This is a note to let you know that I've just added the patch titled
time: Make sure jiffies_to_msecs() preserves non-zero time periods
to the 4.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
time-make-sure-jiffies_to_msecs-preserves-non-zero-time-periods.patch
and it can be found in the queue-4.9 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From abcbcb80cd09cd40f2089d912764e315459b71f7 Mon Sep 17 00:00:00 2001
From: Geert Uytterhoeven <geert@xxxxxxxxxxxxxx>
Date: Fri, 22 Jun 2018 16:33:57 +0200
Subject: time: Make sure jiffies_to_msecs() preserves non-zero time periods
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From: Geert Uytterhoeven <geert@xxxxxxxxxxxxxx>
commit abcbcb80cd09cd40f2089d912764e315459b71f7 upstream.
For the common cases where 1000 is a multiple of HZ, or HZ is a multiple of
1000, jiffies_to_msecs() never returns zero when passed a non-zero time
period.
However, if HZ > 1000 and not an integer multiple of 1000 (e.g. 1024 or
1200, as used on alpha and DECstation), jiffies_to_msecs() may return zero
for small non-zero time periods. This may break code that relies on
receiving back a non-zero value.
jiffies_to_usecs() does not need such a fix: one jiffy can only be less
than one µs if HZ > 1000000, and such large values of HZ are already
rejected at build time, twice:
- include/linux/jiffies.h does #error if HZ >= 12288,
- kernel/time/time.c has BUILD_BUG_ON(HZ > USEC_PER_SEC).
Broken since forever.
Signed-off-by: Geert Uytterhoeven <geert@xxxxxxxxxxxxxx>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Reviewed-by: Arnd Bergmann <arnd@xxxxxxxx>
Cc: John Stultz <john.stultz@xxxxxxxxxx>
Cc: Stephen Boyd <sboyd@xxxxxxxxxx>
Cc: linux-alpha@xxxxxxxxxxxxxxx
Cc: linux-mips@xxxxxxxxxxxxxx
Cc: stable@xxxxxxxxxxxxxxx
Link: https://lkml.kernel.org/r/20180622143357.7495-1-geert@xxxxxxxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
kernel/time/time.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
--- a/kernel/time/time.c
+++ b/kernel/time/time.c
@@ -28,6 +28,7 @@
*/
#include <linux/export.h>
+#include <linux/kernel.h>
#include <linux/timex.h>
#include <linux/capability.h>
#include <linux/timekeeper_internal.h>
@@ -258,9 +259,10 @@ unsigned int jiffies_to_msecs(const unsi
return (j + (HZ / MSEC_PER_SEC) - 1)/(HZ / MSEC_PER_SEC);
#else
# if BITS_PER_LONG == 32
- return (HZ_TO_MSEC_MUL32 * j) >> HZ_TO_MSEC_SHR32;
+ return (HZ_TO_MSEC_MUL32 * j + (1ULL << HZ_TO_MSEC_SHR32) - 1) >>
+ HZ_TO_MSEC_SHR32;
# else
- return (j * HZ_TO_MSEC_NUM) / HZ_TO_MSEC_DEN;
+ return DIV_ROUND_UP(j * HZ_TO_MSEC_NUM, HZ_TO_MSEC_DEN);
# endif
#endif
}
Patches currently in stable-queue which might be from geert@xxxxxxxxxxxxxx are
queue-4.9/time-make-sure-jiffies_to_msecs-preserves-non-zero-time-periods.patch
queue-4.9/m68k-mm-adjust-vm-area-to-be-unmapped-by-gap-size-for-__iounmap.patch
