Merge pull request #18354 from JuliaLang/yyc/signals/dbg

Make `Ctrl-C` in the debugger works again.

src/signal-handling.c

@@ -53,12 +53,32 @@ static int jl_check_force_sigint(void)
     return 0;
 }
 
-// Force sigint requires pressing `Ctrl-C` repeatedly.
-// Ignore sigint for a short time after that to avoid rethrowing sigint too
-// quickly again. (Code that has this issue is inherently racy but this is
-// an interactive feature anyway.)
+#ifndef _OS_WINDOWS_
+// Not thread local, should only be accessed by the signal handler thread.
+static volatile int jl_sigint_passed = 0;
+static sigset_t jl_sigint_sset;
+#endif
+
 static int jl_ignore_sigint(void)
 {
+    // On Unix, we get the SIGINT before the debugger which makes it very
+    // hard to interrupt a running process in the debugger with `Ctrl-C`.
+    // Manually raise a `SIGINT` on current thread with the signal temporarily
+    // unblocked and use it's behavior to decide if we need to handle the signal.
+#ifndef _OS_WINDOWS_
+    jl_sigint_passed = 0;
+    pthread_sigmask(SIG_UNBLOCK, &jl_sigint_sset, NULL);
+    // This can swallow an external `SIGINT` but it's not an issue
+    // since we don't deliver the same number of signals anyway.
+    pthread_kill(pthread_self(), SIGINT);
+    pthread_sigmask(SIG_BLOCK, &jl_sigint_sset, NULL);
+    if (!jl_sigint_passed)
+        return 1;
+#endif
+    // Force sigint requires pressing `Ctrl-C` repeatedly.
+    // Ignore sigint for a short time after that to avoid rethrowing sigint too
+    // quickly again. (Code that has this issue is inherently racy but this is
+    // an interactive feature anyway.)
     return jl_disable_sigint_time && jl_disable_sigint_time > uv_hrtime();
 }
 

src/signals-unix.c

@@ -519,12 +519,14 @@ static void *signal_listener(void *arg)
 #  endif
 #endif
         if (sig == SIGINT) {
-            if (exit_on_sigint) {
+            if (jl_ignore_sigint()) {
+                continue;
+            }
+            else if (exit_on_sigint) {
                 critical = 1;
             }
             else {
-                if (!jl_ignore_sigint())
-                    jl_try_deliver_sigint();
+                jl_try_deliver_sigint();
                 continue;
             }
         }
@@ -600,6 +602,9 @@ static void *signal_listener(void *arg)
 
 void restore_signals(void)
 {
+    sigemptyset(&jl_sigint_sset);
+    sigaddset(&jl_sigint_sset, SIGINT);
+
     sigset_t sset;
     jl_sigsetset(&sset);
     sigprocmask(SIG_SETMASK, &sset, 0);
@@ -625,6 +630,11 @@ void fpe_handler(int sig, siginfo_t *info, void *context)
     jl_throw_in_ctx(ptls, jl_diverror_exception, context);
 }
 
+void sigint_handler(int sig)
+{
+    jl_sigint_passed = 1;
+}
+
 void jl_install_default_signal_handlers(void)
 {
     struct sigaction actf;
@@ -635,6 +645,14 @@ void jl_install_default_signal_handlers(void)
     if (sigaction(SIGFPE, &actf, NULL) < 0) {
         jl_errorf("fatal error: sigaction: %s", strerror(errno));
     }
+    struct sigaction actint;
+    memset(&actint, 0, sizeof(struct sigaction));
+    sigemptyset(&actint.sa_mask);
+    actint.sa_handler = sigint_handler;
+    actint.sa_flags = 0;
+    if (sigaction(SIGINT, &actint, NULL) < 0) {
+        jl_errorf("fatal error: sigaction: %s", strerror(errno));
+    }
     if (signal(SIGPIPE, SIG_IGN) == SIG_ERR) {
         jl_error("fatal error: Couldn't set SIGPIPE");
     }

src/signals-win.c

@@ -79,10 +79,11 @@ void __cdecl crt_sig_handler(int sig, int num)
         break;
     case SIGINT:
         signal(SIGINT, (void (__cdecl *)(int))crt_sig_handler);
-        if (exit_on_sigint)
-            jl_exit(130); // 128 + SIGINT
-        if (!jl_ignore_sigint())
+        if (!jl_ignore_sigint()) {
+            if (exit_on_sigint)
+                jl_exit(130); // 128 + SIGINT
             jl_try_throw_sigint();
+        }
         break;
     default: // SIGSEGV, (SSIGTERM, IGILL)
         memset(&Context, 0, sizeof(Context));
@@ -179,10 +180,11 @@ static BOOL WINAPI sigint_handler(DWORD wsig) //This needs winapi types to guara
         // etc.
         default: sig = SIGTERM; break;
     }
-    if (exit_on_sigint)
-        jl_exit(128 + sig); // 128 + SIGINT
-    if (!jl_ignore_sigint())
+    if (!jl_ignore_sigint()) {
+        if (exit_on_sigint)
+            jl_exit(128 + sig); // 128 + SIGINT
         jl_try_deliver_sigint();
+    }
     return 1;
 }