Merge tag 'vfio-v4.11-rc1' of git://github.com/awilliam/linux-vfio

[sfrench/cifs-2.6.git] / include / linux / delay.h

diff --git a/include/linux/delay.h b/include/linux/delay.h
index a6ecb34cf547da29ad16edf8b109de2511d10cd5..2ecb3c46b20a2af689b1fcf4a6bea3c8924ded60 100644 (file)
--- a/include/linux/delay.h
+++ b/include/linux/delay.h
@@ -5,6 +5,17 @@
  * Copyright (C) 1993 Linus Torvalds
  *
  * Delay routines, using a pre-computed "loops_per_jiffy" value.
+ *
+ * Please note that ndelay(), udelay() and mdelay() may return early for
+ * several reasons:
+ *  1. computed loops_per_jiffy too low (due to the time taken to
+ *     execute the timer interrupt.)
+ *  2. cache behaviour affecting the time it takes to execute the
+ *     loop function.
+ *  3. CPU clock rate changes.
+ *
+ * Please see this thread:
+ *   http://lists.openwall.net/linux-kernel/2011/01/09/56
  */
 
 #include <linux/kernel.h>