Conditionally unblock after signal handler[#82040]

Only unblock signal after a safe-signal handler is executed if that signal was
also unblocked before the handler.

diff --git a/mg.c b/mg.c
index efc4d6e..f51cd47 100644 (file)
--- a/mg.c
+++ b/mg.c
@@ -1443,15 +1443,32 @@ Perl_despatch_signals(pTHX)
     for (sig = 1; sig < SIG_SIZE; sig++) {
        if (PL_psig_pend[sig]) {
            dSAVE_ERRNO;
-           PERL_BLOCKSIG_ADD(set, sig);
+#if defined(HAS_SIGPROCMASK)
+           /* From sigaction(2) (FreeBSD man page):
+            * | Signal routines normally execute with the signal that
+            * | caused their invocation blocked, but other signals may
+            * | yet occur.
+            * Emulation of this behavior (from within Perl) is enabled
+            * using sigprocmask
+            */
+           int was_blocked;
+           sigset_t newset, oldset;
+
+           sigemptyset(&newset);
+           sigaddset(&newset, sig);
+           sigprocmask(SIG_BLOCK, &newset, &oldset);
+           was_blocked = sigismember(&oldset, sig);
+#endif
            PL_psig_pend[sig] = 0;
-           PERL_BLOCKSIG_BLOCK(set);
 #if defined(HAS_SIGACTION) && defined(SA_SIGINFO)
            (*PL_sighandlerp)(sig, NULL, NULL);
 #else
            (*PL_sighandlerp)(sig);
 #endif
-           PERL_BLOCKSIG_UNBLOCK(set);
+#if defined(HAS_SIGPROCMASK)
+           if (!was_blocked)
+               sigprocmask(SIG_UNBLOCK, &newset, NULL);
+#endif
            RESTORE_ERRNO;
        }
     }