net/tcp: Only call grub_get_time_ms() when there are sockets to potentially retransmi...

If the machine has network cards found, but there are no tcp open sockets
(because the user doesn't use the network to boot), then grub_net_tcp_retransmit()
should be a noop. Thus GRUB doesn't need to call grub_get_time_ms(), which
does a call into firmware on powerpc-ieee1275, and probably other targets.
So only call grub_get_time_ms() if there are tcp sockets.

Aside from improving performance, its also useful to stay out of the firmware
as much as possible when debugging via QEMU because its a pain to get back
in to GRUB execution. grub_net_tcp_retransmit() can get called very frequently
via grub_net_poll_cards_idle() when GRUB is waiting for a keypress
(grub_getkey_noblock() calls grub_net_poll_cards_idle()). This can be annoying
when debugging an issue in GRUB on PowerPC in QEMU with GDB when GRUB is waiting
for a keypress because interrupting via GDB nearly always lands in the OpenBIOS
firmware's milliseconds call.

Signed-off-by: Glenn Washburn <development@efficientek.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>

diff --git a/grub-core/net/tcp.c b/grub-core/net/tcp.c
index 2004601212ac3f4a395234eae74f1b840f11d7c3..93dee0caa1b7283e47a7a03f5a8cd85380733e72 100644 (file)
--- a/grub-core/net/tcp.c
+++ b/grub-core/net/tcp.c
@@ -362,8 +362,13 @@ void
 grub_net_tcp_retransmit (void)
 {
   grub_net_tcp_socket_t sock;
-  grub_uint64_t ctime = grub_get_time_ms ();
-  grub_uint64_t limit_time = ctime - TCP_RETRANSMISSION_TIMEOUT;
+  grub_uint64_t ctime = 0, limit_time = 0;
+
+  if (tcp_sockets != NULL)
+    {
+      ctime = grub_get_time_ms ();
+      limit_time = ctime - TCP_RETRANSMISSION_TIMEOUT;
+    }
 
   FOR_TCP_SOCKETS (sock)
   {