[ipxe-devel] [PATCH 1/1] efi: provide possibility to disable cpu_nap

[Heinrich Schuchardt]

U-Boot runs single-threaded without interrupts.
When cpu_nap is called the process is never woken up again.

With the patch we can use environment variable CPUNONAP
to disable cpu_nap when building iPXE, e.g.

	CPUNONAP=1

Signed-off-by: Heinrich Schuchardt <xypron.glpk at gmx.de>
---
 src/Makefile.housekeeping |  5 +++++
 src/core/console.c        |  2 ++
 src/core/gdbudp.c         |  2 ++
 src/core/getkey.c         |  2 ++
 src/core/timer.c          |  2 ++
 src/doc/build_sys.dox     | 13 +++++++++++++
 6 files changed, 26 insertions(+)

diff --git a/src/Makefile.housekeeping b/src/Makefile.housekeeping
index f09db372..2c47f691 100644
--- a/src/Makefile.housekeeping
+++ b/src/Makefile.housekeeping
@@ -769,6 +769,11 @@ ifneq ($(PROFILE),)
 CFLAGS	+= -DPROFILING=$(PROFILE)
 endif
 
+# Do not let the cpu sleep when waiting for input
+ifneq ($(CPUNONAP),)
+CFLAGS	+= -DCPUNONAP=1
+endif
+
 include/ipxe/profile.h : $(PROFILE_LIST)
 	$(Q)$(TOUCH) $@
 
diff --git a/src/core/console.c b/src/core/console.c
index 7fd00036..1cab3db8 100644
--- a/src/core/console.c
+++ b/src/core/console.c
@@ -98,7 +98,9 @@ int getchar ( void ) {
 		 * makes Etherboot waiting for user interaction waste a lot
 		 * less CPU time in a VMware session.
 		 */
+#ifndef CPUNODEF
 		cpu_nap();
+#endif
 
 		/* Keep processing background tasks while we wait for
 		 * input.
diff --git a/src/core/gdbudp.c b/src/core/gdbudp.c
index e4613d13..af23f859 100644
--- a/src/core/gdbudp.c
+++ b/src/core/gdbudp.c
@@ -156,7 +156,9 @@ static size_t gdbudp_recv ( char *buf, size_t len ) {
 bad_packet:
 			free_iob ( iob );
 		}
+#ifndef CPUNODEF
 		cpu_nap();
+#endif
 	}
 }
 
diff --git a/src/core/getkey.c b/src/core/getkey.c
index 0c280d23..f515c340 100644
--- a/src/core/getkey.c
+++ b/src/core/getkey.c
@@ -51,7 +51,9 @@ static int getchar_timeout ( unsigned long timeout ) {
 		step();
 		if ( iskey() )
 			return getchar();
+#ifndef CPUNONAP
 		cpu_nap();
+#endif
 	}
 
 	return -1;
diff --git a/src/core/timer.c b/src/core/timer.c
index 24745cef..720966fa 100644
--- a/src/core/timer.c
+++ b/src/core/timer.c
@@ -106,7 +106,9 @@ static unsigned int sleep_interruptible ( unsigned int secs,
 			step();
 			if ( interrupted && interrupted() )
 				return secs;
+#ifndef CPUNONAP
 			cpu_nap();
+#endif
 		}
 		start = now;
 	}
diff --git a/src/doc/build_sys.dox b/src/doc/build_sys.dox
index 9466f662..28350c46 100644
--- a/src/doc/build_sys.dox
+++ b/src/doc/build_sys.dox
@@ -77,6 +77,19 @@ You can see the full list of object files that will be built using
 
 @endcode
 
+ at subsection comp_envir Environment variables influencing compilation
+
+In some loops function cpu_nap() is used to wait for an interrupt.
+In single threaded environments without interrupt like U-Boot EFI
+iPXE will never be woken up. cpu_nap() can be disabled by defining
+the following environment variable value before calling make:
+
+ at code
+
+	CPUNONAP=1
+
+ at endcode
+
 @subsection comp_ar After compilation
 
 Once all objects have been compiled, they will be collected into a
-- 
2.11.0