Fix linux issues with epoll on normal files.

We use the selfpipe trick if epoll fails with EPERM when trying to
register a file descriptor.

src/core/ev.c

@@ -1082,6 +1082,23 @@ static int make_epoll_events(int mask) {
     return events;
 }
 
+static void janet_epoll_sync_callback(JanetEVGenericMessage msg) {
+    JanetListenerState *state = msg.argp;
+    JanetAsyncStatus status1 = JANET_ASYNC_STATUS_NOT_DONE;
+    JanetAsyncStatus status2 = JANET_ASYNC_STATUS_NOT_DONE;
+    if (state->stream->_mask & JANET_ASYNC_LISTEN_WRITE)
+        status1 = state->machine(state, JANET_ASYNC_EVENT_WRITE);
+    if (state->stream->_mask & JANET_ASYNC_LISTEN_WRITE)
+        status2 = state->machine(state, JANET_ASYNC_EVENT_READ);
+    if (status1 == JANET_ASYNC_STATUS_DONE ||
+            status2 == JANET_ASYNC_STATUS_DONE) {
+        janet_unlisten(state, 0);
+    } else {
+        /* Repost event */
+        janet_ev_post_event(NULL, janet_epoll_sync_callback, msg);
+    }
+}
+
 /* Wait for the next event */
 JanetListenerState *janet_listen(JanetStream *stream, JanetListener behavior, int mask, size_t size, void *user) {
     int is_first = !(stream->state);
@@ -1095,9 +1112,23 @@ JanetListenerState *janet_listen(JanetStream *stream, JanetListener behavior, in
         status = epoll_ctl(janet_vm.epoll, op, stream->handle, &ev);
     } while (status == -1 && errno == EINTR);
     if (status == -1) {
+        if (errno == EPERM) {
+            /* Couldn't add to event loop, so assume that it completes
+             * synchronously. In that case, fire the completion
+             * event manually, since this should be a read or write
+             * event to a file. So we just post a custom event to do the read/write
+             * asap. */
+            /* Use flag to indicate state is not registered in epoll */
+            state->_mask |= (1 << JANET_ASYNC_EVENT_COMPLETE);
+            JanetEVGenericMessage msg = {0};
+            msg.argp = state;
+            janet_ev_post_event(NULL, janet_epoll_sync_callback, msg);
+        } else {
+            /* Unexpected error */
             janet_unlisten_impl(state, 0);
             janet_panicv(janet_ev_lasterr());
         }
+    }
     return state;
 }
 
@@ -1105,6 +1136,8 @@ JanetListenerState *janet_listen(JanetStream *stream, JanetListener behavior, in
 static void janet_unlisten(JanetListenerState *state, int is_gc) {
     JanetStream *stream = state->stream;
     if (!(stream->flags & JANET_STREAM_CLOSED)) {
+        /* Use flag to indicate state is not registered in epoll */
+        if (!(state->_mask & (1 << JANET_ASYNC_EVENT_COMPLETE))) {
             int is_last = (state->_next == NULL && stream->state == state);
             int op = is_last ? EPOLL_CTL_DEL : EPOLL_CTL_MOD;
             struct epoll_event ev;
@@ -1118,6 +1151,7 @@ static void janet_unlisten(JanetListenerState *state, int is_gc) {
                 janet_panicv(janet_ev_lasterr());
             }
         }
+    }
     /* Destroy state machine and free memory */
     janet_unlisten_impl(state, is_gc);
 }
@@ -1358,7 +1392,7 @@ void janet_ev_post_event(JanetVM *vm, JanetCallback cb, JanetEVGenericMessage ms
     JanetSelfPipeEvent event;
     event.msg = msg;
     event.cb = cb;
-    int fd = vm->selfpipe;
+    int fd = vm->selfpipe[1];
     /* handle a bit of back pressure before giving up. */
     int tries = 4;
     while (tries > 0) {

src/core/util.c

@@ -553,7 +553,8 @@ void janet_core_cfuns(JanetTable *env, const char *regprefix, const JanetReg *cf
 }
 
 void janet_core_def_sm(JanetTable *env, const char *name, Janet x, const void *p, const void *sf, int32_t sl) {
-    (void) sf, sl;
+    (void) sf;
+    (void) sl;
     janet_core_def(env, name, x, p);
 }