strchr(file, '/'))
273
		errno = ENOENT;
274
	return -1;
275
}
276

277
char *git_shell_path(void)
278
{
279
#ifndef GIT_WINDOWS_NATIVE
280
	return xstrdup(SHELL_PATH);
281
#else
282
	char *p = locate_in_PATH("sh");
283
	convert_slashes(p);
284
	return p;
285
#endif
286
}
287

288
static const char **prepare_shell_cmd(struct strvec *out, const char **argv)
289
{
290
	if (!argv[0])
291
		BUG("shell command is empty");
292

293
	if (strcspn(argv[0], "|&;<>()$`\\\"' \t\n*?[#~=%") != strlen(argv[0])) {
294
		strvec_push_nodup(out, git_shell_path());
295
		strvec_push(out, "-c");
296

297
		/*
298
		 * If we have no extra arguments, we do not even need to
299
		 * bother with the "$@" magic.
300
		 */
301
		if (!argv[1])
302
			strvec_push(out, argv[0]);
303
		else
304
			strvec_pushf(out, "%s \"$@\"", argv[0]);
305
	}
306

307
	strvec_pushv(out, argv);
308
	return out->v;
309
}
310

311
#ifndef GIT_WINDOWS_NATIVE
312
static int child_notifier = -1;
313

314
enum child_errcode {
315
	CHILD_ERR_CHDIR,
316
	CHILD_ERR_DUP2,
317
	CHILD_ERR_CLOSE,
318
	CHILD_ERR_SIGPROCMASK,
319
	CHILD_ERR_SILENT,
320
	CHILD_ERR_ERRNO
321
};
322

323
struct child_err {
324
	enum child_errcode err;
325
	int syserr; /* errno */
326
};
327

328
static void child_die(enum child_errcode err)
329
{
330
	struct child_err buf;
331

332
	buf.err = err;
333
	buf.syserr = errno;
334

335
	/* write(2) on buf smaller than PIPE_BUF (min 512) is atomic: */
336
	xwrite(child_notifier, &buf, sizeof(buf));
337
	_exit(1);
338
}
339

340
static void child_dup2(int fd, int to)
341
{
342
	if (dup2(fd, to) < 0)
343
		child_die(CHILD_ERR_DUP2);
344
}
345

346
static void child_close(int fd)
347
{
348
	if (close(fd))
349
		child_die(CHILD_ERR_CLOSE);
350
}
351

352
static void child_close_pair(int fd[2])
353
{
354
	child_close(fd[0]);
355
	child_close(fd[1]);
356
}
357

358
static void child_error_fn(const char *err UNUSED, va_list params UNUSED)
359
{
360
	const char msg[] = "error() should not be called in child\n";
361
	xwrite(2, msg, sizeof(msg) - 1);
362
}
363

364
static void child_warn_fn(const char *err UNUSED, va_list params UNUSED)
365
{
366
	const char msg[] = "warn() should not be called in child\n";
367
	xwrite(2, msg, sizeof(msg) - 1);
368
}
369

370
static void NORETURN child_die_fn(const char *err UNUSED, va_list params UNUSED)
371
{
372
	const char msg[] = "die() should not be called in child\n";
373
	xwrite(2, msg, sizeof(msg) - 1);
374
	_exit(2);
375
}
376

377
/* this runs in the parent process */
378
static void child_err_spew(struct child_process *cmd, struct child_err *cerr)
379
{
380
	static void (*old_errfn)(const char *err, va_list params);
381
	report_fn die_message_routine = get_die_message_routine();
382

383
	old_errfn = get_error_routine();
384
	set_error_routine(die_message_routine);
385
	errno = cerr->syserr;
386

387
	switch (cerr->err) {
388
	case CHILD_ERR_CHDIR:
389
		error_errno("exec '%s': cd to '%s' failed",
390
			    cmd->args.v[0], cmd->dir);
391
		break;
392
	case CHILD_ERR_DUP2:
393
		error_errno("dup2() in child failed");
394
		break;
395
	case CHILD_ERR_CLOSE:
396
		error_errno("close() in child failed");
397
		break;
398
	case CHILD_ERR_SIGPROCMASK:
399
		error_errno("sigprocmask failed restoring signals");
400
		break;
401
	case CHILD_ERR_SILENT:
402
		break;
403
	case CHILD_ERR_ERRNO:
404
		error_errno("cannot exec '%s'", cmd->args.v[0]);
405
		break;
406
	}
407
	set_error_routine(old_errfn);
408
}
409

410
static int prepare_cmd(struct strvec *out, const struct child_process *cmd)
411
{
412
	if (!cmd->args.v[0])
413
		BUG("command is empty");
414

415
	/*
416
	 * Add SHELL_PATH so in the event exec fails with ENOEXEC we can
417
	 * attempt to interpret the command with 'sh'.
418
	 */
419
	strvec_push(out, SHELL_PATH);
420

421
	if (cmd->git_cmd) {
422
		prepare_git_cmd(out, cmd->args.v);
423
	} else if (cmd->use_shell) {
424
		prepare_shell_cmd(out, cmd->args.v);
425
	} else {
426
		strvec_pushv(out, cmd->args.v);
427
	}
428

429
	/*
430
	 * If there are no dir separator characters in the command then perform
431
	 * a path lookup and use the resolved path as the command to exec. If
432
	 * there are dir separator characters, we have exec attempt to invoke
433
	 * the command directly.
434
	 */
435
	if (!has_dir_sep(out->v[1])) {
436
		char *program = locate_in_PATH(out->v[1]);
437
		if (program) {
438
			free((char *)out->v[1]);
439
			out->v[1] = program;
440
		} else {
441
			strvec_clear(out);
442
			errno = ENOENT;
443
			return -1;
444
		}
445
	}
446

447
	return 0;
448
}
449

450
static char **prep_childenv(const char *const *deltaenv)
451
{
452
	extern char **environ;
453
	char **childenv;
454
	struct string_list env = STRING_LIST_INIT_DUP;
455
	struct strbuf key = STRBUF_INIT;
456
	const char *const *p;
457
	int i;
458

459
	/* Construct a sorted string list consisting of the current environ */
460
	for (p = (const char *const *) environ; p && *p; p++) {
461
		const char *equals = strchr(*p, '=');
462

463
		if (equals) {
464
			strbuf_reset(&key);
465
			strbuf_add(&key, *p, equals - *p);
466
			string_list_append(&env, key.buf)->util = (void *) *p;
467
		} else {
468
			string_list_append(&env, *p)->util = (void *) *p;
469
		}
470
	}
471
	string_list_sort(&env);
472

473
	/* Merge in 'deltaenv' with the current environ */
474
	for (p = deltaenv; p && *p; p++) {
475
		const char *equals = strchr(*p, '=');
476

477
		if (equals) {
478
			/* ('key=value'), insert or replace entry */
479
			strbuf_reset(&key);
480
			strbuf_add(&key, *p, equals - *p);
481
			string_list_insert(&env, key.buf)->util = (void *) *p;
482
		} else {
483
			/* otherwise ('key') remove existing entry */
484
			string_list_remove(&env, *p, 0);
485
		}
486
	}
487

488
	/* Create an array of 'char *' to be used as the childenv */
489
	ALLOC_ARRAY(childenv, env.nr + 1);
490
	for (i = 0; i < env.nr; i++)
491
		childenv[i] = env.items[i].util;
492
	childenv[env.nr] = NULL;
493

494
	string_list_clear(&env, 0);
495
	strbuf_release(&key);
496
	return childenv;
497
}
498

499
struct atfork_state {
500
#ifndef NO_PTHREADS
501
	int cs;
502
#endif
503
	sigset_t old;
504
};
505

506
#define CHECK_BUG(err, msg) \
507
	do { \
508
		int e = (err); \
509
		if (e) \
510
			BUG("%s: %s", msg, strerror(e)); \
511
	} while(0)
512

513
static void atfork_prepare(struct atfork_state *as)
514
{
515
	sigset_t all;
516

517
	if (sigfillset(&all))
518
		die_errno("sigfillset");
519
#ifdef NO_PTHREADS
520
	if (sigprocmask(SIG_SETMASK, &all, &as->old))
521
		die_errno("sigprocmask");
522
#else
523
	CHECK_BUG(pthread_sigmask(SIG_SETMASK, &all, &as->old),
524
		"blocking all signals");
525
	CHECK_BUG(pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, &as->cs),
526
		"disabling cancellation");
527
#endif
528
}
529

530
static void atfork_parent(struct atfork_state *as)
531
{
532
#ifdef NO_PTHREADS
533
	if (sigprocmask(SIG_SETMASK, &as->old, NULL))
534
		die_errno("sigprocmask");
535
#else
536
	CHECK_BUG(pthread_setcancelstate(as->cs, NULL),
537
		"re-enabling cancellation");
538
	CHECK_BUG(pthread_sigmask(SIG_SETMASK, &as->old, NULL),
539
		"restoring signal mask");
540
#endif
541
}
542
#endif /* GIT_WINDOWS_NATIVE */
543

544
static inline void set_cloexec(int fd)
545
{
546
	int flags = fcntl(fd, F_GETFD);
547
	if (flags >= 0)
548
		fcntl(fd, F_SETFD, flags | FD_CLOEXEC);
549
}
550

551
static int wait_or_whine(pid_t pid, const char *argv0, int in_signal)
552
{
553
	int status, code = -1;
554
	pid_t waiting;
555
	int failed_errno = 0;
556

557
	while ((waiting = waitpid(pid, &status, 0)) < 0 && errno == EINTR)
558
		;	/* nothing */
559

560
	if (waiting < 0) {
561
		failed_errno = errno;
562
		if (!in_signal)
563
			error_errno("waitpid for %s failed", argv0);
564
	} else if (waiting != pid) {
565
		if (!in_signal)
566
			error("waitpid is confused (%s)", argv0);
567
	} else if (WIFSIGNALED(status)) {
568
		code = WTERMSIG(status);
569
		if (!in_signal && code != SIGINT && code != SIGQUIT && code != SIGPIPE)
570
			error("%s died of signal %d", argv0, code);
571
		/*
572
		 * This return value is chosen so that code & 0xff
573
		 * mimics the exit code that a POSIX shell would report for
574
		 * a program that died from this signal.
575
		 */
576
		code += 128;
577
	} else if (WIFEXITED(status)) {
578
		code = WEXITSTATUS(status);
579
	} else {
580
		if (!in_signal)
581
			error("waitpid is confused (%s)", argv0);
582
	}
583

584
	if (!in_signal)
585
		clear_child_for_cleanup(pid);
586

587
	errno = failed_errno;
588
	return code;
589
}
590

591
static void trace_add_env(struct strbuf *dst, const char *const *deltaenv)
592
{
593
	struct string_list envs = STRING_LIST_INIT_DUP;
594
	const char *const *e;
595
	int i;
596
	int printed_unset = 0;
597

598
	/* Last one wins, see run-command.c:prep_childenv() for context */
599
	for (e = deltaenv; e && *e; e++) {
600
		struct strbuf key = STRBUF_INIT;
601
		char *equals = strchr(*e, '=');
602

603
		if (equals) {
604
			strbuf_add(&key, *e, equals - *e);
605
			string_list_insert(&envs, key.buf)->util = equals + 1;
606
		} else {
607
			string_list_insert(&envs, *e)->util = NULL;
608
		}
609
		strbuf_release(&key);
610
	}
611

612
	/* "unset X Y...;" */
613
	for (i = 0; i < envs.nr; i++) {
614
		const char *var = envs.items[i].string;
615
		const char *val = envs.items[i].util;
616

617
		if (val || !getenv(var))
618
			continue;
619

620
		if (!printed_unset) {
621
			strbuf_addstr(dst, " unset");
622
			printed_unset = 1;
623
		}
624
		strbuf_addf(dst, " %s", var);
625
	}
626
	if (printed_unset)
627
		strbuf_addch(dst, ';');
628

629
	/* ... followed by "A=B C=D ..." */
630
	for (i = 0; i < envs.nr; i++) {
631
		const char *var = envs.items[i].string;
632
		const char *val = envs.items[i].util;
633
		const char *oldval;
634

635
		if (!val)
636
			continue;
637

638
		oldval = getenv(var);
639
		if (oldval && !strcmp(val, oldval))
640
			continue;
641

642
		strbuf_addf(dst, " %s=", var);
643
		sq_quote_buf_pretty(dst, val);
644
	}
645
	string_list_clear(&envs, 0);
646
}
647

648
static void trace_run_command(const struct child_process *cp)
649
{
650
	struct strbuf buf = STRBUF_INIT;
651

652
	if (!trace_want(&trace_default_key))
653
		return;
654

655
	strbuf_addstr(&buf, "trace: run_command:");
656
	if (cp->dir) {
657
		strbuf_addstr(&buf, " cd ");
658
		sq_quote_buf_pretty(&buf, cp->dir);
659
		strbuf_addch(&buf, ';');
660
	}
661
	trace_add_env(&buf, cp->env.v);
662
	if (cp->git_cmd)
663
		strbuf_addstr(&buf, " git");
664
	sq_quote_argv_pretty(&buf, cp->args.v);
665

666
	trace_printf("%s", buf.buf);
667
	strbuf_release(&buf);
668
}
669

670
int start_command(struct child_process *cmd)
671
{
672
	int need_in, need_out, need_err;
673
	int fdin[2], fdout[2], fderr[2];
674
	int failed_errno;
675
	const char *str;
676

677
	/*
678
	 * In case of errors we must keep the promise to close FDs
679
	 * that have been passed in via ->in and ->out.
680
	 */
681

682
	need_in = !cmd->no_stdin && cmd->in < 0;
683
	if (need_in) {
684
		if (pipe(fdin) < 0) {
685
			failed_errno = errno;
686
			if (cmd->out > 0)
687
				close(cmd->out);
688
			str = "standard input";
689
			goto fail_pipe;
690
		}
691
		cmd->in = fdin[1];
692
	}
693

694
	need_out = !cmd->no_stdout
695
		&& !cmd->stdout_to_stderr
696
		&& cmd->out < 0;
697
	if (need_out) {
698
		if (pipe(fdout) < 0) {
699
			failed_errno = errno;
700
			if (need_in)
701
				close_pair(fdin);
702
			else if (cmd->in)
703
				close(cmd->in);
704
			str = "standard output";
705
			goto fail_pipe;
706
		}
707
		cmd->out = fdout[0];
708
	}
709

710
	need_err = !cmd->no_stderr && cmd->err < 0;
711
	if (need_err) {
712
		if (pipe(fderr) < 0) {
713
			failed_errno = errno;
714
			if (need_in)
715
				close_pair(fdin);
716
			else if (cmd->in)
717
				close(cmd->in);
718
			if (need_out)
719
				close_pair(fdout);
720
			else if (cmd->out)
721
				close(cmd->out);
722
			str = "standard error";
723
fail_pipe:
724
			error("cannot create %s pipe for %s: %s",
725
				str, cmd->args.v[0], strerror(failed_errno));
726
			child_process_clear(cmd);
727
			errno = failed_errno;
728
			return -1;
729
		}
730
		cmd->err = fderr[0];
731
	}
732

733
	trace2_child_start(cmd);
734
	trace_run_command(cmd);
735

736
	fflush(NULL);
737

738
	if (cmd->close_object_store)
739
		close_object_store(the_repository->objects);
740

741
#ifndef GIT_WINDOWS_NATIVE
742
{
743
	int notify_pipe[2];
744
	int null_fd = -1;
745
	char **childenv;
746
	struct strvec argv = STRVEC_INIT;
747
	struct child_err cerr;
748
	struct atfork_state as;
749

750
	if (prepare_cmd(&argv, cmd) < 0) {
751
		failed_errno = errno;
752
		cmd->pid = -1;
753
		if (!cmd->silent_exec_failure)
754
			error_errno("cannot run %s", cmd->args.v[0]);
755
		goto end_of_spawn;
756
	}
757

758
	trace_argv_printf(&argv.v[1], "trace: start_command:");
759

760
	if (pipe(notify_pipe))
761
		notify_pipe[0] = notify_pipe[1] = -1;
762

763
	if (cmd->no_stdin || cmd->no_stdout || cmd->no_stderr) {
764
		null_fd = xopen("/dev/null", O_RDWR | O_CLOEXEC);
765
		set_cloexec(null_fd);
766
	}
767

768
	childenv = prep_childenv(cmd->env.v);
769
	atfork_prepare(&as);
770

771
	/*
772
	 * NOTE: In order to prevent deadlocking when using threads special
773
	 * care should be taken with the function calls made in between the
774
	 * fork() and exec() calls.  No calls should be made to functions which
775
	 * require acquiring a lock (e.g. malloc) as the lock could have been
776
	 * held by another thread at the time of forking, causing the lock to
777
	 * never be released in the child process.  This means only
778
	 * Async-Signal-Safe functions are permitted in the child.
779
	 */
780
	cmd->pid = fork();
781
	failed_errno = errno;
782
	if (!cmd->pid) {
783
		int sig;
784
		/*
785
		 * Ensure the default die/error/warn routines do not get
786
		 * called, they can take stdio locks and malloc.
787
		 */
788
		set_die_routine(child_die_fn);
789
		set_error_routine(child_error_fn);
790
		set_warn_routine(child_warn_fn);
791

792
		close(notify_pipe[0]);
793
		set_cloexec(notify_pipe[1]);
794
		child_notifier = notify_pipe[1];
795

796
		if (cmd->no_stdin)
797
			child_dup2(null_fd, 0);
798
		else if (need_in) {
799
			child_dup2(fdin[0], 0);
800
			child_close_pair(fdin);
801
		} else if (cmd->in) {
802
			child_dup2(cmd->in, 0);
803
			child_close(cmd->in);
804
		}
805

806
		if (cmd->no_stderr)
807
			child_dup2(null_fd, 2);
808
		else if (need_err) {
809
			child_dup2(fderr[1], 2);
810
			child_close_pair(fderr);
811
		} else if (cmd->err > 1) {
812
			child_dup2(cmd->err, 2);
813
			child_close(cmd->err);
814
		}
815

816
		if (cmd->no_stdout)
817
			child_dup2(null_fd, 1);
818
		else if (cmd->stdout_to_stderr)
819
			child_dup2(2, 1);
820
		else if (need_out) {
821
			child_dup2(fdout[1], 1);
822
			child_close_pair(fdout);
823
		} else if (cmd->out > 1) {
824
			child_dup2(cmd->out, 1);
825
			child_close(cmd->out);
826
		}
827

828
		if (cmd->dir && chdir(cmd->dir))
829
			child_die(CHILD_ERR_CHDIR);
830

831
		/*
832
		 * restore default signal handlers here, in case
833
		 * we catch a signal right before execve below
834
		 */
835
		for (sig = 1; sig < NSIG; sig++) {
836
			/* ignored signals get reset to SIG_DFL on execve */
837
			if (signal(sig, SIG_DFL) == SIG_IGN)
838
				signal(sig, SIG_IGN);
839
		}
840

841
		if (sigprocmask(SIG_SETMASK, &as.old, NULL) != 0)
842
			child_die(CHILD_ERR_SIGPROCMASK);
843

844
		/*
845
		 * Attempt to exec using the command and arguments starting at
846
		 * argv.argv[1].  argv.argv[0] contains SHELL_PATH which will
847
		 * be used in the event exec failed with ENOEXEC at which point
848
		 * we will try to interpret the command using 'sh'.
849
		 */
850
		execve(argv.v[1], (char *const *) argv.v + 1,
851
		       (char *const *) childenv);
852
		if (errno == ENOEXEC)
853
			execve(argv.v[0], (char *const *) argv.v,
854
			       (char *const *) childenv);
855

856
		if (cmd->silent_exec_failure && errno == ENOENT)
857
			child_die(CHILD_ERR_SILENT);
858
		child_die(CHILD_ERR_ERRNO);
859
	}
860
	atfork_parent(&as);
861
	if (cmd->pid < 0)
862
		error_errno("cannot fork() for %s", cmd->args.v[0]);
863
	else if (cmd->clean_on_exit)
864
		mark_child_for_cleanup(cmd->pid, cmd);
865

866
	/*
867
	 * Wait for child's exec. If the exec succeeds (or if fork()
868
	 * failed), EOF is seen immediately by the parent. Otherwise, the
869
	 * child process sends a child_err struct.
870
	 * Note that use of this infrastructure is completely advisory,
871
	 * therefore, we keep error checks minimal.
872
	 */
873
	close(notify_pipe[1]);
874
	if (xread(notify_pipe[0], &cerr, sizeof(cerr)) == sizeof(cerr)) {
875
		/*
876
		 * At this point we know that fork() succeeded, but exec()
877
		 * failed. Errors have been reported to our stderr.
878
		 */
879
		wait_or_whine(cmd->pid, cmd->args.v[0], 0);
880
		child_err_spew(cmd, &cerr);
881
		failed_errno = errno;
882
		cmd->pid = -1;
883
	}
884
	close(notify_pipe[0]);
885

886
	if (null_fd >= 0)
887
		close(null_fd);
888
	strvec_clear(&argv);
889
	free(childenv);
890
}
891
end_of_spawn:
892

893
#else
894
{
895
	int fhin = 0, fhout = 1, fherr = 2;
896
	const char **sargv = cmd->args.v;
897
	struct strvec nargv = STRVEC_INIT;
898

899
	if (cmd->no_stdin)
900
		fhin = open("/dev/null", O_RDWR);
901
	else if (need_in)
902
		fhin = dup(fdin[0]);
903
	else if (cmd->in)
904
		fhin = dup(cmd->in);
905

906
	if (cmd->no_stderr)
907
		fherr = open("/dev/null", O_RDWR);
908
	else if (need_err)
909
		fherr = dup(fderr[1]);
910
	else if (cmd->err > 2)
911
		fherr = dup(cmd->err);
912

913
	if (cmd->no_stdout)
914
		fhout = open("/dev/null", O_RDWR);
915
	else if (cmd->stdout_to_stderr)
916
		fhout = dup(fherr);
917
	else if (need_out)
918
		fhout = dup(fdout[1]);
919
	else if (cmd->out > 1)
920
		fhout = dup(cmd->out);
921

922
	if (cmd->git_cmd)
923
		cmd->args.v = prepare_git_cmd(&nargv, sargv);
924
	else if (cmd->use_shell)
925
		cmd->args.v = prepare_shell_cmd(&nargv, sargv);
926

927
	trace_argv_printf(cmd->args.v, "trace: start_command:");
928
	cmd->pid = mingw_spawnvpe(cmd->args.v[0], cmd->args.v,
929
				  (char**) cmd->env.v,
930
				  cmd->dir, fhin, fhout, fherr);
931
	failed_errno = errno;
932
	if (cmd->pid < 0 && (!cmd->silent_exec_failure || errno != ENOENT))
933
		error_errno("cannot spawn %s", cmd->args.v[0]);
934
	if (cmd->clean_on_exit && cmd->pid >= 0)
935
		mark_child_for_cleanup(cmd->pid, cmd);
936

937
	strvec_clear(&nargv);
938
	cmd->args.v = sargv;
939
	if (fhin != 0)
940
		close(fhin);
941
	if (fhout != 1)
942
		close(fhout);
943
	if (fherr != 2)
944
		close(fherr);
945
}
946
#endif
947

948
	if (cmd->pid < 0) {
949
		trace2_child_exit(cmd, -1);
950

951
		if (need_in)
952
			close_pair(fdin);
953
		else if (cmd->in)
954
			close(cmd->in);
955
		if (need_out)
956
			close_pair(fdout);
957
		else if (cmd->out)
958
			close(cmd->out);
959
		if (need_err)
960
			close_pair(fderr);
961
		else if (cmd->err)
962
			close(cmd->err);
963
		child_process_clear(cmd);
964
		errno = failed_errno;
965
		return -1;
966
	}
967

968
	if (need_in)
969
		close(fdin[0]);
970
	else if (cmd->in)
971
		close(cmd->in);
972

973
	if (need_out)
974
		close(fdout[1]);
975
	else if (cmd->out)
976
		close(cmd->out);
977

978
	if (need_err)
979
		close(fderr[1]);
980
	else if (cmd->err)
981
		close(cmd->err);
982

983
	return 0;
984
}
985

986
int finish_command(struct child_process *cmd)
987
{
988
	int ret = wait_or_whine(cmd->pid, cmd->args.v[0], 0);
989
	trace2_child_exit(cmd, ret);
990
	child_process_clear(cmd);
991
	invalidate_lstat_cache();
992
	return ret;
993
}
994

995
int finish_command_in_signal(struct child_process *cmd)
996
{
997
	int ret = wait_or_whine(cmd->pid, cmd->args.v[0], 1);
998
	if (ret != -1)
999
		trace2_child_exit(cmd, ret);
1000
	return ret;
1001
}
1002

1003

1004
int run_command(struct child_process *cmd)
1005
{
1006
	int code;
1007

1008
	if (cmd->out < 0 || cmd->err < 0)
1009
		BUG("run_command with a pipe can cause deadlock");
1010

1011
	code = start_command(cmd);
1012
	if (code)
1013
		return code;
1014
	return finish_command(cmd);
1015
}
1016

1017
#ifndef NO_PTHREADS
1018
static pthread_t main_thread;
1019
static int main_thread_set;
1020
static pthread_key_t async_key;
1021
static pthread_key_t async_die_counter;
1022

1023
static void *run_thread(void *data)
1024
{
1025
	struct async *async = data;
1026
	intptr_t ret;
1027

1028
	if (async->isolate_sigpipe) {
1029
		sigset_t mask;
1030
		sigemptyset(&mask);
1031
		sigaddset(&mask, SIGPIPE);
1032
		if (pthread_sigmask(SIG_BLOCK, &mask, NULL)) {
1033
			ret = error("unable to block SIGPIPE in async thread");
1034
			return (void *)ret;
1035
		}
1036
	}
1037

1038
	pthread_setspecific(async_key, async);
1039
	ret = async->proc(async->proc_in, async->proc_out, async->data);
1040
	return (void *)ret;
1041
}
1042

1043
static NORETURN void die_async(const char *err, va_list params)
1044
{
1045
	report_fn die_message_fn = get_die_message_routine();
1046

1047
	die_message_fn(err, params);
1048

1049
	if (in_async()) {
1050
		struct async *async = pthread_getspecific(async_key);
1051
		if (async->proc_in >= 0)
1052
			close(async->proc_in);
1053
		if (async->proc_out >= 0)
1054
			close(async->proc_out);
1055
		pthread_exit((void *)128);
1056
	}
1057

1058
	exit(128);
1059
}
1060

1061
static int async_die_is_recursing(void)
1062
{
1063
	void *ret = pthread_getspecific(async_die_counter);
1064
	pthread_setspecific(async_die_counter, &async_die_counter); /* set to any non-NULL valid pointer */
1065
	return ret != NULL;
1066
}
1067

1068
int in_async(void)
1069
{
1070
	if (!main_thread_set)
1071
		return 0; /* no asyncs started yet */
1072
	return !pthread_equal(main_thread, pthread_self());
1073
}
1074

1075
static void NORETURN async_exit(int code)
1076
{
1077
	pthread_exit((void *)(intptr_t)code);
1078
}
1079

1080
#else
1081

1082
static struct {
1083
	void (**handlers)(void);
1084
	size_t nr;
1085
	size_t alloc;
1086
} git_atexit_hdlrs;
1087

1088
static int git_atexit_installed;
1089

1090
static void git_atexit_dispatch(void)
1091
{
1092
	size_t i;
1093

1094
	for (i=git_atexit_hdlrs.nr ; i ; i--)
1095
		git_atexit_hdlrs.handlers[i-1]();
1096
}
1097

1098
static void git_atexit_clear(void)
1099
{
1100
	free(git_atexit_hdlrs.handlers);
1101
	memset(&git_atexit_hdlrs, 0, sizeof(git_atexit_hdlrs));
1102
	git_atexit_installed = 0;
1103
}
1104

1105
#undef atexit
1106
int git_atexit(void (*handler)(void))
1107
{
1108
	ALLOC_GROW(git_atexit_hdlrs.handlers, git_atexit_hdlrs.nr + 1, git_atexit_hdlrs.alloc);
1109
	git_atexit_hdlrs.handlers[git_atexit_hdlrs.nr++] = handler;
1110
	if (!git_atexit_installed) {
1111
		if (atexit(&git_atexit_dispatch))
1112
			return -1;
1113
		git_atexit_installed = 1;
1114
	}
1115
	return 0;
1116
}
1117
#define atexit git_atexit
1118

1119
static int process_is_async;
1120
int in_async(void)
1121
{
1122
	return process_is_async;
1123
}
1124

1125
static void NORETURN async_exit(int code)
1126
{
1127
	exit(code);
1128
}
1129

1130
#endif
1131

1132
void check_pipe(int err)
1133
{
1134
	if (err == EPIPE) {
1135
		if (in_async())
1136
			async_exit(141);
1137

1138
		signal(SIGPIPE, SIG_DFL);
1139
		raise(SIGPIPE);
1140
		/* Should never happen, but just in case... */
1141
		exit(141);
1142
	}
1143
}
1144

1145
int start_async(struct async *async)
1146
{
1147
	int need_in, need_out;
1148
	int fdin[2], fdout[2];
1149
	int proc_in, proc_out;
1150

1151
	need_in = async->in < 0;
1152
	if (need_in) {
1153
		if (pipe(fdin) < 0) {
1154
			if (async->out > 0)
1155
				close(async->out);
1156
			return error_errno("cannot create pipe");
1157
		}
1158
		async->in = fdin[1];
1159
	}
1160

1161
	need_out = async->out < 0;
1162
	if (need_out) {
1163
		if (pipe(fdout) < 0) {
1164
			if (need_in)
1165
				close_pair(fdin);
1166
			else if (async->in)
1167
				close(async->in);
1168
			return error_errno("cannot create pipe");
1169
		}
1170
		async->out = fdout[0];
1171
	}
1172

1173
	if (need_in)
1174
		proc_in = fdin[0];
1175
	else if (async->in)
1176
		proc_in = async->in;
1177
	else
1178
		proc_in = -1;
1179

1180
	if (need_out)
1181
		proc_out = fdout[1];
1182
	else if (async->out)
1183
		proc_out = async->out;
1184
	else
1185
		proc_out = -1;
1186

1187
#ifdef NO_PTHREADS
1188
	/* Flush stdio before fork() to avoid cloning buffers */
1189
	fflush(NULL);
1190

1191
	async->pid = fork();
1192
	if (async->pid < 0) {
1193
		error_errno("fork (async) failed");
1194
		goto error;
1195
	}
1196
	if (!async->pid) {
1197
		if (need_in)
1198
			close(fdin[1]);
1199
		if (need_out)
1200
			close(fdout[0]);
1201
		git_atexit_clear();
1202
		process_is_async = 1;
1203
		exit(!!async->proc(proc_in, proc_out, async->data));
1204
	}
1205

1206
	mark_child_for_cleanup(async->pid, NULL);
1207

1208
	if (need_in)
1209
		close(fdin[0]);
1210
	else if (async->in)
1211
		close(async->in);
1212

1213
	if (need_out)
1214
		close(fdout[1]);
1215
	else if (async->out)
1216
		close(async->out);
1217
#else
1218
	if (!main_thread_set) {
1219
		/*
1220
		 * We assume that the first time that start_async is called
1221
		 * it is from the main thread.
1222
		 */
1223
		main_thread_set = 1;
1224
		main_thread = pthread_self();
1225
		pthread_key_create(&async_key, NULL);
1226
		pthread_key_create(&async_die_counter, NULL);
1227
		set_die_routine(die_async);
1228
		set_die_is_recursing_routine(async_die_is_recursing);
1229
	}
1230

1231
	if (proc_in >= 0)
1232
		set_cloexec(proc_in);
1233
	if (proc_out >= 0)
1234
		set_cloexec(proc_out);
1235
	async->proc_in = proc_in;
1236
	async->proc_out = proc_out;
1237
	{
1238
		int err = pthread_create(&async->tid, NULL, run_thread, async);
1239
		if (err) {
1240
			error(_("cannot create async thread: %s"), strerror(err));
1241
			goto error;
1242
		}
1243
	}
1244
#endif
1245
	return 0;
1246

1247
error:
1248
	if (need_in)
1249
		close_pair(fdin);
1250
	else if (async->in)
1251
		close(async->in);
1252

1253
	if (need_out)
1254
		close_pair(fdout);
1255
	else if (async->out)
1256
		close(async->out);
1257
	return -1;
1258
}
1259

1260
int finish_async(struct async *async)
1261
{
1262
#ifdef NO_PTHREADS
1263
	int ret = wait_or_whine(async->pid, "child process", 0);
1264

1265
	invalidate_lstat_cache();
1266

1267
	return ret;
1268
#else
1269
	void *ret = (void *)(intptr_t)(-1);
1270

1271
	if (pthread_join(async->tid, &ret))
1272
		error("pthread_join failed");
1273
	invalidate_lstat_cache();
1274
	return (int)(intptr_t)ret;
1275

1276
#endif
1277
}
1278

1279
int async_with_fork(void)
1280
{
1281
#ifdef NO_PTHREADS
1282
	return 1;
1283
#else
1284
	return 0;
1285
#endif
1286
}
1287

1288
struct io_pump {
1289
	/* initialized by caller */
1290
	int fd;
1291
	int type; /* POLLOUT or POLLIN */
1292
	union {
1293
		struct {
1294
			const char *buf;
1295
			size_t len;
1296
		} out;
1297
		struct {
1298
			struct strbuf *buf;
1299
			size_t hint;
1300
		} in;
1301
	} u;
1302

1303
	/* returned by pump_io */
1304
	int error; /* 0 for success, otherwise errno */
1305

1306
	/* internal use */
1307
	struct pollfd *pfd;
1308
};
1309

1310
static int pump_io_round(struct io_pump *slots, int nr, struct pollfd *pfd)
1311
{
1312
	int pollsize = 0;
1313
	int i;
1314

1315
	for (i = 0; i < nr; i++) {
1316
		struct io_pump *io = &slots[i];
1317
		if (io->fd < 0)
1318
			continue;
1319
		pfd[pollsize].fd = io->fd;
1320
		pfd[pollsize].events = io->type;
1321
		io->pfd = &pfd[pollsize++];
1322
	}
1323

1324
	if (!pollsize)
1325
		return 0;
1326

1327
	if (poll(pfd, pollsize, -1) < 0) {
1328
		if (errno == EINTR)
1329
			return 1;
1330
		die_errno("poll failed");
1331
	}
1332

1333
	for (i = 0; i < nr; i++) {
1334
		struct io_pump *io = &slots[i];
1335

1336
		if (io->fd < 0)
1337
			continue;
1338

1339
		if (!(io->pfd->revents & (POLLOUT|POLLIN|POLLHUP|POLLERR|POLLNVAL)))
1340
			continue;
1341

1342
		if (io->type == POLLOUT) {
1343
			ssize_t len;
1344

1345
			/*
1346
			 * Don't use xwrite() here. It loops forever on EAGAIN,
1347
			 * and we're in our own poll() loop here.
1348
			 *
1349
			 * Note that we lose xwrite()'s handling of MAX_IO_SIZE
1350
			 * and EINTR, so we have to implement those ourselves.
1351
			 */
1352
			len = write(io->fd, io->u.out.buf,
1353
				    io->u.out.len <= MAX_IO_SIZE ?
1354
				    io->u.out.len : MAX_IO_SIZE);
1355
			if (len < 0) {
1356
				if (errno != EINTR && errno != EAGAIN &&
1357
				    errno != ENOSPC) {
1358
					io->error = errno;
1359
					close(io->fd);
1360
					io->fd = -1;
1361
				}
1362
			} else {
1363
				io->u.out.buf += len;
1364
				io->u.out.len -= len;
1365
				if (!io->u.out.len) {
1366
					close(io->fd);
1367
					io->fd = -1;
1368
				}
1369
			}
1370
		}
1371

1372
		if (io->type == POLLIN) {
1373
			ssize_t len = strbuf_read_once(io->u.in.buf,
1374
						       io->fd, io->u.in.hint);
1375
			if (len < 0)
1376
				io->error = errno;
1377
			if (len <= 0) {
1378
				close(io->fd);
1379
				io->fd = -1;
1380
			}
1381
		}
1382
	}
1383

1384
	return 1;
1385
}
1386

1387
static int pump_io(struct io_pump *slots, int nr)
1388
{
1389
	struct pollfd *pfd;
1390
	int i;
1391

1392
	for (i = 0; i < nr; i++)
1393
		slots[i].error = 0;
1394

1395
	ALLOC_ARRAY(pfd, nr);
1396
	while (pump_io_round(slots, nr, pfd))
1397
		; /* nothing */
1398
	free(pfd);
1399

1400
	/* There may be multiple errno values, so just pick the first. */
1401
	for (i = 0; i < nr; i++) {
1402
		if (slots[i].error) {
1403
			errno = slots[i].error;
1404
			return -1;
1405
		}
1406
	}
1407
	return 0;
1408
}
1409

1410

1411
int pipe_command(struct child_process *cmd,
1412
		 const char *in, size_t in_len,
1413
		 struct strbuf *out, size_t out_hint,
1414
		 struct strbuf *err, size_t err_hint)
1415
{
1416
	struct io_pump io[3];
1417
	int nr = 0;
1418

1419
	if (in)
1420
		cmd->in = -1;
1421
	if (out)
1422
		cmd->out = -1;
1423
	if (err)
1424
		cmd->err = -1;
1425

1426
	if (start_command(cmd) < 0)
1427
		return -1;
1428

1429
	if (in) {
1430
		if (enable_pipe_nonblock(cmd->in) < 0) {
1431
			error_errno("unable to make pipe non-blocking");
1432
			close(cmd->in);
1433
			if (out)
1434
				close(cmd->out);
1435
			if (err)
1436
				close(cmd->err);
1437
			return -1;
1438
		}
1439
		io[nr].fd = cmd->in;
1440
		io[nr].type = POLLOUT;
1441
		io[nr].u.out.buf = in;
1442
		io[nr].u.out.len = in_len;
1443
		nr++;
1444
	}
1445
	if (out) {
1446
		io[nr].fd = cmd->out;
1447
		io[nr].type = POLLIN;
1448
		io[nr].u.in.buf = out;
1449
		io[nr].u.in.hint = out_hint;
1450
		nr++;
1451
	}
1452
	if (err) {
1453
		io[nr].fd = cmd->err;
1454
		io[nr].type = POLLIN;
1455
		io[nr].u.in.buf = err;
1456
		io[nr].u.in.hint = err_hint;
1457
		nr++;
1458
	}
1459

1460
	if (pump_io(io, nr) < 0) {
1461
		finish_command(cmd); /* throw away exit code */
1462
		return -1;
1463
	}
1464

1465
	return finish_command(cmd);
1466
}
1467

1468
enum child_state {
1469
	GIT_CP_FREE,
1470
	GIT_CP_WORKING,
1471
	GIT_CP_WAIT_CLEANUP,
1472
};
1473

1474
struct parallel_processes {
1475
	size_t nr_processes;
1476

1477
	struct {
1478
		enum child_state state;
1479
		struct child_process process;
1480
		struct strbuf err;
1481
		void *data;
1482
	} *children;
1483
	/*
1484
	 * The struct pollfd is logically part of *children,
1485
	 * but the system call expects it as its own array.
1486
	 */
1487
	struct pollfd *pfd;
1488

1489
	unsigned shutdown : 1;
1490

1491
	size_t output_owner;
1492
	struct strbuf buffered_output; /* of finished children */
1493
};
1494

1495
struct parallel_processes_for_signal {
1496
	const struct run_process_parallel_opts *opts;
1497
	const struct parallel_processes *pp;
1498
};
1499

1500
static void kill_children(const struct parallel_processes *pp,
1501
			  const struct run_process_parallel_opts *opts,
1502
			  int signo)
1503
{
1504
	for (size_t i = 0; i < opts->processes; i++)
1505
		if (pp->children[i].state == GIT_CP_WORKING)
1506
			kill(pp->children[i].process.pid, signo);
1507
}
1508

1509
static void kill_children_signal(const struct parallel_processes_for_signal *pp_sig,
1510
				 int signo)
1511
{
1512
	kill_children(pp_sig->pp, pp_sig->opts, signo);
1513
}
1514

1515
static struct parallel_processes_for_signal *pp_for_signal;
1516

1517
static void handle_children_on_signal(int signo)
1518
{
1519
	kill_children_signal(pp_for_signal, signo);
1520
	sigchain_pop(signo);
1521
	raise(signo);
1522
}
1523

1524
static void pp_init(struct parallel_processes *pp,
1525
		    const struct run_process_parallel_opts *opts,
1526
		    struct parallel_processes_for_signal *pp_sig)
1527
{
1528
	const size_t n = opts->processes;
1529

1530
	if (!n)
1531
		BUG("you must provide a non-zero number of processes!");
1532

1533
	trace_printf("run_processes_parallel: preparing to run up to %"PRIuMAX" tasks",
1534
		     (uintmax_t)n);
1535

1536
	if (!opts->get_next_task)
1537
		BUG("you need to specify a get_next_task function");
1538

1539
	CALLOC_ARRAY(pp->children, n);
1540
	if (!opts->ungroup)
1541
		CALLOC_ARRAY(pp->pfd, n);
1542

1543
	for (size_t i = 0; i < n; i++) {
1544
		strbuf_init(&pp->children[i].err, 0);
1545
		child_process_init(&pp->children[i].process);
1546
		if (pp->pfd) {
1547
			pp->pfd[i].events = POLLIN | POLLHUP;
1548
			pp->pfd[i].fd = -1;
1549
		}
1550
	}
1551

1552
	pp_sig->pp = pp;
1553
	pp_sig->opts = opts;
1554
	pp_for_signal = pp_sig;
1555
	sigchain_push_common(handle_children_on_signal);
1556
}
1557

1558
static void pp_cleanup(struct parallel_processes *pp,
1559
		       const struct run_process_parallel_opts *opts)
1560
{
1561
	trace_printf("run_processes_parallel: done");
1562
	for (size_t i = 0; i < opts->processes; i++) {
1563
		strbuf_release(&pp->children[i].err);
1564
		child_process_clear(&pp->children[i].process);
1565
	}
1566

1567
	free(pp->children);
1568
	free(pp->pfd);
1569

1570
	/*
1571
	 * When get_next_task added messages to the buffer in its last
1572
	 * iteration, the buffered output is non empty.
1573
	 */
1574
	strbuf_write(&pp->buffered_output, stderr);
1575
	strbuf_release(&pp->buffered_output);
1576

1577
	sigchain_pop_common();
1578
}
1579

1580
/* returns
1581
 *  0 if a new task was started.
1582
 *  1 if no new jobs was started (get_next_task ran out of work, non critical
1583
 *    problem with starting a new command)
1584
 * <0 no new job was started, user wishes to shutdown early. Use negative code
1585
 *    to signal the children.
1586
 */
1587
static int pp_start_one(struct parallel_processes *pp,
1588
			const struct run_process_parallel_opts *opts)
1589
{
1590
	size_t i;
1591
	int code;
1592

1593
	for (i = 0; i < opts->processes; i++)
1594
		if (pp->children[i].state == GIT_CP_FREE)
1595
			break;
1596
	if (i == opts->processes)
1597
		BUG("bookkeeping is hard");
1598

1599
	/*
1600
	 * By default, do not inherit stdin from the parent process - otherwise,
1601
	 * all children would share stdin! Users may overwrite this to provide
1602
	 * something to the child's stdin by having their 'get_next_task'
1603
	 * callback assign 0 to .no_stdin and an appropriate integer to .in.
1604
	 */
1605
	pp->children[i].process.no_stdin = 1;
1606

1607
	code = opts->get_next_task(&pp->children[i].process,
1608
				   opts->ungroup ? NULL : &pp->children[i].err,
1609
				   opts->data,
1610
				   &pp->children[i].data);
1611
	if (!code) {
1612
		if (!opts->ungroup) {
1613
			strbuf_addbuf(&pp->buffered_output, &pp->children[i].err);
1614
			strbuf_reset(&pp->children[i].err);
1615
		}
1616
		return 1;
1617
	}
1618
	if (!opts->ungroup) {
1619
		pp->children[i].process.err = -1;
1620
		pp->children[i].process.stdout_to_stderr = 1;
1621
	}
1622

1623
	if (start_command(&pp->children[i].process)) {
1624
		if (opts->start_failure)
1625
			code = opts->start_failure(opts->ungroup ? NULL :
1626
						   &pp->children[i].err,
1627
						   opts->data,
1628
						   pp->children[i].data);
1629
		else
1630
			code = 0;
1631

1632
		if (!opts->ungroup) {
1633
			strbuf_addbuf(&pp->buffered_output, &pp->children[i].err);
1634
			strbuf_reset(&pp->children[i].err);
1635
		}
1636
		if (code)
1637
			pp->shutdown = 1;
1638
		return code;
1639
	}
1640

1641
	pp->nr_processes++;
1642
	pp->children[i].state = GIT_CP_WORKING;
1643
	if (pp->pfd)
1644
		pp->pfd[i].fd = pp->children[i].process.err;
1645
	return 0;
1646
}
1647

1648
static void pp_buffer_stderr(struct parallel_processes *pp,
1649
			     const struct run_process_parallel_opts *opts,
1650
			     int output_timeout)
1651
{
1652
	while (poll(pp->pfd, opts->processes, output_timeout) < 0) {
1653
		if (errno == EINTR)
1654
			continue;
1655
		pp_cleanup(pp, opts);
1656
		die_errno("poll");
1657
	}
1658

1659
	/* Buffer output from all pipes. */
1660
	for (size_t i = 0; i < opts->processes; i++) {
1661
		if (pp->children[i].state == GIT_CP_WORKING &&
1662
		    pp->pfd[i].revents & (POLLIN | POLLHUP)) {
1663
			int n = strbuf_read_once(&pp->children[i].err,
1664
						 pp->children[i].process.err, 0);
1665
			if (n == 0) {
1666
				close(pp->children[i].process.err);
1667
				pp->children[i].state = GIT_CP_WAIT_CLEANUP;
1668
			} else if (n < 0)
1669
				if (errno != EAGAIN)
1670
					die_errno("read");
1671
		}
1672
	}
1673
}
1674

1675
static void pp_output(const struct parallel_processes *pp)
1676
{
1677
	size_t i = pp->output_owner;
1678

1679
	if (pp->children[i].state == GIT_CP_WORKING &&
1680
	    pp->children[i].err.len) {
1681
		strbuf_write(&pp->children[i].err, stderr);
1682
		strbuf_reset(&pp->children[i].err);
1683
	}
1684
}
1685

1686
static int pp_collect_finished(struct parallel_processes *pp,
1687
			       const struct run_process_parallel_opts *opts)
1688
{
1689
	int code;
1690
	size_t i;
1691
	int result = 0;
1692

1693
	while (pp->nr_processes > 0) {
1694
		for (i = 0; i < opts->processes; i++)
1695
			if (pp->children[i].state == GIT_CP_WAIT_CLEANUP)
1696
				break;
1697
		if (i == opts->processes)
1698
			break;
1699

1700
		code = finish_command(&pp->children[i].process);
1701

1702
		if (opts->task_finished)
1703
			code = opts->task_finished(code, opts->ungroup ? NULL :
1704
						   &pp->children[i].err, opts->data,
1705
						   pp->children[i].data);
1706
		else
1707
			code = 0;
1708

1709
		if (code)
1710
			result = code;
1711
		if (code < 0)
1712
			break;
1713

1714
		pp->nr_processes--;
1715
		pp->children[i].state = GIT_CP_FREE;
1716
		if (pp->pfd)
1717
			pp->pfd[i].fd = -1;
1718
		child_process_init(&pp->children[i].process);
1719

1720
		if (opts->ungroup) {
1721
			; /* no strbuf_*() work to do here */
1722
		} else if (i != pp->output_owner) {
1723
			strbuf_addbuf(&pp->buffered_output, &pp->children[i].err);
1724
			strbuf_reset(&pp->children[i].err);
1725
		} else {
1726
			const size_t n = opts->processes;
1727

1728
			strbuf_write(&pp->children[i].err, stderr);
1729
			strbuf_reset(&pp->children[i].err);
1730

1731
			/* Output all other finished child processes */
1732
			strbuf_write(&pp->buffered_output, stderr);
1733
			strbuf_reset(&pp->buffered_output);
1734

1735
			/*
1736
			 * Pick next process to output live.
1737
			 * NEEDSWORK:
1738
			 * For now we pick it randomly by doing a round
1739
			 * robin. Later we may want to pick the one with
1740
			 * the most output or the longest or shortest
1741
			 * running process time.
1742
			 */
1743
			for (i = 0; i < n; i++)
1744
				if (pp->children[(pp->output_owner + i) % n].state == GIT_CP_WORKING)
1745
					break;
1746
			pp->output_owner = (pp->output_owner + i) % n;
1747
		}
1748
	}
1749
	return result;
1750
}
1751

1752
void run_processes_parallel(const struct run_process_parallel_opts *opts)
1753
{
1754
	int i, code;
1755
	int output_timeout = 100;
1756
	int spawn_cap = 4;
1757
	struct parallel_processes_for_signal pp_sig;
1758
	struct parallel_processes pp = {
1759
		.buffered_output = STRBUF_INIT,
1760
	};
1761
	/* options */
1762
	const char *tr2_category = opts->tr2_category;
1763
	const char *tr2_label = opts->tr2_label;
1764
	const int do_trace2 = tr2_category && tr2_label;
1765

1766
	if (do_trace2)
1767
		trace2_region_enter_printf(tr2_category, tr2_label, NULL,
1768
					   "max:%"PRIuMAX,
1769
					   (uintmax_t)opts->processes);
1770

1771
	pp_init(&pp, opts, &pp_sig);
1772
	while (1) {
1773
		for (i = 0;
1774
		    i < spawn_cap && !pp.shutdown &&
1775
		    pp.nr_processes < opts->processes;
1776
		    i++) {
1777
			code = pp_start_one(&pp, opts);
1778
			if (!code)
1779
				continue;
1780
			if (code < 0) {
1781
				pp.shutdown = 1;
1782
				kill_children(&pp, opts, -code);
1783
			}
1784
			break;
1785
		}
1786
		if (!pp.nr_processes)
1787
			break;
1788
		if (opts->ungroup) {
1789
			for (size_t i = 0; i < opts->processes; i++)
1790
				pp.children[i].state = GIT_CP_WAIT_CLEANUP;
1791
		} else {
1792
			pp_buffer_stderr(&pp, opts, output_timeout);
1793
			pp_output(&pp);
1794
		}
1795
		code = pp_collect_finished(&pp, opts);
1796
		if (code) {
1797
			pp.shutdown = 1;
1798
			if (code < 0)
1799
				kill_children(&pp, opts,-code);
1800
		}
1801
	}
1802

1803
	pp_cleanup(&pp, opts);
1804

1805
	if (do_trace2)
1806
		trace2_region_leave(tr2_category, tr2_label, NULL);
1807
}
1808

1809
int prepare_auto_maintenance(int quiet, struct child_process *maint)
1810
{
1811
	int enabled, auto_detach;
1812

1813
	if (!git_config_get_bool("maintenance.auto", &enabled) &&
1814
	    !enabled)
1815
		return 0;
1816

1817
	/*
1818
	 * When `maintenance.autoDetach` isn't set, then we fall back to
1819
	 * honoring `gc.autoDetach`. This is somewhat weird, but required to
1820
	 * retain behaviour from when we used to run git-gc(1) here.
1821
	 */
1822
	if (git_config_get_bool("maintenance.autodetach", &auto_detach) &&
1823
	    git_config_get_bool("gc.autodetach", &auto_detach))
1824
		auto_detach = 1;
1825

1826
	maint->git_cmd = 1;
1827
	maint->close_object_store = 1;
1828
	strvec_pushl(&maint->args, "maintenance", "run", "--auto", NULL);
1829
	strvec_push(&maint->args, quiet ? "--quiet" : "--no-quiet");
1830
	strvec_push(&maint->args, auto_detach ? "--detach" : "--no-detach");
1831

1832
	return 1;
1833
}
1834

1835
int run_auto_maintenance(int quiet)
1836
{
1837
	struct child_process maint = CHILD_PROCESS_INIT;
1838
	if (!prepare_auto_maintenance(quiet, &maint))
1839
		return 0;
1840
	return run_command(&maint);
1841
}
1842

1843
void prepare_other_repo_env(struct strvec *env, const char *new_git_dir)
1844
{
1845
	const char * const *var;
1846

1847
	for (var = local_repo_env; *var; var++) {
1848
		if (strcmp(*var, CONFIG_DATA_ENVIRONMENT) &&
1849
		    strcmp(*var, CONFIG_COUNT_ENVIRONMENT))
1850
			strvec_push(env, *var);
1851
	}
1852
	strvec_pushf(env, "%s=%s", GIT_DIR_ENVIRONMENT, new_git_dir);
1853
}
1854

1855
enum start_bg_result start_bg_command(struct child_process *cmd,
1856
				      start_bg_wait_cb *wait_cb,
1857
				      void *cb_data,
1858
				      unsigned int timeout_sec)
1859
{
1860
	enum start_bg_result sbgr = SBGR_ERROR;
1861
	int ret;
1862
	int wait_status;
1863
	pid_t pid_seen;
1864
	time_t time_limit;
1865

1866
	/*
1867
	 * We do not allow clean-on-exit because the child process
1868
	 * should persist in the background and possibly/probably
1869
	 * after this process exits.  So we don't want to kill the
1870
	 * child during our atexit routine.
1871
	 */
1872
	if (cmd->clean_on_exit)
1873
		BUG("start_bg_command() does not allow non-zero clean_on_exit");
1874

1875
	if (!cmd->trace2_child_class)
1876
		cmd->trace2_child_class = "background";
1877

1878
	ret = start_command(cmd);
1879
	if (ret) {
1880
		/*
1881
		 * We assume that if `start_command()` fails, we
1882
		 * either get a complete `trace2_child_start() /
1883
		 * trace2_child_exit()` pair or it fails before the
1884
		 * `trace2_child_start()` is emitted, so we do not
1885
		 * need to worry about it here.
1886
		 *
1887
		 * We also assume that `start_command()` does not add
1888
		 * us to the cleanup list.  And that it calls
1889
		 * `child_process_clear()`.
1890
		 */
1891
		sbgr = SBGR_ERROR;
1892
		goto done;
1893
	}
1894

1895
	time(&time_limit);
1896
	time_limit += timeout_sec;
1897

1898
wait:
1899
	pid_seen = waitpid(cmd->pid, &wait_status, WNOHANG);
1900

1901
	if (!pid_seen) {
1902
		/*
1903
		 * The child is currently running.  Ask the callback
1904
		 * if the child is ready to do work or whether we
1905
		 * should keep waiting for it to boot up.
1906
		 */
1907
		ret = (*wait_cb)(cmd, cb_data);
1908
		if (!ret) {
1909
			/*
1910
			 * The child is running and "ready".
1911
			 */
1912
			trace2_child_ready(cmd, "ready");
1913
			sbgr = SBGR_READY;
1914
			goto done;
1915
		} else if (ret > 0) {
1916
			/*
1917
			 * The callback said to give it more time to boot up
1918
			 * (subject to our timeout limit).
1919
			 */
1920
			time_t now;
1921

1922
			time(&now);
1923
			if (now < time_limit)
1924
				goto wait;
1925

1926
			/*
1927
			 * Our timeout has expired.  We don't try to
1928
			 * kill the child, but rather let it continue
1929
			 * (hopefully) trying to startup.
1930
			 */
1931
			trace2_child_ready(cmd, "timeout");
1932
			sbgr = SBGR_TIMEOUT;
1933
			goto done;
1934
		} else {
1935
			/*
1936
			 * The cb gave up on this child.  It is still running,
1937
			 * but our cb got an error trying to probe it.
1938
			 */
1939
			trace2_child_ready(cmd, "error");
1940
			sbgr = SBGR_CB_ERROR;
1941
			goto done;
1942
		}
1943
	}
1944

1945
	else if (pid_seen == cmd->pid) {
1946
		int child_code = -1;
1947

1948
		/*
1949
		 * The child started, but exited or was terminated
1950
		 * before becoming "ready".
1951
		 *
1952
		 * We try to match the behavior of `wait_or_whine()`
1953
		 * WRT the handling of WIFSIGNALED() and WIFEXITED()
1954
		 * and convert the child's status to a return code for
1955
		 * tracing purposes and emit the `trace2_child_exit()`
1956
		 * event.
1957
		 *
1958
		 * We do not want the wait_or_whine() error message
1959
		 * because we will be called by client-side library
1960
		 * routines.
1961
		 */
1962
		if (WIFEXITED(wait_status))
1963
			child_code = WEXITSTATUS(wait_status);
1964
		else if (WIFSIGNALED(wait_status))
1965
			child_code = WTERMSIG(wait_status) + 128;
1966
		trace2_child_exit(cmd, child_code);
1967

1968
		sbgr = SBGR_DIED;
1969
		goto done;
1970
	}
1971

1972
	else if (pid_seen < 0 && errno == EINTR)
1973
		goto wait;
1974

1975
	trace2_child_exit(cmd, -1);
1976
	sbgr = SBGR_ERROR;
1977

1978
done:
1979
	child_process_clear(cmd);
1980
	invalidate_lstat_cache();
1981
	return sbgr;
1982
}
1983