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More graceful handling of setpgid(2) failure in child_set_group()

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Handle EPERM (WSL only?) and EINTR by retrying.
This commit is contained in:
Mahmoud Al-Qudsi 2018-10-09 14:37:11 -05:00
parent 3afcca3114
commit c7f5e58927
1 changed files with 25 additions and 5 deletions
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30
src/postfork.cpp
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@ -63,12 +63,31 @@ static void debug_safe_int(int level, const char *format, int val) {
/// process if it is the first in a JOB_CONTROL job.
/// Returns true on sucess, false on failiure.
bool child_set_group(job_t *j, process_t *p) {
bool retval = true;
if (j->get_flag(job_flag_t::JOB_CONTROL)) {
if (j->pgid == INVALID_PID) {
j->pgid = p->pid;
}
if (setpgid(p->pid, j->pgid) < 0) {
for (int i = 0; setpgid(p->pid, j->pgid) != 0; ++i) {
// Put a cap on how many times we retry so we are never stuck here
if (i < 100) {
if (errno == EPERM) {
// The setpgid(2) man page says that EPERM is returned only if attempts are made to
// move processes into groups across session boundaries (which can never be the case
// in fish, anywhere) or to change the process group ID of a session leader (again,
// can never be the case). I'm pretty sure this is a WSL bug, as we see the same
// with tcsetpgrp(2) in other places and it disappears on retry.
debug_safe(2, "setpgid(2) returned EPERM. Retrying");
continue;
} else if (errno == EINTR) {
// I don't think signals are blocked here. The parent (fish) redirected the signal
// handlers and `setup_child_process()` calls `signal_reset_handlers()` after we're
// done here (and not `signal_unblock()`). We're already in a loop, so let's just
// handle EINTR just in case.
continue;
}
}
char pid_buff[128];
char job_id_buff[128];
char getpgid_buff[128];
@ -88,14 +107,15 @@ bool child_set_group(job_t *j, process_t *p) {
pid_buff, argv0, job_id_buff, command, getpgid_buff, job_pgid_buff);
safe_perror("setpgid");
retval = false;
return false;
}
} else {
// The child does not actualyl use this field.
// The child does not actually use this field.
j->pgid = getpgrp();
}
return retval;
return true;
}
/// Called only by the parent only after a child forks and successfully calls child_set_group,