The patch titled
ntp: fix adjtimex() freq return error
has been added to the -mm tree. Its filename is
ntp-fix-adjtimex-freq-return-error.patch
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------------------------------------------------------
Subject: ntp: fix adjtimex() freq return error
From: john stultz <johnstul@xxxxxxxxxx>
Martin Ziegler reported a bug in adjtimex(), where odd positive
frequencies are reduced by 1 while negative values are correct.
See http://bugzilla.kernel.org/show_bug.cgi?id=11370 for details
The issue was introduced in the following commit that increased time_freq
to a 64bit value and increased its resolution:
http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commitdiff;h=074b3b87941c99bc0ce35385b5817924b1ed0c23;hp=eea83d896e318bda54be2d2770d2c5d6668d11db
The problem is how we convert from our internal high res value back to
userland. Instead of dividing, we shift, then mult, then shift again,
causing the slight error seen in the bug.
I don't think adjtimex() is a terribly hot path, so this patch simply uses
div_s64() to convert back to the external resolution and removes the
unused shift defines to resolve the issue.
Signed-off-by: John Stultz <johnstul@xxxxxxxxxx>
Cc: Roman Zippel <zippel@xxxxxxxxxxxxxx>
Reported-by: Martin Ziegler <ziegler@xxxxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: <stable.kernel.org> [2.6.25.x, 2.6.26.x]
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/timex.h | 3 ---
kernel/time/ntp.c | 4 +---
2 files changed, 1 insertion(+), 6 deletions(-)
diff -puN include/linux/timex.h~ntp-fix-adjtimex-freq-return-error include/linux/timex.h
--- a/include/linux/timex.h~ntp-fix-adjtimex-freq-return-error
+++ a/include/linux/timex.h
@@ -82,9 +82,6 @@
*/
#define SHIFT_USEC 16 /* frequency offset scale (shift) */
#define PPM_SCALE (NSEC_PER_USEC << (NTP_SCALE_SHIFT - SHIFT_USEC))
-#define PPM_SCALE_INV_SHIFT 20
-#define PPM_SCALE_INV ((1ll << (PPM_SCALE_INV_SHIFT + NTP_SCALE_SHIFT)) / \
- PPM_SCALE + 1)
#define MAXPHASE 500000000l /* max phase error (ns) */
#define MAXFREQ 500000 /* max frequency error (ns/s) */
diff -puN kernel/time/ntp.c~ntp-fix-adjtimex-freq-return-error kernel/time/ntp.c
--- a/kernel/time/ntp.c~ntp-fix-adjtimex-freq-return-error
+++ a/kernel/time/ntp.c
@@ -402,9 +402,7 @@ int do_adjtimex(struct timex *txc)
if (!(time_status & STA_NANO))
txc->offset /= NSEC_PER_USEC;
}
- txc->freq = shift_right((s32)(time_freq >> PPM_SCALE_INV_SHIFT) *
- (s64)PPM_SCALE_INV,
- NTP_SCALE_SHIFT);
+ txc->freq = div_s64(time_freq, PPM_SCALE);
txc->maxerror = time_maxerror;
txc->esterror = time_esterror;
txc->status = time_status;
_
Patches currently in -mm which might be from johnstul@xxxxxxxxxx are
ntp-fix-adjtimex-freq-return-error.patch
timekeeping-fix-rounding-problem-during-clock-update.patch
ntp-fix-adj_offset_ss_read-bug-and-do_adjtimex-cleanup.patch
clocksource-fix-a-print-format-error-in-the-acpi-pm-clocksource-driver-and-check-range.patch
clocksource-keep-track-of-original-clocksource-frequency.patch
clocksource-introduce-clocksource_forward_now.patch
clocksource-introduce-clock_monotonic_raw.patch
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