We don't really care if the process has a custom handler installed, we
can just set it to default.
The one we check is SIGHUP, which may be given to us via `nohup`.
This saves ~30 syscalls *per process* we spawn, so:
```fish
for f in (seq 1000)
command true
end
```
has ~30000 fewer rt_sigaction calls. These take up about ~30% of the
total time spent in syscalls according to strace.
We could also compute this set once at startup and then reuse it.
If we end up using this in more places, we can create a `Pid` newtype.
Note that while the constant is no longer used in code, its previous value of -2
is still printed by `jobs` when no pgid is associated with a job. I will open a
PR to change this to something else, likely either `0` or `-`.
As of rust 1.78, the Unix stdlib implementation is affected by the same issue:
pub fn sleep(dur: Duration) {
let mut secs = dur.as_secs();
let mut nsecs = dur.subsec_nanos() as _;
// If we're awoken with a signal then the return value will be -1 and
// nanosleep will fill in `ts` with the remaining time.
unsafe {
while secs > 0 || nsecs > 0 {
let mut ts = libc::timespec {
tv_sec: cmp::min(libc::time_t::MAX as u64, secs) as libc::time_t,
tv_nsec: nsecs,
};
secs -= ts.tv_sec as u64;
let ts_ptr = core::ptr::addr_of_mut!(ts);
if libc::nanosleep(ts_ptr, ts_ptr) == -1 {
assert_eq!(os::errno(), libc::EINTR);
secs += ts.tv_sec as u64;
nsecs = ts.tv_nsec;
} else {
nsecs = 0;
}
}
}
}
Note that there is a small behavior change here -- sleep() will continue
after signals; I'm not sure if we want that but it seems harmless?
Part of #10634
