[PATCH] uml: fix unreasonably long udelay

Currently we have a confused udelay implementation.

* __const_udelay does not accept usecs but xloops in i386 and x86_64
* our implementation requires usecs as arg
* it gets a xloops count when called by asm/arch/delay.h

Bugs related to this (extremely long shutdown times) where reported by some
x86_64 users, especially using Device Mapper.

To hit this bug, a compile-time constant time parameter must be passed -
that's why UML seems to work most times.  Fix this with a simple udelay
implementation.

Signed-off-by: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
Acked-by: Jeff Dike <jdike@addtoit.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 14 insertions, 3 deletions

diff --git a/include/asm-um/delay.h b/include/asm-um/delay.h
index 0985bda6675..c71e32b6741 100644
--- a/include/asm-um/delay.h
+++ b/include/asm-um/delay.h
@@ -1,9 +1,20 @@
 #ifndef __UM_DELAY_H
 #define __UM_DELAY_H
 
-#include "asm/arch/delay.h"
-#include "asm/archparam.h"
-
 #define MILLION 1000000
 
+/* Undefined on purpose */
+extern void __bad_udelay(void);
+
+extern void __udelay(unsigned long usecs);
+extern void __delay(unsigned long loops);
+
+#define udelay(n) ((__builtin_constant_p(n) && (n) > 20000) ? \
+        __bad_udelay() : __udelay(n))
+
+/* It appears that ndelay is not used at all for UML, and has never been
+ * implemented. */
+extern void __unimplemented_ndelay(void);
+#define ndelay(n) __unimplemented_ndelay()
+
 #endif