Hi,
When testing version 2.21.0 of git on AIX (6.1 & 7.2), I have found an issue
with daemon.c and test t5570-git-daemon.sh : within test 4, the child_handler()
code gets crazy and calls itself recursively till the process crashes. We do
not have a clear idea why this issue occurs. Maybe that this issue also appears
on other operating systems.
This code:
static void child_handler(int signo)
{
signal(SIGCHLD, child_handler);
}
is the root cause and it appeared in 2008, for SysV :
https://git.kernel.org/pub/scm/git/git.git/commit/daemon.c?id=bd7b371e9c2aeb0aaf228dc1655e8d04fca6f797
I suggest to use the attached patch git-2.21.0-SIGCHLD-handler-v3.patch, so
that this issue on AIX disappears.
Moreover, this code may also be useful for other operating systems. Someone
should tests it on Solaris.
I have checked that this patch is OK (build & test t5570-git-daemon.sh) on
Linux/Power (Fedora 28) with GCC (v8.1).
I've also checked on Linux/Power that the 21 tests of t5570-git-daemon.sh are
OK when one replaces the existing code using:
signal(SIGCHLD, child_handler);
by the code dedicated to AIX.
I mean to say that this sigaction(SIGCHLD, &sa, NULL) code could also replace
on Linux the current potentially-dangerous code based on signal(SIGCHLD,
child_handler).
Regards,
Tony
[email protected]
ATOS / Bull SAS
ATOS Expert
IBM Coop Architect & Technical Leader
Office : +33 (0) 4 76 29 72 67
1 rue de Provence - 38432 Échirolles - France
www.atos.net --- ./daemon.c.ORIGIN 2019-03-18 17:53:51 +0100
+++ ./daemon.c 2019-03-18 18:00:16 +0100
@@ -943,8 +943,11 @@
* Otherwise empty handler because systemcalls will get interrupted
* upon signal receipt
* SysV needs the handler to be rearmed
+ * AIX does NOT like sometimes (t5570-git-daemon test 4) to rearm it.
*/
+#ifndef _AIX
signal(SIGCHLD, child_handler);
+#endif
}
static int set_reuse_addr(int sockfd)
@@ -1155,7 +1158,19 @@
pfd[i].events = POLLIN;
}
+#ifdef _AIX
+ /* AIX does NOT like sometimes (t5570-git-daemon test 4) to rearm the SIGCHLD handler */
+ struct sigaction sa;
+
+ bzero(&sa, sizeof(sa));
+ sa.sa_handler = child_handler;
+ sa.sa_flags = 0;
+ sigemptyset(&sa.sa_mask);
+
+ sigaction(SIGCHLD, &sa, NULL);
+#else
signal(SIGCHLD, child_handler);
+#endif
for (;;) {
int i;
