mgt_main: Preserve VSM after startup panics

bin/varnishd/cache/cache_main.c

@@ -462,6 +462,9 @@ child_main(int sigmagic, size_t altstksz)
 		SMP_Ready();
 #endif
 
+	if (DO_DEBUG(DBG_STARTUP_PANIC))
+		WRONG("startup_panic");
+
 	CLI_Run();
 
 	if (shutdown_delay > 0)

bin/varnishd/mgt/mgt_child.c

@@ -347,7 +347,7 @@ mgt_launch_child(struct cli *cli)
 	if ((pid = fork()) < 0) {
 		VJ_master(JAIL_MASTER_LOW);
 		perror("Could not fork child");
-		exit(1);		// XXX Harsh ?
+		_exit(1);		// XXX Harsh ?
 	}
 	if (pid == 0) {
 

bin/varnishd/mgt/mgt_main.c

@@ -964,7 +964,7 @@ main(int argc, char * const *argv)
 		mgt_eric_im_done(eric_fd, u);
 
 	if (u)
-		exit(u);
+		_exit(u);
 
 	/* Failure is no longer an option */
 

bin/varnishtest/tests/u00020.vtc

@@ -0,0 +1,35 @@
+varnishtest "panic during startup"
+
+varnish v1 -cliok "param.set feature +no_coredump"
+
+# late startup panic
+varnish v1 -vcl {
+	import vtc;
+
+	backend be none;
+
+	sub vcl_init {
+		vtc.panic("vcl_init");
+	}
+}
+
+varnish v1 -clierr 400 start
+varnish v1 -cliexpect vcl_init panic.show
+varnish v1 -cliok panic.clear
+varnish v1 -expectexit 0x40
+
+# early startup panic
+process p1 {
+	exec varnishd -F -n "${tmpdir}/p1/workdir" \
+		-a ${localhost}:0 -b ${localhost}:0 \
+		-p feature=+no_coredump -p debug=+startup_panic
+} -expect-exit 2 -run
+
+# post-mortem inspection
+shell -match "MGT.child_start( +)1" {
+	varnishstat -n "${tmpdir}/p1/workdir" -1
+}
+
+shell -match "MGT.child_panic( +)1" {
+	varnishstat -n "${tmpdir}/p1/workdir" -1
+}

include/tbl/debug_bits.h

@@ -52,6 +52,7 @@ DEBUG_BIT(PROCESSORS,		processors,	"Fetch/Deliver processors")
 DEBUG_BIT(PROTOCOL,		protocol,	"Protocol debugging")
 DEBUG_BIT(VCL_KEEP,		vcl_keep,	"Keep VCL C and so files")
 DEBUG_BIT(LCK,			lck,		"Additional lock statistics")
+DEBUG_BIT(STARTUP_PANIC,	startup_panic,	"Panic early during cache startup")
 #undef DEBUG_BIT
 
 /*lint -restore */