[git commit] init: reduce the window when init can lose reboot/poweroff signals

Denys Vlasenko vda.linux at googlemail.com
Thu Nov 2 14:25:28 UTC 2017


commit: https://git.busybox.net/busybox/commit/?id=f5e8b4278822f2413bf7e47466f55cc1a0fcca9a
branch: https://git.busybox.net/busybox/commit/?id=refs/heads/master

function                                             old     new   delta
init_main                                            695     712     +17

Signed-off-by: Denys Vlasenko <vda.linux at googlemail.com>
---
 init/init.c | 31 ++++++++-----------------------
 1 file changed, 8 insertions(+), 23 deletions(-)

diff --git a/init/init.c b/init/init.c
index 5304e5c..6f3374e 100644
--- a/init/init.c
+++ b/init/init.c
@@ -1064,6 +1064,12 @@ int init_main(int argc UNUSED_PARAM, char **argv)
 #endif
 
 	if (!DEBUG_INIT) {
+		/* Some users send poweroff signals to init VERY early.
+		 * To handle this, mask signals early,
+		 * and unmask them only after signal handlers are installed.
+		 */
+		sigprocmask_allsigs(SIG_BLOCK);
+
 		/* Expect to be invoked as init with PID=1 or be invoked as linuxrc */
 		if (getpid() != 1
 		 && (!ENABLE_LINUXRC || applet_name[0] != 'l') /* not linuxrc? */
@@ -1106,29 +1112,6 @@ int init_main(int argc UNUSED_PARAM, char **argv)
 	message(L_CONSOLE | L_LOG, "init started: %s", bb_banner);
 #endif
 
-#if 0
-/* It's 2013, does anyone really still depend on this? */
-/* If you do, consider adding swapon to sysinit actions then! */
-/* struct sysinfo is linux-specific */
-# ifdef __linux__
-	/* Make sure there is enough memory to do something useful. */
-	/*if (ENABLE_SWAPONOFF) - WRONG: we may have non-bbox swapon*/ {
-		struct sysinfo info;
-
-		if (sysinfo(&info) == 0
-		 && (info.mem_unit ? info.mem_unit : 1) * (long long)info.totalram < 1024*1024
-		) {
-			message(L_CONSOLE, "Low memory, forcing swapon");
-			/* swapon -a requires /proc typically */
-			new_init_action(SYSINIT, "mount -t proc proc /proc", "");
-			/* Try to turn on swap */
-			new_init_action(SYSINIT, "swapon -a", "");
-			run_actions(SYSINIT);   /* wait and removing */
-		}
-	}
-# endif
-#endif
-
 	/* Check if we are supposed to be in single user mode */
 	if (argv[1]
 	 && (strcmp(argv[1], "single") == 0 || strcmp(argv[1], "-s") == 0 || LONE_CHAR(argv[1], '1'))
@@ -1204,6 +1187,8 @@ int init_main(int argc UNUSED_PARAM, char **argv)
 			+ (1 << SIGHUP)  /* reread /etc/inittab */
 #endif
 			, record_signo);
+
+		sigprocmask_allsigs(SIG_UNBLOCK);
 	}
 
 	/* Now run everything that needs to be run */


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