[PATCH v3 2/2] tools/xenstore: simplify xenstored main loop

[Juergen Gross <jgross@xxxxxxxx>]

The main loop of xenstored is rather complicated due to different
handling of socket and ring-page interfaces. Unify that handling by
introducing interface type specific functions can_read() and
can_write().

Take the opportunity to remove the empty list check before calling
write_messages() because the function is already able to cope with an
empty list.

Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
---
V2:
- split off function vector introduction (Julien Grall)
V3:
- expand commit message (Julien Grall)
---
 tools/xenstore/xenstored_core.c   | 77 +++++++++++++++----------------
 tools/xenstore/xenstored_core.h   |  2 +
 tools/xenstore/xenstored_domain.c |  2 +
 3 files changed, 41 insertions(+), 40 deletions(-)

diff --git a/tools/xenstore/xenstored_core.c b/tools/xenstore/xenstored_core.c
index 856f518075..883a1a582a 100644
--- a/tools/xenstore/xenstored_core.c
+++ b/tools/xenstore/xenstored_core.c
@@ -1659,9 +1659,34 @@ static int readfd(struct connection *conn, void *data, 
unsigned int len)
        return rc;
 }
 
+static bool socket_can_process(struct connection *conn, int mask)
+{
+       if (conn->pollfd_idx == -1)
+               return false;
+
+       if (fds[conn->pollfd_idx].revents & ~(POLLIN | POLLOUT)) {
+               talloc_free(conn);
+               return false;
+       }
+
+       return (fds[conn->pollfd_idx].revents & mask) && !conn->is_ignored;
+}
+
+static bool socket_can_write(struct connection *conn)
+{
+       return socket_can_process(conn, POLLOUT);
+}
+
+static bool socket_can_read(struct connection *conn)
+{
+       return socket_can_process(conn, POLLIN);
+}
+
 const struct interface_funcs socket_funcs = {
        .write = writefd,
        .read = readfd,
+       .can_write = socket_can_write,
+       .can_read = socket_can_read,
 };
 
 static void accept_connection(int sock)
@@ -2296,47 +2321,19 @@ int main(int argc, char *argv[])
                        if (&next->list != &connections)
                                talloc_increase_ref_count(next);
 
-                       if (conn->domain) {
-                               if (domain_can_read(conn))
-                                       handle_input(conn);
-                               if (talloc_free(conn) == 0)
-                                       continue;
-
-                               talloc_increase_ref_count(conn);
-                               if (domain_can_write(conn) &&
-                                   !list_empty(&conn->out_list))
-                                       handle_output(conn);
-                               if (talloc_free(conn) == 0)
-                                       continue;
-                       } else {
-                               if (conn->pollfd_idx != -1) {
-                                       if (fds[conn->pollfd_idx].revents
-                                           & ~(POLLIN|POLLOUT))
-                                               talloc_free(conn);
-                                       else if ((fds[conn->pollfd_idx].revents
-                                                 & POLLIN) &&
-                                                !conn->is_ignored)
-                                               handle_input(conn);
-                               }
-                               if (talloc_free(conn) == 0)
-                                       continue;
-
-                               talloc_increase_ref_count(conn);
-
-                               if (conn->pollfd_idx != -1) {
-                                       if (fds[conn->pollfd_idx].revents
-                                           & ~(POLLIN|POLLOUT))
-                                               talloc_free(conn);
-                                       else if ((fds[conn->pollfd_idx].revents
-                                                 & POLLOUT) &&
-                                                !conn->is_ignored)
-                                               handle_output(conn);
-                               }
-                               if (talloc_free(conn) == 0)
-                                       continue;
+                       if (conn->funcs->can_read(conn))
+                               handle_input(conn);
+                       if (talloc_free(conn) == 0)
+                               continue;
 
-                               conn->pollfd_idx = -1;
-                       }
+                       talloc_increase_ref_count(conn);
+
+                       if (conn->funcs->can_write(conn))
+                               handle_output(conn);
+                       if (talloc_free(conn) == 0)
+                               continue;
+
+                       conn->pollfd_idx = -1;
                }
 
                if (delayed_requests) {
diff --git a/tools/xenstore/xenstored_core.h b/tools/xenstore/xenstored_core.h
index 6c4845c196..bb36111ecc 100644
--- a/tools/xenstore/xenstored_core.h
+++ b/tools/xenstore/xenstored_core.h
@@ -90,6 +90,8 @@ struct connection;
 struct interface_funcs {
        int (*write)(struct connection *, const void *, unsigned int);
        int (*read)(struct connection *, void *, unsigned int);
+       bool (*can_write)(struct connection *);
+       bool (*can_read)(struct connection *);
 };
 
 struct connection
diff --git a/tools/xenstore/xenstored_domain.c 
b/tools/xenstore/xenstored_domain.c
index f3cd56050e..708bf68af0 100644
--- a/tools/xenstore/xenstored_domain.c
+++ b/tools/xenstore/xenstored_domain.c
@@ -175,6 +175,8 @@ static int readchn(struct connection *conn, void *data, 
unsigned int len)
 static const struct interface_funcs domain_funcs = {
        .write = writechn,
        .read = readchn,
+       .can_write = domain_can_write,
+       .can_read = domain_can_read,
 };
 
 static void *map_interface(domid_t domid)
-- 
2.26.2