posix_spawn(p) returns before the spawned process is fully up and running. As a
result, the spawned process can fail to receive signals. The attached test case
illustrates the problem. It spawns a sleep process and then tries to kill it.
On exit, the sleep process is still running.
The following excerpts from the strace output show the issue: The SIGTERM signal
is sent after the main program has forked a subprocess (and posix_spawnp has
returned), but before the forked subprocess has exec'd the sleep process:
559 32069 [main] spawn_test 4125 vfork: stub called
257 48437 [main] spawn_test 4125 dofork: 4126 = fork()
754 9511 [main] spawn_test 4126 dofork: 0 = fork()
66 48503 [main] spawn_test 4125 kill0: kill (4126, 15)
44 9555 [main] spawn_test 4126 find_exec: find_exec (/usr/bin/sleep)
42 10835 [main] spawn_test 4126 spawnve: spawnve (/usr/bin/sleep, sleep,
0x8000281A0)
45 3149 [main] sleep 4126 child_info::ready: signalled 0x164 that I was
ready
6475 21055 [main] spawn_test 4126! child_info::sync: pid 45028, WFMO
returned 0, exit_code 0x103, res 1
--- Process 45028 (pid: 4126) thread 41444 created
Ken
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <spawn.h>
#include <signal.h>
extern char **environ;
pid_t
run_sleep ()
{
pid_t pid;
char *argv[] = { "sleep", "3600", NULL };
int err = posix_spawnp (&pid, "/usr/bin/sleep", NULL, NULL, argv, environ);
if (err == 0)
return pid;
else
{
printf ("posix_spawnp: %s\n", strerror (err));
exit (1);
}
}
int
main ()
{
pid_t pid = run_sleep ();
kill (pid, SIGTERM);
}
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