ash: do not set a signal to SIG_DFL if it already is

function                                             old     new   delta
setsignal                                            312     338     +26

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

1 files changed, 7 insertions, 1 deletions

diff --git a/shell/ash.c b/shell/ash.c
index e80425f5e..e8f3ed26b 100644
--- a/shell/ash.c
+++ b/shell/ash.c
@@ -366,7 +366,7 @@ struct globals_misc {
 #define S_DFL      1            /* default signal handling (SIG_DFL) */
 #define S_CATCH    2            /* signal is caught */
 #define S_IGN      3            /* signal is ignored (SIG_IGN) */
-#define S_HARD_IGN 4            /* signal is ignored permanently */
+#define S_HARD_IGN 4            /* signal is ignored permanently (it was SIG_IGN on entry to shell) */
 
         /* indicates specified signal received */
         uint8_t gotsig[NSIG - 1]; /* offset by 1: "signal" 0 is meaningless */
@@ -3566,6 +3566,12 @@ setsignal(int signo)
                                 cur_act = S_IGN;   /* don't hard ignore these */
                         }
                 }
+                if (act.sa_handler == SIG_DFL && new_act == S_DFL) {
+                        /* installing SIG_DFL over SIG_DFL is a no-op */
+                        /* saves one sigaction call in each "sh -c SCRIPT" invocation */
+                        *t = S_DFL;
+                        return;
+                }
         }
         if (cur_act == S_HARD_IGN || cur_act == new_act)
                 return;