uloop: fix corner cases with recursive uloop_run calls

With multiple recursive calls to uloop_run, the callback for the same fd
can be run multiple times from different levels in the stack.
Prevent this by tracking the stack of uloop_fd callbacks and buffering new
incoming events for fds already on the stack.

Signed-off-by: Felix Fietkau <nbd@openwrt.org>

diff --git a/uloop.c b/uloop.c
index bf13199f881db3b6d5cb92fd3002e846fa888304..54ebe8d7b0ab05c7e1724ea3d05b1512f0ff9b6b 100644 (file)
--- a/uloop.c
+++ b/uloop.c
@@ -43,6 +43,14 @@ struct uloop_fd_event {
        unsigned int events;
 };
 
+struct uloop_fd_stack {
+       struct uloop_fd_stack *next;
+       struct uloop_fd *fd;
+       unsigned int events;
+};
+
+static struct uloop_fd_stack *fd_stack = NULL;
+
 #define ULOOP_MAX_EVENTS 10
 
 static struct list_head timeouts = LIST_HEAD_INIT(timeouts);
@@ -285,6 +293,32 @@ static int uloop_fetch_events(int timeout)
 
 #endif
 
+static bool uloop_fd_stack_event(struct uloop_fd *fd, int events)
+{
+       struct uloop_fd_stack *cur;
+
+       /*
+        * Do not buffer events for level-triggered fds, they will keep firing.
+        * Caller needs to take care of recursion issues.
+        */
+       if (!(fd->flags & ULOOP_EDGE_TRIGGER))
+               return false;
+
+       for (cur = fd_stack; cur; cur = cur->next) {
+               if (cur->fd != fd)
+                       continue;
+
+               if (events < 0)
+                       cur->fd = NULL;
+               else
+                       cur->events |= events | ULOOP_EVENT_BUFFERED;
+
+               return true;
+       }
+
+       return false;
+}
+
 static void uloop_run_events(int timeout)
 {
        struct uloop_fd_event *cur;
@@ -298,17 +332,33 @@ static void uloop_run_events(int timeout)
        }
 
        while (cur_nfds > 0) {
+               struct uloop_fd_stack stack_cur;
+               unsigned int events;
+
                cur = &cur_fds[cur_fd++];
                cur_nfds--;
 
                fd = cur->fd;
+               events = cur->events;
                if (!fd)
                        continue;
 
                if (!fd->cb)
                        continue;
 
-               fd->cb(fd, cur->events);
+               if (uloop_fd_stack_event(fd, cur->events))
+                       continue;
+
+               stack_cur.next = fd_stack;
+               stack_cur.fd = fd;
+               fd_stack = &stack_cur;
+               do {
+                       stack_cur.events = 0;
+                       fd->cb(fd, events);
+                       events = stack_cur.events & ULOOP_EVENT_MASK;
+               } while (stack_cur.fd && events);
+               fd_stack = stack_cur.next;
+
                return;
        }
 }
@@ -352,6 +402,7 @@ int uloop_fd_delete(struct uloop_fd *fd)
                cur_fds[cur_fd + i].fd = NULL;
        }
        fd->registered = false;
+       uloop_fd_stack_event(fd, -1);
        return __uloop_fd_delete(fd);
 }
 

diff --git a/uloop.h b/uloop.h
index 39b9b582336efe7780ea6c36a6f24c77277c963f..98dd8184a4f2fa6e566dd86cfd1b779b2fae7f4d 100644 (file)
--- a/uloop.h
+++ b/uloop.h
@@ -44,8 +44,13 @@ typedef void (*uloop_process_handler)(struct uloop_process *c, int ret);
 #define ULOOP_WRITE            (1 << 1)
 #define ULOOP_EDGE_TRIGGER     (1 << 2)
 #define ULOOP_BLOCKING         (1 << 3)
+
+#define ULOOP_EVENT_MASK       (ULOOP_READ | ULOOP_WRITE)
+
+/* internal flags */
+#define ULOOP_EVENT_BUFFERED   (1 << 4)
 #ifdef USE_KQUEUE
-#define ULOOP_EDGE_DEFER       (1 << 4)
+#define ULOOP_EDGE_DEFER       (1 << 5)
 #endif
 
 struct uloop_fd