From: Anton Blanchard <anton@samba.org>
To: linuxppc-dev@ozlabs.org
Cc: paulus@samba.org
Subject: [PATCH] powerpc: Fix shared processor and mdelay interaction
Date: Sat, 10 Jun 2006 21:25:21 +1000 [thread overview]
Message-ID: <20060610112521.GO23891@krispykreme> (raw)
Paul and Ben found an interaction with mdelay on shared processor where
mdelay can have large errors.
Signed-off-by: Anton Blanchard <anton@samba.org>
---
Index: build/include/asm-powerpc/delay.h
===================================================================
--- build.orig/include/asm-powerpc/delay.h 2006-06-08 10:57:41.000000000 +1000
+++ build/include/asm-powerpc/delay.h 2006-06-10 21:15:02.000000000 +1000
@@ -17,5 +17,18 @@
extern void __delay(unsigned long loops);
extern void udelay(unsigned long usecs);
+/*
+ * On shared processor machines the generic implementation of mdelay can
+ * result in large errors. While each iteration of the loop inside mdelay
+ * is supposed to take 1ms, the hypervisor could sleep our partition for
+ * longer (eg 10ms). With the right timing these errors can add up.
+ *
+ * Since there is no 32bit overflow issue on 64bit kernels, just call
+ * udelay directly.
+ */
+#ifdef CONFIG_PPC64
+#define mdelay(n) udelay((n) * 1000)
+#endif
+
#endif /* __KERNEL__ */
#endif /* _ASM_POWERPC_DELAY_H */
Index: build/include/linux/delay.h
===================================================================
--- build.orig/include/linux/delay.h 2006-06-08 10:57:41.000000000 +1000
+++ build/include/linux/delay.h 2006-06-10 21:04:58.000000000 +1000
@@ -25,10 +25,7 @@ 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
+#ifndef mdelay
#define mdelay(n) (\
(__builtin_constant_p(n) && (n)<=MAX_UDELAY_MS) ? udelay((n)*1000) : \
({unsigned long __ms=(n); while (__ms--) udelay(1000);}))
reply other threads:[~2006-06-10 11:25 UTC|newest]
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