Merge pull request #17155 from opensourcerouting/memstats-zlog

lib: `debug memstats-at-exit` improvements

1 files changed, 12 insertions, 2 deletions

diff --git a/lib/sigevent.c b/lib/sigevent.c
index 3e69f280da..7c465bfcec 100644
--- a/lib/sigevent.c
+++ b/lib/sigevent.c
@@ -237,8 +237,18 @@ core_handler(int signo, siginfo_t *siginfo, void *context)
 
 	zlog_signal(signo, "aborting...", siginfo, pc);
 
-	/* dump memory stats on core */
-	log_memstats(stderr, "core_handler");
+	/* there used to be a log_memstats() call here, to dump MTYPE counters
+	 * on a coredump.  This is not possible since log_memstats is not
+	 * AS-Safe, as it calls fopen(), fprintf(), and cousins.  This can
+	 * lead to a deadlock depending on where we crashed - very much not a
+	 * good thing if the process just hangs there after a crash.
+	 *
+	 * The alarm(1) above tries to alleviate this, but that's really a
+	 * last resort recovery.  Stick with AS-safe calls here.
+	 *
+	 * If the fprintf() calls are removed from log_memstats(), this can be
+	 * added back in, since writing to log with zlog_sigsafe() is AS-safe.
+	 */
 
 	/*
 	 * This is a buffer flush because FRR is going down