From: Arjan van de Ven <arjanv@redhat.com>
Calling mdelay() from hardirq handlers is a very very nasty thing to do;
for one it destroys our irq latency story but it also potentially does foul
things to timekeeping now that HZ=1000. Patch below makes mdelay() warn
(once per caller) if it's called from irq context. It removes the
"optimisation" for constant mdelay but I don't think anyone cares about
saving 2 cpu cycles in calling mdelay really.
---
25-akpm/include/linux/delay.h | 17 ++++++++---------
1 files changed, 8 insertions(+), 9 deletions(-)
diff -puN include/linux/delay.h~warn-on-mdelay-in-irq-handlers include/linux/delay.h
--- 25/include/linux/delay.h~warn-on-mdelay-in-irq-handlers Wed Mar 24 14:03:01 2004
+++ 25-akpm/include/linux/delay.h Wed Mar 24 14:03:01 2004
@@ -10,7 +10,7 @@
extern unsigned long loops_per_jiffy;
#include <asm/delay.h>
-
+#include <asm/hardirq.h>
/*
* Using udelay() for intervals greater than a few milliseconds can
* risk overflow for high loops_per_jiffy (high bogomips) machines. The
@@ -25,14 +25,13 @@ extern unsigned long loops_per_jiffy;
#define MAX_UDELAY_MS 5
#endif
-#ifdef notdef
-#define mdelay(n) (\
- {unsigned long __ms=(n); while (__ms--) udelay(1000);})
-#else
-#define mdelay(n) (\
- (__builtin_constant_p(n) && (n)<=MAX_UDELAY_MS) ? udelay((n)*1000) : \
- ({unsigned long __ms=(n); while (__ms--) udelay(1000);}))
-#endif
+#define mdelay(n) ( \
+ { \
+ static int warned=0; \
+ unsigned long __ms=(n); \
+ WARN_ON(in_irq() && !(warned++)); \
+ while (__ms--) udelay(1000); \
+ })
#ifndef ndelay
#define ndelay(x) udelay(((x)+999)/1000)
_