Fix race condition when calling meshlink_stop() immediately after meshlink_start().

[meshlink] / src / event.c

diff --git a/src/event.c b/src/event.c
index 065f1b5eaf5a52710f8c9412ddccd03b656e8f90..1f6ea186330ccdad0ea034c18ff621fc63febb04 100644 (file)
--- a/src/event.c
+++ b/src/event.c
@@ -26,9 +26,6 @@
 #include "utils.h"
 #include "xalloc.h"
 
-event_loop_t *loop;
-struct timeval now;
-
 static int io_compare(const io_t *a, const io_t *b) {
        return a->fd - b->fd;
 }
@@ -84,6 +81,8 @@ void io_del(event_loop_t *loop, io_t *io) {
        if(!io->cb)
                return;
 
+       loop->deletion = true;
+
        io_set(loop, io, 0);
 
        splay_unlink_node(&loop->ios, &io->node);
@@ -91,6 +90,9 @@ void io_del(event_loop_t *loop, io_t *io) {
 }
 
 void timeout_add(event_loop_t *loop, timeout_t *timeout, timeout_cb_t cb, void *data, struct timeval *tv) {
+       if(!timeout->cb)
+               timeout->tv = (struct timeval){0, 0};
+
        timeout->cb = cb;
        timeout->data = data;
        timeout->node.data = timeout;
@@ -115,6 +117,8 @@ void timeout_del(event_loop_t *loop, timeout_t *timeout) {
        if(!timeout->cb)
                return;
 
+       loop->deletion = true;
+
        splay_unlink_node(&loop->timeouts, &timeout->node);
        timeout->cb = 0;
        timeout->tv = (struct timeval){0, 0};
@@ -139,6 +143,14 @@ static void pipe_init(event_loop_t *loop) {
                io_add(loop, &loop->signalio, signalio_handler, NULL, loop->pipefd[0], IO_READ);
 }
 
+void signal_trigger(event_loop_t *loop, signal_t *sig) {
+
+       uint8_t signum = sig->signum;
+       write(loop->pipefd[1], &signum, 1);
+       return;
+
+}
+
 void signal_add(event_loop_t *loop, signal_t *sig, signal_cb_t cb, void *data, uint8_t signum) {
        if(sig->cb)
                return;
@@ -159,20 +171,24 @@ void signal_del(event_loop_t *loop, signal_t *sig) {
        if(!sig->cb)
                return;
 
+       loop->deletion = true;
+
        splay_unlink_node(&loop->signals, &sig->node);
        sig->cb = NULL;
 }
 
-bool event_loop_run(event_loop_t *loop) {
-       loop->running = true;
+void idle_set(event_loop_t *loop, idle_cb_t cb, void *data) {
+       loop->idle_cb = cb;
+       loop->idle_data = data;
+}
 
+bool event_loop_run(event_loop_t *loop, pthread_mutex_t *mutex) {
        fd_set readable;
        fd_set writable;
 
        while(loop->running) {
                gettimeofday(&loop->now, NULL);
-               now = loop->now;
-               struct timeval diff, *tv = NULL;
+               struct timeval diff, it, *tv = NULL;
 
                while(loop->timeouts.head) {
                        timeout_t *timeout = loop->timeouts.head->data;
@@ -188,6 +204,12 @@ bool event_loop_run(event_loop_t *loop) {
                        }
                }
 
+               if(loop->idle_cb) {
+                       it = loop->idle_cb(loop, loop->idle_data);
+                       if(it.tv_sec >= 0 && (!tv || timercmp(&it, tv, <)))
+                               tv = &it;
+               }
+
                memcpy(&readable, &loop->readfds, sizeof readable);
                memcpy(&writable, &loop->writefds, sizeof writable);
 
@@ -198,7 +220,12 @@ bool event_loop_run(event_loop_t *loop) {
                        fds = last->fd + 1;
                }
 
+               // release mesh mutex during select
+               if(mutex)
+                       pthread_mutex_unlock(mutex);
                int n = select(fds, &readable, &writable, NULL, tv);
+               if(mutex)
+                       pthread_mutex_lock(mutex);
 
                if(n < 0) {
                        if(sockwouldblock(errno))
@@ -210,11 +237,21 @@ bool event_loop_run(event_loop_t *loop) {
                if(!n)
                        continue;
 
+               // Normally, splay_each allows the current node to be deleted. However,
+               // it can be that one io callback triggers the deletion of another io,
+               // so we have to detect this and break the loop.
+
+               loop->deletion = false;
+
                for splay_each(io_t, io, &loop->ios) {
-                       if(FD_ISSET(io->fd, &writable))
+                       if(FD_ISSET(io->fd, &writable) && io->cb)
                                io->cb(loop, io->data, IO_WRITE);
-                       else if(FD_ISSET(io->fd, &readable))
+                       if(loop->deletion)
+                               break;
+                       if(FD_ISSET(io->fd, &readable) && io->cb)
                                io->cb(loop, io->data, IO_READ);
+                       if(loop->deletion)
+                               break;
                }
        }
 
@@ -227,6 +264,10 @@ void event_flush_output(event_loop_t *loop) {
                        io->cb(loop, io->data, IO_WRITE);
 }
 
+void event_loop_start(event_loop_t *loop) {
+       loop->running = true;
+}
+
 void event_loop_stop(event_loop_t *loop) {
        loop->running = false;
 }
@@ -237,13 +278,14 @@ void event_loop_init(event_loop_t *loop) {
        loop->signals.compare = (splay_compare_t)signal_compare;
        loop->pipefd[0] = -1;
        loop->pipefd[1] = -1;
+       gettimeofday(&loop->now, NULL);
 }
 
 void event_loop_exit(event_loop_t *loop) {
        for splay_each(io_t, io, &loop->ios)
-               splay_free_node(&loop->ios, node);
+               splay_unlink_node(&loop->ios, node);
        for splay_each(timeout_t, timeout, &loop->timeouts)
-               splay_free_node(&loop->timeouts, node);
+               splay_unlink_node(&loop->timeouts, node);
        for splay_each(signal_t, signal, &loop->signals)
-               splay_free_node(&loop->signals, node);
+               splay_unlink_node(&loop->signals, node);
 }