Add support for sigqueue() and also handle SIGUSR2

I anticipate using sigqueue() for simpler handling of SIGCHLD
notifications from the prewram process to the its parent.

kitty/child-monitor.c

@@ -23,6 +23,10 @@
 #include <signal.h>
 extern PyTypeObject Screen_Type;
 
+#if defined(__APPLE__) || defined(__OpenBSD__)
+#define NO_SIGQUEUE 1
+#endif
+
 #ifdef DEBUG_EVENT_LOOP
 #define EVDBG(...) log_event(__VA_ARGS__)
 #else
@@ -801,11 +805,25 @@ free_twd(ThreadWriteData *x) {
     free(x);
 }
 
+static PyObject*
+sig_queue(PyObject *self UNUSED, PyObject *args) {
+    int pid, signal, value;
+    if (!PyArg_ParseTuple(args, "iii", &pid, &signal, &value)) return NULL;
+#ifdef NO_SIGQUEUE
+    if (kill(pid, signal) != 0) { PyErr_SetFromErrno(PyExc_OSError); return NULL; }
+#else
+    union sigval v;
+    v.sival_int = value;
+    if (sigqueue(pid, signal, v) != 0) { PyErr_SetFromErrno(PyExc_OSError); return NULL; }
+#endif
+    Py_RETURN_NONE;
+}
+
 static PyObject*
 monitor_pid(PyObject *self UNUSED, PyObject *args) {
-    long pid;
+    int pid;
     bool ok = true;
-    if (!PyArg_ParseTuple(args, "l", &pid)) return NULL;
+    if (!PyArg_ParseTuple(args, "i", &pid)) return NULL;
     children_mutex(lock);
     if (monitored_pids_count >= arraysz(monitored_pids)) {
         PyErr_SetString(PyExc_RuntimeError, "Too many monitored pids");
@@ -1224,7 +1242,7 @@ read_bytes(int fd, Screen *screen) {
 typedef struct { bool kill_signal, child_died, reload_config; } SignalSet;
 
 static void
-handle_signal(int signum, void *data) {
+handle_signal(int32_t signum, int32_t sigval, void *data) {
     SignalSet *ss = data;
     switch(signum) {
         case SIGINT:
@@ -1237,6 +1255,9 @@ handle_signal(int signum, void *data) {
         case SIGUSR1:
             ss->reload_config = true;
             break;
+        case SIGUSR2:
+            printf("Received SIGUSR2: %d\n", sigval);
+            break;
         default:
             break;
     }
@@ -1739,6 +1760,7 @@ static PyMethodDef module_methods[] = {
     METHODB(monitor_pid, METH_VARARGS),
     METHODB(send_data_to_peer, METH_VARARGS),
     METHODB(cocoa_set_menubar_title, METH_VARARGS),
+    {"sigqueue", (PyCFunction)sig_queue, METH_VARARGS, ""},
     {NULL}  /* Sentinel */
 };
 
@@ -1748,6 +1770,11 @@ init_child_monitor(PyObject *module) {
     if (PyModule_AddObject(module, "ChildMonitor", (PyObject *)&ChildMonitor_Type) != 0) return false;
     Py_INCREF(&ChildMonitor_Type);
     if (PyModule_AddFunctions(module, module_methods) != 0) return false;
+#ifdef NO_SIGQUEUE
+    PyModule_AddIntConstant(module, "has_sigqueue", 0);
+#else
+    PyModule_AddIntConstant(module, "has_sigqueue", 1);
+#endif
     return true;
 }
 

kitty/fast_data_types.pyi

@@ -1375,3 +1375,7 @@ def shm_open(name: str, flags: int, mode: int = 0o600) -> int:
 
 def shm_unlink(name: str) -> None:
     pass
+
+
+def sigqueue(pid: int, signal: int, value: int) -> None:
+    pass

kitty/loop-utils.c

@@ -29,11 +29,14 @@ init_loop_data(LoopData *ld) {
 static int signal_write_fd = -1;
 
 static void
-handle_signal(int sig_num) {
+handle_signal(int sig_num, siginfo_t *si, void *ucontext UNUSED) {
     int save_err = errno;
-    unsigned char byte = (unsigned char)sig_num;
-    while(signal_write_fd != -1) {
-        ssize_t ret = write(signal_write_fd, &byte, 1);
+    char buf[8];
+    int32_t sigval = si->si_value.sival_int, signum = sig_num;
+    memcpy(buf, &signum, 4);
+    memcpy(buf + 4, &sigval, 4);
+    while (signal_write_fd != -1) {
+        ssize_t ret = write(signal_write_fd, buf, 8);
         if (ret < 0 && errno == EINTR) continue;
         break;
     }
@@ -45,7 +48,7 @@ handle_signal(int sig_num) {
 #define SIGNAL_SET \
     sigset_t signals = {0}; \
     sigemptyset(&signals); \
-    sigaddset(&signals, SIGINT); sigaddset(&signals, SIGTERM); sigaddset(&signals, SIGCHLD); sigaddset(&signals, SIGUSR1); \
+    sigaddset(&signals, SIGINT); sigaddset(&signals, SIGTERM); sigaddset(&signals, SIGCHLD); sigaddset(&signals, SIGUSR1); sigaddset(&signals, SIGUSR2); \
 
 void
 free_loop_data(LoopData *ld) {
@@ -68,6 +71,8 @@ free_loop_data(LoopData *ld) {
         signal(SIGINT, SIG_DFL);
         signal(SIGTERM, SIG_DFL);
         signal(SIGCHLD, SIG_DFL);
+        signal(SIGUSR1, SIG_DFL);
+        signal(SIGUSR2, SIG_DFL);
     }
 #ifdef HAS_EVENT_FD
     safe_close(ld->wakeup_read_fd, __FILE__, __LINE__);
@@ -104,9 +109,9 @@ install_signal_handlers(LoopData *ld) {
 #else
     if (!self_pipe(ld->signal_fds, true)) return false;
     signal_write_fd = ld->signal_fds[1];
-    struct sigaction act = {.sa_handler=handle_signal};
+    struct sigaction act = {.sa_sigaction=handle_signal, .sa_flags=SA_SIGINFO};
 #define SA(which) { if (sigaction(which, &act, NULL) != 0) return false; if (siginterrupt(which, false) != 0) return false; }
-    SA(SIGINT); SA(SIGTERM); SA(SIGCHLD); SA(SIGUSR1);
+    SA(SIGINT); SA(SIGTERM); SA(SIGCHLD); SA(SIGUSR1); SA(SIGUSR2);
 #undef SA
     ld->signal_read_fd = ld->signal_fds[0];
 #endif
@@ -132,18 +137,25 @@ read_signals(int fd, handle_signal_func callback, void *data) {
             log_error("Incomplete signal read from signalfd");
             break;
         }
-        for (size_t i = 0; i < num_signals; i++) callback(fdsi[i].ssi_signo, data);
+        for (size_t i = 0; i < num_signals; i++) callback(fdsi[i].ssi_signo, fdsi[i].ssi_int, data);
     }
 #else
     static char buf[256];
+    static size_t buf_pos = 0;
     while(true) {
-        ssize_t len = read(fd, buf, sizeof(buf));
+        ssize_t len = read(fd, buf + buf_pos, sizeof(buf) - buf_pos);
         if (len < 0) {
             if (errno == EINTR) continue;
             if (errno != EIO && errno != EAGAIN) log_error("Call to read() from read_signals() failed with error: %s", strerror(errno));
             break;
         }
-        for (ssize_t i = 0; i < len; i++) callback(buf[i], data);
+        buf_pos += len;
+        while (buf_pos >= 8) {
+            int32_t *sdata = (int32_t*)buf;
+            callback(sdata[0], sdata[1], data);
+            memmove(buf, buf + 8, 8);
+            buf_pos -= 8;
+        }
         if (len == 0) break;
     }
 #endif

kitty/loop-utils.h

@@ -37,7 +37,7 @@ typedef struct {
     int wakeup_read_fd;
     int signal_read_fd;
 } LoopData;
-typedef void(*handle_signal_func)(int, void *data);
+typedef void(*handle_signal_func)(int32_t, int32_t, void *data);
 
 bool init_loop_data(LoopData *ld);
 void free_loop_data(LoopData *ld);