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Only use clone3 when needed for pidfd #89924

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Merged
merged 3 commits into from
Oct 16, 2021
Merged

Only use clone3 when needed for pidfd #89924

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de2e483
Only use `clone3` when needed for pidfd
cuviper Oct 15, 2021
ad6e5e1
Update another comment on fork vs. clone3
cuviper Oct 15, 2021
74ef530
Also note tool expectations of fork vs clone3
cuviper Oct 15, 2021
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6 changes: 5 additions & 1 deletion library/std/src/sys/unix/process/process_unix.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -166,14 +166,18 @@ impl Command {
fn clone3(cl_args: *mut clone_args, len: libc::size_t) -> libc::c_long
}

// Bypassing libc for `clone3` can make further libc calls unsafe,
// so we use it sparingly for now. See #89522 for details.
let want_clone3 = self.get_create_pidfd();

// If we fail to create a pidfd for any reason, this will
// stay as -1, which indicates an error.
let mut pidfd: pid_t = -1;

// Attempt to use the `clone3` syscall, which supports more arguments
// (in particular, the ability to create a pidfd). If this fails,
// we will fall through this block to a call to `fork()`
if HAS_CLONE3.load(Ordering::Relaxed) {
if want_clone3 && HAS_CLONE3.load(Ordering::Relaxed) {
let mut flags = 0;
if self.get_create_pidfd() {
flags |= CLONE_PIDFD;
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