ccan/io: keep always pointers to plans, not a linked list.

Duplex io_conns can be in the always list twice, and it was a source
of bugs, but I didn't want to add a second list_node.  Since there are
not many always at once, it's better (and more space-efficient) to use
a simple pointer array.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

diff --git a/ccan/io/backend.h b/ccan/io/backend.h
index c071c5d6c5939372bcbb290a0a580e5257076e38..d877e44e1580cd66f8646b8abb414dc157abfb0a 100644 (file)
--- a/ccan/io/backend.h
+++ b/ccan/io/backend.h
@@ -60,9 +60,6 @@ struct io_plan {
 struct io_conn {
        struct fd fd;
 
-       /* always list. */
-       struct list_node always;
-
        void (*finish)(struct io_conn *, void *arg);
        void *finish_arg;
 
@@ -76,15 +73,14 @@ bool add_conn(struct io_conn *c);
 bool add_duplex(struct io_conn *c);
 void del_listener(struct io_listener *l);
 void cleanup_conn_without_close(struct io_conn *c);
-void backend_new_always(struct io_conn *conn);
+bool backend_new_always(struct io_plan *plan);
 void backend_new_plan(struct io_conn *conn);
-void remove_from_always(struct io_conn *conn);
 void backend_plan_done(struct io_conn *conn);
 
 void backend_wake(const void *wait);
 
 void io_ready(struct io_conn *conn, int pollflags);
-void io_do_always(struct io_conn *conn);
+void io_do_always(struct io_plan *conn);
 void io_do_wakeup(struct io_conn *conn, enum io_direction dir);
 void *do_io_loop(struct io_conn **ready);
 #endif /* CCAN_IO_BACKEND_H */

diff --git a/ccan/io/io.c b/ccan/io/io.c
index c5c9bee0daf0329f433eec930058bfd20905f96c..7ebd5a202d7899f356ed1963eb3c6f463ee986e2 100644 (file)
--- a/ccan/io/io.c
+++ b/ccan/io/io.c
@@ -97,7 +97,6 @@ struct io_conn *io_new_conn_(const tal_t *ctx, int fd,
        conn->fd.fd = fd;
        conn->finish = NULL;
        conn->finish_arg = NULL;
-       list_node_init(&conn->always);
 
        if (!add_conn(conn))
                return tal_free(conn);
@@ -145,7 +144,9 @@ static struct io_plan *set_always(struct io_conn *conn,
        struct io_plan *plan = &conn->plan[dir];
 
        plan->status = IO_ALWAYS;
-       backend_new_always(conn);
+       /* Only happens on OOM, and only with non-default tal_backend. */
+       if (!backend_new_always(plan))
+               return NULL;
        return io_set_plan(conn, dir, NULL, next, arg);
 }
 
@@ -414,27 +415,14 @@ void io_ready(struct io_conn *conn, int pollflags)
                        || conn->plan[IO_IN].status == IO_POLLING_STARTED);
 }
 
-void io_do_always(struct io_conn *conn)
+void io_do_always(struct io_plan *plan)
 {
-       /* There's a corner case where the in next_plan wakes up the
-        * out, placing it in IO_ALWAYS and we end up processing it immediately,
-        * only to leave it in the always list.
-        *
-        * Yet we can't just process one, in case they are both supposed
-        * to be done, so grab state beforehand.
-        */
-       bool always_out = (conn->plan[IO_OUT].status == IO_ALWAYS);
+       struct io_conn *conn;
 
-       if (conn->plan[IO_IN].status == IO_ALWAYS)
-               if (!next_plan(conn, &conn->plan[IO_IN]))
-                       return;
+       assert(plan->status == IO_ALWAYS);
+       conn = container_of(plan, struct io_conn, plan[plan->dir]);
 
-       if (always_out) {
-               /* You can't *unalways* a conn (except by freeing, in which
-                * case next_plan() returned false */
-               assert(conn->plan[IO_OUT].status == IO_ALWAYS);
-               next_plan(conn, &conn->plan[IO_OUT]);
-       }
+       next_plan(conn, plan);
 }
 
 void io_do_wakeup(struct io_conn *conn, enum io_direction dir)

diff --git a/ccan/io/poll.c b/ccan/io/poll.c
index b005a97e4b1d07879a4e281a8d48276baaac2fa1..a853c8705f1d5b68971327ec9c38d22ef4222e2b 100644 (file)
--- a/ccan/io/poll.c
+++ b/ccan/io/poll.c
@@ -11,11 +11,10 @@
 #include <ccan/time/time.h>
 #include <ccan/timer/timer.h>
 
-static size_t num_fds = 0, max_fds = 0, num_waiting = 0;
+static size_t num_fds = 0, max_fds = 0, num_waiting = 0, num_always = 0, max_always = 0;
 static struct pollfd *pollfds = NULL;
 static struct fd **fds = NULL;
-static LIST_HEAD(closing);
-static LIST_HEAD(always);
+static struct io_plan **always = NULL;
 static struct timemono (*nowfn)(void) = time_mono;
 static int (*pollfn)(struct pollfd *fds, nfds_t nfds, int timeout) = poll;
 
@@ -110,16 +109,52 @@ bool add_listener(struct io_listener *l)
        return true;
 }
 
-void remove_from_always(struct io_conn *conn)
+static int find_always(const struct io_plan *plan)
 {
-       list_del_init(&conn->always);
+       for (size_t i = 0; i < num_always; i++)
+               if (always[i] == plan)
+                       return i;
+       return -1;
 }
 
-void backend_new_always(struct io_conn *conn)
+static void remove_from_always(const struct io_plan *plan)
 {
-       /* In case it's already in always list. */
-       list_del(&conn->always);
-       list_add_tail(&always, &conn->always);
+       int pos;
+
+       if (plan->status != IO_ALWAYS)
+               return;
+
+       pos = find_always(plan);
+       assert(pos >= 0);
+
+       /* Move last one down if we made a hole */
+       if (pos != num_always-1)
+               always[pos] = always[num_always-1];
+       num_always--;
+}
+
+bool backend_new_always(struct io_plan *plan)
+{
+       assert(find_always(plan) == -1);
+
+       if (!max_always) {
+               assert(num_always == 0);
+               always = tal_arr(NULL, struct io_plan *, 8);
+               if (!always)
+                       return false;
+               max_always = 8;
+       }
+
+       if (num_always + 1 > max_always) {
+               size_t num = max_always * 2;
+
+               if (!tal_resize(&always, num))
+                       return false;
+               max_always = num;
+       }
+
+       always[num_always++] = plan;
+       return true;
 }
 
 void backend_new_plan(struct io_conn *conn)
@@ -174,8 +209,9 @@ static void destroy_conn(struct io_conn *conn, bool close_fd)
        if (close_fd)
                close(conn->fd.fd);
        del_fd(&conn->fd);
-       /* In case it's on always list, remove it. */
-       list_del_init(&conn->always);
+
+       remove_from_always(&conn->plan[IO_IN]);
+       remove_from_always(&conn->plan[IO_OUT]);
 
        /* errno saved/restored by tal_free itself. */
        if (conn->finish) {
@@ -217,15 +253,12 @@ static void accept_conn(struct io_listener *l)
 static bool handle_always(void)
 {
        bool ret = false;
-       struct io_conn *conn;
-
-       while ((conn = list_pop(&always, struct io_conn, always)) != NULL) {
-               assert(conn->plan[IO_IN].status == IO_ALWAYS
-                      || conn->plan[IO_OUT].status == IO_ALWAYS);
 
-               /* Re-initialize, for next time. */
-               list_node_init(&conn->always);
-               io_do_always(conn);
+       while (num_always > 0) {
+               /* Remove first: it might re-add */
+               struct io_plan *plan = always[num_always-1];
+               num_always--;
+               io_do_always(plan);
                ret = true;
        }
        return ret;