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lightingd: removal of sigchild_handler in shutdown now also closes its pipe

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Setting SIGCHLD back to default (i.e. ignored) makes waitpid hang on an
old SIGCHLD that was still in the pipe?

This happens running test_important_plugin with developer=1:
(or with dev=0 and build-in plugins subscribed to "shutdown")

0  0x00007ff8336b6437 in __GI___waitpid (pid=-1, stat_loc=0x0, options=1) at ../sysdeps/unix/sysv/linux/waitpid.c:30
1  0x000055fb468f733a in sigchld_rfd_in (conn=0x55fb47c7cfc8, ld=0x55fb47bdce58) at lightningd/lightningd.c:785
2  0x000055fb469bcc6b in next_plan (conn=0x55fb47c7cfc8, plan=0x55fb47c7cfe8) at ccan/ccan/io/io.c:59
3  0x000055fb469bd80b in do_plan (conn=0x55fb47c7cfc8, plan=0x55fb47c7cfe8, idle_on_epipe=false) at ccan/ccan/io/io.c:407
4  0x000055fb469bd849 in io_ready (conn=0x55fb47c7cfc8, pollflags=1) at ccan/ccan/io/io.c:417
5  0x000055fb469bfa26 in io_loop (timers=0x55fb47c41198, expired=0x7ffdf4be9028) at ccan/ccan/io/poll.c:453
6  0x000055fb468f1be9 in io_loop_with_timers (ld=0x55fb47bdce58) at lightningd/io_loop_with_timers.c:21
7  0x000055fb46924817 in shutdown_plugins (ld=0x55fb47bdce58) at lightningd/plugin.c:2114
8  0x000055fb468f7c92 in main (argc=22, argv=0x7ffdf4be9228) at lightningd/lightningd.c:1195
This commit is contained in:
Simon Vrouwe 2021-11-08 18:19:20 +02:00 • committed by Rusty Russell
parent e08528b7b5
commit ae4623c21a
1 changed files with 6 additions and 6 deletions
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12
lightningd/lightningd.c
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@ -757,13 +757,14 @@ static int setup_sig_handlers(void)
/*~ This removes the SIGCHLD handler, so we don't try to write
* to a broken pipe. */
static void remove_sigchild_handler(void)
static void remove_sigchild_handler(struct io_conn *sigchld_conn)
{
struct sigaction sigchild;
memset(&sigchild, 0, sizeof(struct sigaction));
sigchild.sa_handler = SIG_DFL;
sigaction(SIGCHLD, &sigchild, NULL);
io_close(sigchld_conn);
}
/*~ This is the routine which sets up the sigchild handling. We just
@ -854,6 +855,7 @@ int main(int argc, char *argv[])
struct htlc_in_map *unconnected_htlcs_in;
struct ext_key *bip32_base;
int sigchld_rfd;
struct io_conn *sigchld_conn;
int exit_code = 0;
char **orig_argv;
bool try_reexec;
@ -1099,10 +1101,8 @@ int main(int argc, char *argv[])
* "funding transaction spent" event which creates it. */
onchaind_replay_channels(ld);
/*~ Now handle sigchld, so we can clean up appropriately.
* We don't keep a pointer to this, so our simple leak detection
* code gets upset unless we mark it notleak(). */
notleak(io_new_conn(ld, sigchld_rfd, sigchld_rfd_in, ld));
/*~ Now handle sigchld, so we can clean up appropriately. */
sigchld_conn = notleak(io_new_conn(ld, sigchld_rfd, sigchld_rfd_in, ld));
/*~ Mark ourselves live.
*
@ -1189,7 +1189,7 @@ int main(int argc, char *argv[])
stop_topology(ld->topology);
/* We're not going to collect our children. */
remove_sigchild_handler();
remove_sigchild_handler(sigchld_conn);
shutdown_subdaemons(ld);
/* Tell plugins we're shutting down, closes the db for write access. */