[console] Sleep while waiting for user input

Reduce CPU usage while waiting for user input.  This is particularly
important for virtual machines, where CPU is a shared resource.

Reported-by: Alessandro Salvatori <alessandro@embrane.com>
Signed-off-by: Michael Brown <mcb30@ipxe.org>

diff --git a/src/core/getkey.c b/src/core/getkey.c
index f16cafa42838419b9fbf950cc2260b7efd617b09..d69cfb44b9c404a31a39236260cbf4a0ba4ff5b6 100644 (file)
--- a/src/core/getkey.c
+++ b/src/core/getkey.c
@@ -24,6 +24,7 @@ FILE_LICENCE ( GPL2_OR_LATER );
 #include <ipxe/process.h>
 #include <ipxe/keys.h>
 #include <ipxe/timer.h>
+#include <ipxe/nap.h>
 
 /** @file
  *
@@ -46,6 +47,7 @@ static int getchar_timeout ( unsigned long timeout ) {
                step();
                if ( iskey() )
                        return getchar();
+               cpu_nap();
        }
 
        return -1;