Add ev api for making threaded calls.

Easy way to make arbitrary functions in C async.

examples/async-execute.janet

@@ -1,6 +1,6 @@
 (defn dowork [name n]
   (print name " starting work...")
-  (os/execute ["sleep" (string n)] :p)
+  (os/execute [(dyn :executable) "-e" (string "(os/sleep " n ")")])
   (print name " finished work!"))
 
 # Will be done in parallel

src/core/ev.c

@@ -33,6 +33,7 @@
 
 /* Includes */
 #include <math.h>
+#include <pthread.h>
 #ifdef JANET_WINDOWS
 #include <winsock2.h>
 #include <windows.h>
@@ -883,6 +884,21 @@ void janet_loop(void) {
  * Self-pipe handling code.
  */
 
+/* Structure used to initialize threads in the thread pool. */
+typedef struct {
+    int write_pipe;
+    JanetEVGenericMessage msg;
+    JanetThreadedSubroutine subr;
+    JanetThreadedCallback cb;
+} JanetEVThreadInit;
+
+/* Wrap return value by pairing it with the callback used to handle it
+ * in the main thread */
+typedef struct {
+    JanetEVGenericMessage msg;
+    JanetThreadedCallback cb;
+} JanetSelfPipeEvent;
+
 #ifdef JANET_WINDOWS
 
 #else
@@ -891,15 +907,10 @@ JANET_THREAD_LOCAL int janet_vm_selfpipe[2];
 
 /* Handle events from the self pipe inside the event loop */
 static void janet_ev_handle_selfpipe(void) {
-    JanetSelfPipeEvent ev;
-    while (read(janet_vm_selfpipe[0], &ev, sizeof(ev)) > 0) {
-        switch (ev.tag) {
-            default:
-                break;
-            case JANET_SELFPIPE_PROC:
-                janet_schedule_proc(ev.as.proc.proc, ev.as.proc.status);
-                break;
-        }
+    JanetSelfPipeEvent response;
+    while (read(janet_vm_selfpipe[0], &response, sizeof(response)) > 0) {
+        response.cb(response.msg);
+        janet_ev_dec_refcount();
     }
 }
 
@@ -919,6 +930,97 @@ static void janet_ev_cleanup_selfpipe(void) {
 
 #endif
 
+static void *janet_thread_body(void *ptr) {
+    JanetEVThreadInit *init = (JanetEVThreadInit *)ptr;
+    int fd = init->write_pipe;
+    JanetEVGenericMessage msg = init->msg;
+    JanetThreadedSubroutine subr = init->subr;
+    JanetThreadedCallback cb = init->cb;
+    free(init);
+
+    JanetSelfPipeEvent response;
+    response.msg = subr(msg);
+    response.cb = cb;
+
+    /* TODO - implement for windows */
+    if (write(fd, &response, sizeof(response)) < 0) {
+        /* TODO failed to handle signal. */
+        fprintf(stderr, "failed to write response\n");
+    }
+
+    return NULL;
+}
+
+void janet_ev_threaded_call(JanetThreadedSubroutine fp, JanetEVGenericMessage arguments, JanetThreadedCallback cb) {
+    JanetEVThreadInit *init = malloc(sizeof(JanetEVThreadInit));
+    if (NULL == init) {
+        JANET_OUT_OF_MEMORY;
+    }
+    init->write_pipe = janet_vm_selfpipe[1];
+    init->msg = arguments;
+    init->subr = fp;
+    init->cb = cb;
+
+    /* Create thread - TODO thread pool? */
+    pthread_attr_t attr;
+    pthread_t waiter_thread;
+    pthread_attr_init(&attr);
+    pthread_attr_setstacksize(&attr, PTHREAD_STACK_MIN);
+    int err = pthread_create(&waiter_thread, NULL, janet_thread_body, init);
+    pthread_attr_destroy(&attr);
+    if (err) {
+        free(init);
+        janet_panicf("%s", strerror(err));
+    }
+    pthread_detach(waiter_thread);
+
+    /* Increment ev refcount so we don't quit while waiting for a subprocess */
+    janet_ev_inc_refcount();
+}
+
+/* Default callback for janet_ev_threaded_await. */
+void janet_ev_default_threaded_callback(JanetEVGenericMessage return_value) {
+    switch (return_value.tag) {
+        default:
+        case JANET_EV_TCTAG_NIL:
+            janet_schedule(return_value.fiber, janet_wrap_nil());
+            break;
+        case JANET_EV_TCTAG_INTEGER:
+            janet_schedule(return_value.fiber, janet_wrap_integer(return_value.argi));
+            break;
+        case JANET_EV_TCTAG_STRING:
+        case JANET_EV_TCTAG_STRINGF:
+            janet_schedule(return_value.fiber, janet_cstringv((const char *) return_value.argp));
+            if (return_value.tag == JANET_EV_TCTAG_STRINGF) free(return_value.argp);
+            break;
+        case JANET_EV_TCTAG_KEYWORD:
+            janet_schedule(return_value.fiber, janet_ckeywordv((const char *) return_value.argp));
+            break;
+        case JANET_EV_TCTAG_ERR_STRING:
+        case JANET_EV_TCTAG_ERR_STRINGF:
+            janet_cancel(return_value.fiber, janet_cstringv((const char *) return_value.argp));
+            if (return_value.tag == JANET_EV_TCTAG_STRINGF) free(return_value.argp);
+            break;
+        case JANET_EV_TCTAG_ERR_KEYWORD:
+            janet_cancel(return_value.fiber, janet_ckeywordv((const char *) return_value.argp));
+            break;
+    }
+    janet_gcunroot(janet_wrap_fiber(return_value.fiber));
+}
+
+
+/* Convenience method for common case */
+void janet_ev_threaded_await(JanetThreadedSubroutine fp, int tag, int argi, void *argp) {
+    JanetEVGenericMessage arguments;
+    arguments.tag = tag;
+    arguments.argi = argi;
+    arguments.argp = argp;
+    arguments.fiber = janet_root_fiber();
+    janet_gcroot(janet_wrap_fiber(arguments.fiber));
+    janet_ev_threaded_call(fp, arguments, janet_ev_default_threaded_callback);
+    janet_await();
+}
+
 #ifdef JANET_WINDOWS
 
 JANET_THREAD_LOCAL HANDLE janet_vm_iocp = NULL;

src/core/os.c

@@ -335,7 +335,6 @@ typedef struct {
     JanetStream *in;
     JanetStream *out;
     JanetStream *err;
-    JanetFiber *fiber;
 #else
     JanetFile *in;
     JanetFile *out;
@@ -345,69 +344,22 @@ typedef struct {
 
 #ifdef JANET_EV
 
-/* Structure used to initialize the thread used to call wait
- * on child processes */
-typedef struct {
-    int write_pipe;
-    JanetProc *proc;
-} JanetReaperInit;
-
-static void *janet_thread_waiter(void *ptr) {
-    JanetReaperInit *init = (JanetReaperInit *)ptr;
-    JanetProc *proc = (JanetProc *) init->proc;
-    int fd = init->write_pipe;
-    pid_t pid = proc->pid;
-    free(init);
-    for (;;) {
-        int status = 0;
-        pid_t which = 0;
-        do {
-            which = waitpid(pid, &status, 0);
-        } while (which == -1 && errno == EINTR);
-        if (which < 0) {
-            /* Error, could not wait or no children to wait on. */
-            break;
-        } else {
-            JanetSelfPipeEvent ev;
-            ev.tag = JANET_SELFPIPE_PROC;
-            ev.as.proc.status = status;
-            ev.as.proc.proc = proc;
-            if (write(fd, &ev, sizeof(ev)) < 0) {
-                /* TODO failed to handle signal. */
-                fprintf(stderr, "failed to write event\n");
-            }
-        }
-    }
-    return NULL;
+/* Function that is called in separate thread to wait on a pid */
+static JanetEVGenericMessage janet_proc_wait_subr(JanetEVGenericMessage args) {
+    JanetProc *proc = (JanetProc *) args.argp;
+    pid_t result;
+    int status = 0;
+    do {
+        result = waitpid(proc->pid, &status, 0);
+    } while (result == -1 && errno == EINTR);
+    args.argi = status;
+    return args;
 }
 
-/* Map pids to JanetProc to allow for lookup after a call to
- * waitpid. */
-static void janet_add_waiting_proc(JanetProc *proc) {
-    JanetReaperInit *init = malloc(sizeof(JanetReaperInit));
-    if (NULL == init) {
-        JANET_OUT_OF_MEMORY;
-    }
-    init->write_pipe = janet_vm_selfpipe[1];
-    init->proc = proc;
-    pthread_attr_t attr;
-    pthread_t waiter_thread;
-    pthread_attr_init(&attr);
-    pthread_attr_setstacksize(&attr, PTHREAD_STACK_MIN);
-    int err = pthread_create(&waiter_thread, NULL, janet_thread_waiter, init);
-    pthread_attr_destroy(&attr);
-    if (err) janet_panicf("%s", strerror(err));
-    pthread_detach(waiter_thread);
-    janet_gcroot(janet_wrap_abstract(proc));
-    janet_ev_inc_refcount();
-}
-
-static void janet_remove_waiting_proc(JanetProc *proc) {
-    janet_gcunroot(janet_wrap_abstract(proc));
-    janet_ev_dec_refcount();
-}
-
-void janet_schedule_proc(void *ptr, int status) {
+/* Callback that is called in main thread when subroutine completes. */
+static void janet_proc_wait_cb(JanetEVGenericMessage args) {
+    int status = args.argi;
+    JanetProc *proc = (JanetProc *) args.argp;
     /* Use POSIX shell semantics for interpreting signals */
     if (WIFEXITED(status)) {
         status = WEXITSTATUS(status);
@@ -416,19 +368,21 @@ void janet_schedule_proc(void *ptr, int status) {
     } else {
         status = WTERMSIG(status) + 128;
     }
-    JanetProc *proc = (JanetProc *)ptr;
-    if (NULL == proc) return;
-    proc->return_code = (int32_t) status;
-    proc->flags |= JANET_PROC_WAITED;
-    proc->flags &= ~JANET_PROC_WAITING;
-    janet_remove_waiting_proc(proc);
-    if ((status != 0) && (proc->flags & JANET_PROC_ERROR_NONZERO)) {
-        JanetString s = janet_formatc("command failed with non-zero exit code %d", status);
-        janet_cancel(proc->fiber, janet_wrap_string(s));
-    } else {
-        janet_schedule(proc->fiber, janet_wrap_integer(status));
+    if (NULL != proc) {
+        proc->return_code = (int32_t) status;
+        proc->flags |= JANET_PROC_WAITED;
+        proc->flags &= ~JANET_PROC_WAITING;
+        janet_gcunroot(janet_wrap_abstract(proc));
+        janet_gcunroot(janet_wrap_fiber(args.fiber));
+        if ((status != 0) && (proc->flags & JANET_PROC_ERROR_NONZERO)) {
+            JanetString s = janet_formatc("command failed with non-zero exit code %d", status);
+            janet_cancel(args.fiber, janet_wrap_string(s));
+        } else {
+            janet_schedule(args.fiber, janet_wrap_integer(status));
+        }
     }
 }
+
 #endif
 
 static int janet_proc_gc(void *p, size_t s) {
@@ -456,9 +410,6 @@ static int janet_proc_mark(void *p, size_t s) {
     if (NULL != proc->in) janet_mark(janet_wrap_abstract(proc->in));
     if (NULL != proc->out) janet_mark(janet_wrap_abstract(proc->out));
     if (NULL != proc->err) janet_mark(janet_wrap_abstract(proc->err));
-#ifdef JANET_EV
-    if (NULL != proc->fiber) janet_mark(janet_wrap_fiber(proc->fiber));
-#endif
     return 0;
 }
 
@@ -470,10 +421,15 @@ static Janet os_proc_wait_impl(JanetProc *proc) {
         janet_panicf("cannot wait twice on a process");
     }
 #ifdef JANET_EV
-    /* Event loop implementation */
-    proc->fiber = janet_root_fiber();
+    /* Event loop implementation - threaded call */
     proc->flags |= JANET_PROC_WAITING;
-    janet_add_waiting_proc(proc);
+    JanetEVGenericMessage targs;
+    memset(&targs, 0, sizeof(targs));
+    targs.argp = proc;
+    targs.fiber = janet_root_fiber();
+    janet_gcroot(janet_wrap_abstract(proc));
+    janet_gcroot(janet_wrap_fiber(targs.fiber));
+    janet_ev_threaded_call(janet_proc_wait_subr, targs, janet_proc_wait_cb);
     janet_await();
 #else
     /* Non evented implementation */
@@ -905,13 +861,22 @@ static Janet os_execute_impl(int32_t argc, Janet *argv, int is_spawn) {
 #else
     proc->pid = pid;
 #endif
-    proc->in = get_stdio_for_handle(new_in, orig_in, 0);
-    proc->out = get_stdio_for_handle(new_out, orig_out, 1);
-    proc->err = get_stdio_for_handle(new_err, orig_err, 1);
-    proc->flags = 0;
-    if (proc->in == NULL || proc->out == NULL || proc->err == NULL) {
-        janet_panic("failed to construct proc");
+    proc->in = NULL;
+    proc->out = NULL;
+    proc->err = NULL;
+    if (new_in != JANET_HANDLE_NONE) {
+        proc->in = get_stdio_for_handle(new_in, orig_in, 0);
+        if (NULL == proc->in) janet_panic("failed to construct proc");
     }
+    if (new_out != JANET_HANDLE_NONE) {
+        proc->out = get_stdio_for_handle(new_out, orig_out, 1);
+        if (NULL == proc->out) janet_panic("failed to construct proc");
+    }
+    if (new_err != JANET_HANDLE_NONE) {
+        proc->err = get_stdio_for_handle(new_err, orig_err, 1);
+        if (NULL == proc->err) janet_panic("failed to construct proc");
+    }
+    proc->flags = 0;
     if (janet_flag_at(flags, 2)) {
         proc->flags |= JANET_PROC_ERROR_NONZERO;
     }
@@ -2173,8 +2138,6 @@ static const JanetReg os_cfuns[] = {
     {NULL, NULL, NULL}
 };
 
-void janet_os_deinit(void) {}
-
 /* Module entry point */
 void janet_lib_os(JanetTable *env) {
 #if !defined(JANET_REDUCED_OS) && defined(JANET_WINDOWS) && defined(JANET_THREADS)

src/core/state.h

@@ -111,6 +111,4 @@ void janet_ev_init(void);
 void janet_ev_deinit(void);
 #endif
 
-void janet_os_deinit(void);
-
 #endif /* JANET_STATE_H_defined */

src/core/util.h

@@ -146,27 +146,6 @@ extern const JanetAbstractType janet_address_type;
 void janet_lib_ev(JanetTable *env);
 void janet_ev_mark(void);
 int janet_make_pipe(JanetHandle handles[2]);
-void janet_schedule_proc(void *proc, int status);
-
-/* Single message that is written to self pipe. This is used
- * to communicate messages inside Janet to work with the event loop.
- * Signals and threads will be the main users of this. */
-typedef struct {
-    enum {
-        JANET_SELFPIPE_PROC
-    } tag;
-    union {
-        struct {
-            int status;
-            void *proc;
-        } proc;
-    } as;
-} JanetSelfPipeEvent;
-
-#ifndef JANET_WINDOWS
-extern JANET_THREAD_LOCAL int janet_vm_selfpipe[2];
-#endif
-
 #endif
 
 #endif

src/core/vm.c

@@ -1505,7 +1505,6 @@ void janet_deinit(void) {
     free(janet_vm_traversal_base);
     janet_vm_fiber = NULL;
     janet_vm_root_fiber = NULL;
-    janet_os_deinit();
 #ifdef JANET_THREADS
     janet_threads_deinit();
 #endif

src/include/janet.h

@@ -1290,6 +1290,48 @@ JANET_API void janet_ev_dec_refcount(void);
 /* Get last error from a an IO operation */
 JANET_API Janet janet_ev_lasterr(void);
 
+/* Async service for calling a function or syscall in a background thread. This is not
+ * as efficient in the slightest as using Streams but can be used for arbitrary blocking
+ * functions and syscalls. */
+
+/* Used to pass data between the main thread and worker threads for simple tasks.
+ * We could just use a pointer but this prevents malloc/free in the common case
+ * of only a handful of arguments. */
+typedef struct {
+    int tag;
+    int argi;
+    void *argp;
+    JanetFiber *fiber;
+} JanetEVGenericMessage;
+
+/* How to resume or cancel after a threaded call. Not exhaustive of the possible
+ * ways one might want to resume after returning from a threaded call, but should
+ * cover most of the common cases. For something more complicated, such as resuming
+ * with an abstract type or a struct, one should use janet_ev_threaded_call instead
+ * of janet_ev_threaded_await with a custom callback. */
+
+#define JANET_EV_TCTAG_NIL 0          /* resume with nil */
+#define JANET_EV_TCTAG_INTEGER 1      /* resume with janet_wrap_integer(argi) */
+#define JANET_EV_TCTAG_STRING 2       /* resume with janet_cstringv((const char *) argp) */
+#define JANET_EV_TCTAG_STRINGF 3      /* resume with janet_cstringv((const char *) argp), then call free on argp. */
+#define JANET_EV_TCTAG_KEYWORD 4      /* resume with janet_ckeywordv((const char *) argp) */
+#define JANET_EV_TCTAG_ERR_STRING 5   /* cancel with janet_cstringv((const char *) argp) */
+#define JANET_EV_TCTAG_ERR_STRINGF 6  /* cancel with janet_cstringv((const char *) argp), then call free on argp. */
+#define JANET_EV_TCTAG_ERR_KEYWORD 7  /* cancel with janet_ckeywordv((const char *) argp) */
+
+/* Function pointer that is run in the thread pool */
+typedef JanetEVGenericMessage(*JanetThreadedSubroutine)(JanetEVGenericMessage arguments);
+
+/* Handler that is run in the main thread with the result of the JanetAsyncSubroutine */
+typedef void (*JanetThreadedCallback)(JanetEVGenericMessage return_value);
+
+/* API calls for quickly offloading some work in C to a new thread or thread pool. */
+JANET_API void janet_ev_threaded_call(JanetThreadedSubroutine fp, JanetEVGenericMessage arguments, JanetThreadedCallback cb);
+JANET_API void janet_ev_threaded_await(JanetThreadedSubroutine fp, int tag, int argi, void *argp);
+
+/* Callback used by janet_ev_threaded_await */
+JANET_API void janet_ev_default_threaded_callback(JanetEVGenericMessage return_value);
+
 /* Read async from a stream */
 JANET_API void janet_ev_read(JanetStream *stream, JanetBuffer *buf, int32_t nbytes);
 JANET_API void janet_ev_readchunk(JanetStream *stream, JanetBuffer *buf, int32_t nbytes);