Add io_select_timeout to the io interface

This change fixes a problem that can occur with non-blocking (and also
blocking for very short times) select/poll calls. The problem occurs because
the timeout is implemented at the client side. For a non-blocking call, this
means that (depending on the code path taken in the C library) the client
could get a timeout without a full RPC round-trip to the server. Moving the
implementation of the timeout to the servers guarantees a full round-trip,
and correct results for non-blocking calls.

The modifications in this change depend on the availability of the recently
added pthread_hurd_cond_timedwait_np function in libpthread.

* boot/boot.c (io_select_common): New static function.
(S_io_select): Use io_select_common.
(S_io_select_timeout): New function which makes use of io_select_common.
* console-client/kbd-repeat.c (repeater_select): Add a timeout parameter.
* console-client/pc-mouse.c (repeater_select): Likewise.
* console-client/trans.c (io_select_common): New static function.
(netfs_S_io_select): Use io_select_common.
(netfs_S_io_select_timeout): New function which makes use of io_select_common.
* console-client/trans.h (struct consnode): Add a timeout parameter.
* hurd/io.defs (io_select_timeout): New MIG routine.
* hurd/io_reply.defs (io_select_timeout_reply): New MIG simpleroutine.
* hurd/io_request.defs (io_select_timeout_request): Likewise.
* libdiskfs/io-select.c (diskfs_S_io_select_timeout): New function.
* libnetfs/io-select.c (netfs_S_io_select_timeout): Likewise.
* libpipe/pipe.c (pipe_pair_select): Add a timeout parameter.
* libpipe/pipe.h (pipe_select_readable): Likewise.
(pipe_select_writable): Likewise.
(pipe_pair_select): Likewise.
* libpipe/pq.h: Include <hurd/hurd_types.h>.
* libtrivfs/io-select.c (trivfs_S_io_select_timeout): New function.
* pfinet/glue-include/linux/sched.h: Include <errno.h>.
(interruptible_sleep_on): Function removed, replaced with ...
(interruptible_sleep_on_timeout): New function.
(schedule): Update to use interruptible_sleep_on_timeout.
(schedule_timeout): Likewise.
* pfinet/io-ops.c (io_select_common): New static function.
(S_io_select): Use io_select_common.
(S_io_select_timeout): New function which makes use of io_select_common.
* pfinet/tunnel.c (io_select_common): New static function.
(trivfs_S_io_select): Use io_select_common.
(trivfs_S_io_select_timeout): New function which makes use of io_select_common.
* pflocal/connq.c (connq_listen): Replace noblock with a timeout parameter.
* pflocal/connq.h: Include <hurd/hurd_types.h>.
(connq_listen): Update declaration to replace noblock with a timeout parameter.
* pflocal/io.c (io_select_common): New static function.
(S_io_select): Use io_select_common.
(S_io_select_timeout): New function which makes use of io_select_common.
* pflocal/socket.c (S_socket_accept): Update call to connq_listen to match new
declaration.
* storeio/io.c (trivfs_S_io_select_timeout): New function.
* term/ptyio.c (pty_io_select): Add a timeout parameter.
* term/term.h (pty_io_select): Likewise.
* term/users.c (io_select_common): New static function.
(trivfs_S_io_select): Use io_select_common.
(trivfs_S_io_select_timeout): New function which makes use of io_select_common.
* trans/fifo.c (io_select_common): New static function.
(trivfs_S_io_select): Use io_select_common.
(trivfs_S_io_select_timeout): New function which makes use of io_select_common.
* trans/firmlink.c (trivfs_S_io_select_timeout): New function.
* trans/new-fifo.c (io_select_common): New static function.
(trivfs_S_io_select): Use io_select_common.
(trivfs_S_io_select_timeout): New function which makes use of io_select_common.
* trans/null.c (trivfs_S_io_select_timeout): New function.
* trans/streamio.c (io_select_common): New static function.
(trivfs_S_io_select): Use io_select_common.
(trivfs_S_io_select_timeout): New function which makes use of io_select_common.

4 files changed, 52 insertions, 17 deletions

diff --git a/pflocal/connq.c b/pflocal/connq.c
index ab2b3a55..d88711e3 100644
--- a/pflocal/connq.c
+++ b/pflocal/connq.c
@@ -141,16 +141,19 @@ connq_destroy (struct connq *cq)
 /* ---------------------------------------------------------------- */
 
 /* Return a connection request on CQ.  If SOCK is NULL, the request is
-   left in the queue.  If NOBLOCK is true, EWOULDBLOCK is returned
-   when there are no immediate connections available.  */
+   left in the queue.  If TIMEOUT denotes a value of 0, EWOULDBLOCK is
+   returned when there are no immediate connections available.
+   Otherwise this value is used to limit the wait duration.  If TIMEOUT
+   is NULL, the wait duration isn't bounded.  */
 error_t
-connq_listen (struct connq *cq, int noblock, struct sock **sock)
+connq_listen (struct connq *cq, struct timespec *tsp, struct sock **sock)
 {
   error_t err = 0;
 
   pthread_mutex_lock (&cq->lock);
 
-  if (noblock && cq->count == 0 && cq->num_connectors == 0)
+  if (tsp && tsp->tv_sec == 0 && tsp->tv_nsec == 0 && cq->count == 0
+      && cq->num_connectors == 0)
     {
       pthread_mutex_unlock (&cq->lock);
       return EWOULDBLOCK;
@@ -176,12 +179,14 @@ connq_listen (struct connq *cq, int noblock, struct sock **sock)
 	pthread_cond_signal (&cq->connectors);
 
       do
-	if (pthread_hurd_cond_wait_np (&cq->listeners, &cq->lock))
+	{
+	  err = pthread_hurd_cond_timedwait_np (&cq->listeners, &cq->lock, tsp);
+	  if (err)
 	  {
 	    cq->num_listeners--;
-	    err = EINTR;
 	    goto out;
 	  }
+	}
       while (cq->count == 0);
     }
 
diff --git a/pflocal/connq.h b/pflocal/connq.h
index 9278d007..71583800 100644
--- a/pflocal/connq.h
+++ b/pflocal/connq.h
@@ -36,9 +36,12 @@ error_t connq_create (struct connq **cq);
 void connq_destroy (struct connq *cq);
 
 /* Return a connection request on CQ.  If SOCK is NULL, the request is
-   left in the queue.  If NOBLOCK is true, EWOULDBLOCK is returned
-   when there are no immediate connections available.  */
-error_t connq_listen (struct connq *cq, int noblock, struct sock **sock);
+   left in the queue.  If TIMEOUT denotes a value of 0, EWOULDBLOCK is
+   returned when there are no immediate connections available.
+   Otherwise this value is used to limit the wait duration.  If TIMEOUT
+   is NULL, the wait duration isn't bounded.  */
+error_t connq_listen (struct connq *cq, struct timespec *tsp,
+		      struct sock **sock);
 
 /* Try to connect SOCK with the socket listening on CQ.  If NOBLOCK is
    true, then return EWOULDBLOCK if there are no connections
diff --git a/pflocal/io.c b/pflocal/io.c
index 2301611e..0dec56e0 100644
--- a/pflocal/io.c
+++ b/pflocal/io.c
@@ -172,10 +172,10 @@ S_io_duplicate (struct sock_user *user,
 /* SELECT_TYPE is the bitwise OR of SELECT_READ, SELECT_WRITE, and SELECT_URG.
    Block until one of the indicated types of i/o can be done "quickly", and
    return the types that are then available.  */
-error_t
-S_io_select (struct sock_user *user,
-	     mach_port_t reply, mach_msg_type_name_t reply_type,
-	     int *select_type)
+static error_t
+io_select_common (struct sock_user *user,
+		  mach_port_t reply, mach_msg_type_name_t reply_type,
+		  struct timespec *tsp, int *select_type)
 {
   error_t err = 0;
   struct sock *sock;
@@ -199,16 +199,24 @@ S_io_select (struct sock_user *user,
 
       if (*select_type & SELECT_READ)
 	{
+	  struct timespec noblock = {0, 0};
+
 	  /* Wait for a connect.  Passing in NULL for SOCK means that
 	     the request won't be dequeued.  */
-	  if (connq_listen (sock->listen_queue, 1, NULL) == 0)
+	  if (connq_listen (sock->listen_queue, &noblock, NULL) == 0)
 	    /* We can satisfy this request immediately. */
 	    return 0;
 	  else
 	    /* Gotta wait...  */
 	    {
 	      ports_interrupt_self_on_port_death (user, reply);
-	      return connq_listen (sock->listen_queue, 0, NULL);
+	      err = connq_listen (sock->listen_queue, tsp, NULL);
+	      if (err == ETIMEDOUT)
+		{
+		  *select_type = 0;
+		  err = 0;
+		}
+	      return err;
 	    }
 	}
     }
@@ -261,7 +269,7 @@ S_io_select (struct sock_user *user,
 	/* Wait for something to change.  */
 	{
 	  ports_interrupt_self_on_port_death (user, reply);
-	  err = pipe_pair_select (read_pipe, write_pipe, select_type, 1);
+	  err = pipe_pair_select (read_pipe, write_pipe, tsp, select_type, 1);
 	}
 
       if (valid & SELECT_READ)
@@ -272,6 +280,23 @@ S_io_select (struct sock_user *user,
 
   return err;
 }
+
+error_t
+S_io_select (struct sock_user *user,
+	     mach_port_t reply, mach_msg_type_name_t reply_type,
+	     int *select_type)
+{
+  return io_select_common (user, reply, reply_type, NULL, select_type);
+}
+
+error_t
+S_io_select_timeout (struct sock_user *user,
+		     mach_port_t reply, mach_msg_type_name_t reply_type,
+		     struct timespec ts,
+		     int *select_type)
+{
+  return io_select_common (user, reply, reply_type, &ts, select_type);
+}
 
 /* Return the current status of the object.  Not all the fields of the
    io_statuf_t are meaningful for all objects; however, the access and
diff --git a/pflocal/socket.c b/pflocal/socket.c
index 65da7487..ce1edd82 100644
--- a/pflocal/socket.c
+++ b/pflocal/socket.c
@@ -178,9 +178,11 @@ S_socket_accept (struct sock_user *user,
   err = ensure_connq (sock);
   if (!err)
     {
+      struct timespec noblock = {0, 0};
       struct sock *peer_sock;
 
-      err = connq_listen (sock->listen_queue, sock->flags & SOCK_NONBLOCK,
+      err = connq_listen (sock->listen_queue,
+			  (sock->flags & SOCK_NONBLOCK) ? &noblock : NULL,
 			  &peer_sock);
       if (!err)
 	{