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fix: prerm kill sweep must not kill its own ancestors

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`ps | grep '/usr/bin/tachyon'` matches the hook itself, because
/usr/bin/tachyon is what invoked it. The sweep therefore killed its own
parent, the parent died on SIGKILL, and apk saw
`tachyon-<version>.pre-upgrade: exited with error 247` (128+119) and
reported a failed hook.

The sweep now walks /proc/<pid>/stat to collect its own ancestor chain and
skips those pids.

Holders of procd's serialization lock are also cleared by descriptor rather
than by name. procd_lock() does `exec 1000>` on
/var/lock/procd_tachyon.lock and then `flock 1000` with no -w, so any
background spawn inheriting fd 1000 keeps the lock held. On a live router
the holders were watchdog workers, logread, the zapret2 supervisors, nfqws2
and a stray curl — none of which match a tachyon name pattern. While any of
them lives, every init.d call blocks in flock until the package manager
gives up on the hook.

Same descriptor-based sweep added to install.sh, which faces the same lock
left behind by pre-fix builds.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
This commit is contained in:
Dushnilin
2026-08-09 20:50:08 +03:00
co-authored by Claude Opus 5
parent 547f42e92d
commit 4ce5d7ebac
4 changed files with 108 additions and 6 deletions
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tachyon/files/usr/lib/service/package.uc
+34 -6
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@@ -100,6 +100,23 @@ function bounded_command_success_from_args(args, seconds) {
return command_success_from_args(bounded);
}
// A kill sweep must not take out the process running it. `ps | grep '/usr/bin/tachyon'`
// matches this very hook — /usr/bin/tachyon is what invoked it — so the naive sweep
// killed its own parent; the parent died on SIGKILL, and apk saw the pre-upgrade hook
// exit 247 (128+119) and reported a failed hook. The ancestor chain of the shell doing
// the sweep is walked out of /proc and skipped. Field 2 after the ")" of /proc/<pid>/stat
// is the ppid; the comm field is stripped first because it may itself contain spaces.
function kill_matching_command(grep_args) {
return "__anc=\" \"; __p=$$; " +
"while [ -n \"$__p\" ] && [ \"$__p\" -gt 1 ] 2>/dev/null; do " +
"__anc=\"$__anc$__p \"; " +
"__p=$(awk '{ sub(/.*\\) /, \"\"); print $2 }' \"/proc/$__p/stat\" 2>/dev/null); " +
"done; " +
"ps 2>/dev/null | grep " + grep_args + " | grep -v grep | awk '{print $1}' | " +
"while read _pid; do case \"$__anc\" in *\" $_pid \"*) continue;; esac; " +
"kill -9 \"$_pid\" 2>/dev/null; done; true";
}
function path_exists(path) {
return fs.stat(as_string(path)) != null;
}
@@ -186,8 +203,19 @@ function prerm_cleanup(action) {
// to prevent INIT_PATH stop from blocking indefinitely on rc.common flock -w 1000.
// This has to happen before the status probe below, or that probe becomes the
// very thing that waits on the lock those processes hold.
system("ps 2>/dev/null | grep -E '99-tachyon-wan|flock 1000|init[.]d/tachyon' | awk '{print $1}' | while read _pid; do kill -9 \"$_pid\" 2>/dev/null; done; true");
system("ps 2>/dev/null | grep -F '/etc/init.d/tachyon' | awk '{print $1}' | while read _pid; do kill -9 \"$_pid\" 2>/dev/null; done; true");
system(kill_matching_command("-E '99-tachyon-wan|flock 1000|init[.]d/tachyon'"));
system(kill_matching_command("-F '/etc/init.d/tachyon'"));
// procd leaks its serialization lock: procd_lock() does `exec 1000>` on
// /var/lock/procd_tachyon.lock and then `flock 1000` with no -w, so every
// background spawn that inherits fd 1000 keeps the lock held after the init
// script exits. Builds before this fix swept /proc/self/fd only up to 999 and
// missed exactly that descriptor. The holders may therefore be pre-fix
// processes with no other reason to die, so they are cleared by descriptor
// rather than by name — otherwise INIT_PATH below blocks forever.
system("for __f in /proc/[0-9]*; do [ -e \"$__f/fd/1000\" ] || continue; " +
"case \"$(readlink \"$__f/fd/1000\" 2>/dev/null)\" in *procd_tachyon*) " +
"__pid=${__f##*/}; [ \"$__pid\" = \"$$\" ] || kill -9 \"$__pid\" 2>/dev/null;; " +
"esac; done; true");
}
remember_upgrade_state(action);
@@ -196,8 +224,8 @@ function prerm_cleanup(action) {
bounded_command_success_from_args([BIN_PATH, "stop"]);
bounded_command_success_from_args([INIT_PATH, "stop"]);
// Kill any remaining tachyon processes
system("ps 2>/dev/null | grep -F '/usr/bin/tachyon' | awk '{print $1}' | while read _pid; do kill -9 \"$_pid\" 2>/dev/null; done; true");
// Kill any remaining tachyon processes, minus this hook's own ancestors.
system(kill_matching_command("-F '" + BIN_PATH + "'"));
restore_dnsmasq_if_needed();
remove_managed_sing_box();
}
@@ -211,8 +239,8 @@ function postinst_restore() {
if (!PACKAGE_TEST_MODE) {
// Kill any flock waiters and init.d/tachyon processes that appeared since prerm ran.
system("ps 2>/dev/null | grep -E '99-tachyon-wan|flock 1000' | awk '{print $1}' | while read _pid; do kill -9 \"$_pid\" 2>/dev/null; done; true");
system("ps 2>/dev/null | grep -F '/etc/init.d/tachyon' | awk '{print $1}' | while read _pid; do kill -9 \"$_pid\" 2>/dev/null; done; true");
system(kill_matching_command("-E '99-tachyon-wan|flock 1000'"));
system(kill_matching_command("-F '/etc/init.d/tachyon'"));
}
// Start via INIT_PATH. Bounded: a start that hangs must not take the package
// transaction down with it — the service can be started by hand afterwards,