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Fix HUP detection on macOS

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As of macOS 15.4, passing 0 or POLLHUP doesn't seem to work at all for
sockets any more (though it does work for `notifyPipe`). As a
workaround, also pass POLLIN. That does cause us to receive a bunch of
POLLIN events we don't care about, so we sleep for a bit when receiving
POLLIN.
This commit is contained in:
Eelco Dolstra 2025-08-27 19:28:04 +02:00
parent 79211b6110
commit 4816b640a2
1 changed files with 14 additions and 1 deletions
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15
src/libutil/unix/include/nix/util/monitor-fd.hh
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@ -55,9 +55,16 @@ public:
// https://github.com/apple-oss-distributions/xnu/commit/e13b1fa57645afc8a7b2e7d868fe9845c6b08c40#diff-a5aa0b0e7f4d866ca417f60702689fc797e9cdfe33b601b05ccf43086c35d395R1468
// That means added in 2007 or earlier. Should be good enough
// for us.
//
// Update: as of macOS 15.4, passing 0 or POLLHUP
// doesn't seem to work at all for sockets any more
// (though it does work for `notifyPipe`). As a
// workaround, also pass POLLIN. That does cause us to
// receive a bunch of POLLIN events we don't care
// about, so we sleep for a bit when receiving POLLIN.
short hangup_events =
#ifdef __APPLE__
POLLHUP
POLLIN | POLLHUP
#else
0
#endif
@ -98,6 +105,12 @@ public:
if (fds[1].revents & POLLHUP) {
break;
}
if (fds[0].revents & POLLIN) {
/* macOS only: we have to pass POLLIN to receive
POLLHUP, but we don't care about POLLIN. To
avoid a lot of wakeups, sleep for a bit. */
std::this_thread::sleep_for(std::chrono::milliseconds(100));
}
// On macOS, (jade thinks that) it is possible (although not
// observed on macOS 14.5) that in some limited cases on buggy
// kernel versions, all the non-POLLHUP events for the socket