From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: linux-kernel@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
stable@vger.kernel.org, John Stultz <john.stultz@linaro.org>,
Daniel Mentz <danielmentz@google.com>,
Prarit Bhargava <prarit@redhat.com>,
Kevin Brodsky <kevin.brodsky@arm.com>,
Richard Cochran <richardcochran@gmail.com>,
Stephen Boyd <stephen.boyd@linaro.org>,
Will Deacon <will.deacon@arm.com>,
Miroslav Lichvar <mlichvar@redhat.com>,
Thomas Gleixner <tglx@linutronix.de>
Subject: [PATCH 4.9 25/44] time: Fix CLOCK_MONOTONIC_RAW sub-nanosecond accounting
Date: Tue, 27 Jun 2017 16:12:37 +0200 [thread overview]
Message-ID: <20170627141109.754858123@linuxfoundation.org> (raw)
In-Reply-To: <20170627141107.865578528@linuxfoundation.org>
4.9-stable review patch. If anyone has any objections, please let me know.
------------------
From: John Stultz <john.stultz@linaro.org>
commit 3d88d56c5873f6eebe23e05c3da701960146b801 upstream.
Due to how the MONOTONIC_RAW accumulation logic was handled,
there is the potential for a 1ns discontinuity when we do
accumulations. This small discontinuity has for the most part
gone un-noticed, but since ARM64 enabled CLOCK_MONOTONIC_RAW
in their vDSO clock_gettime implementation, we've seen failures
with the inconsistency-check test in kselftest.
This patch addresses the issue by using the same sub-ns
accumulation handling that CLOCK_MONOTONIC uses, which avoids
the issue for in-kernel users.
Since the ARM64 vDSO implementation has its own clock_gettime
calculation logic, this patch reduces the frequency of errors,
but failures are still seen. The ARM64 vDSO will need to be
updated to include the sub-nanosecond xtime_nsec values in its
calculation for this issue to be completely fixed.
Signed-off-by: John Stultz <john.stultz@linaro.org>
Tested-by: Daniel Mentz <danielmentz@google.com>
Cc: Prarit Bhargava <prarit@redhat.com>
Cc: Kevin Brodsky <kevin.brodsky@arm.com>
Cc: Richard Cochran <richardcochran@gmail.com>
Cc: Stephen Boyd <stephen.boyd@linaro.org>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Miroslav Lichvar <mlichvar@redhat.com>
Link: http://lkml.kernel.org/r/1496965462-20003-3-git-send-email-john.stultz@linaro.org
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
include/linux/timekeeper_internal.h | 4 ++--
kernel/time/timekeeping.c | 20 ++++++++++----------
2 files changed, 12 insertions(+), 12 deletions(-)
--- a/include/linux/timekeeper_internal.h
+++ b/include/linux/timekeeper_internal.h
@@ -57,7 +57,7 @@ struct tk_read_base {
* interval.
* @xtime_remainder: Shifted nano seconds left over when rounding
* @cycle_interval
- * @raw_interval: Raw nano seconds accumulated per NTP interval.
+ * @raw_interval: Shifted raw nano seconds accumulated per NTP interval.
* @ntp_error: Difference between accumulated time and NTP time in ntp
* shifted nano seconds.
* @ntp_error_shift: Shift conversion between clock shifted nano seconds and
@@ -99,7 +99,7 @@ struct timekeeper {
cycle_t cycle_interval;
u64 xtime_interval;
s64 xtime_remainder;
- u32 raw_interval;
+ u64 raw_interval;
/* The ntp_tick_length() value currently being used.
* This cached copy ensures we consistently apply the tick
* length for an entire tick, as ntp_tick_length may change
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -278,8 +278,7 @@ static void tk_setup_internals(struct ti
/* Go back from cycles -> shifted ns */
tk->xtime_interval = (u64) interval * clock->mult;
tk->xtime_remainder = ntpinterval - tk->xtime_interval;
- tk->raw_interval =
- ((u64) interval * clock->mult) >> clock->shift;
+ tk->raw_interval = interval * clock->mult;
/* if changing clocks, convert xtime_nsec shift units */
if (old_clock) {
@@ -2023,7 +2022,7 @@ static cycle_t logarithmic_accumulation(
unsigned int *clock_set)
{
cycle_t interval = tk->cycle_interval << shift;
- u64 raw_nsecs;
+ u64 snsec_per_sec;
/* If the offset is smaller than a shifted interval, do nothing */
if (offset < interval)
@@ -2038,14 +2037,15 @@ static cycle_t logarithmic_accumulation(
*clock_set |= accumulate_nsecs_to_secs(tk);
/* Accumulate raw time */
- raw_nsecs = (u64)tk->raw_interval << shift;
- raw_nsecs += tk->raw_time.tv_nsec;
- if (raw_nsecs >= NSEC_PER_SEC) {
- u64 raw_secs = raw_nsecs;
- raw_nsecs = do_div(raw_secs, NSEC_PER_SEC);
- tk->raw_time.tv_sec += raw_secs;
+ tk->tkr_raw.xtime_nsec += (u64)tk->raw_time.tv_nsec << tk->tkr_raw.shift;
+ tk->tkr_raw.xtime_nsec += tk->raw_interval << shift;
+ snsec_per_sec = (u64)NSEC_PER_SEC << tk->tkr_raw.shift;
+ while (tk->tkr_raw.xtime_nsec >= snsec_per_sec) {
+ tk->tkr_raw.xtime_nsec -= snsec_per_sec;
+ tk->raw_time.tv_sec++;
}
- tk->raw_time.tv_nsec = raw_nsecs;
+ tk->raw_time.tv_nsec = tk->tkr_raw.xtime_nsec >> tk->tkr_raw.shift;
+ tk->tkr_raw.xtime_nsec -= (u64)tk->raw_time.tv_nsec << tk->tkr_raw.shift;
/* Accumulate error between NTP and clock interval */
tk->ntp_error += tk->ntp_tick << shift;
next prev parent reply other threads:[~2017-06-27 14:35 UTC|newest]
Thread overview: 45+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-06-27 14:12 [PATCH 4.9 00/44] 4.9.35-stable review Greg Kroah-Hartman
2017-06-27 14:12 ` [PATCH 4.9 01/44] clk: sunxi-ng: a31: Correct lcd1-ch1 clock register offset Greg Kroah-Hartman
2017-06-27 14:12 ` [PATCH 4.9 03/44] xen-blkback: dont leak stack data via response ring Greg Kroah-Hartman
2017-06-27 14:12 ` [PATCH 4.9 04/44] ALSA: firewire-lib: Fix stall of process context at packet error Greg Kroah-Hartman
2017-06-27 14:12 ` [PATCH 4.9 05/44] ALSA: pcm: Dont treat NULL chmap as a fatal error Greg Kroah-Hartman
2017-06-27 14:12 ` [PATCH 4.9 06/44] fs/exec.c: account for argv/envp pointers Greg Kroah-Hartman
2017-06-27 14:12 ` [PATCH 4.9 07/44] powerpc/perf: Fix oops when kthread execs user process Greg Kroah-Hartman
2017-06-27 14:12 ` [PATCH 4.9 08/44] autofs: sanity check status reported with AUTOFS_DEV_IOCTL_FAIL Greg Kroah-Hartman
2017-06-27 14:12 ` [PATCH 4.9 09/44] lib/cmdline.c: fix get_options() overflow while parsing ranges Greg Kroah-Hartman
2017-06-27 14:12 ` [PATCH 4.9 10/44] perf/x86/intel: Add 1G DTLB load/store miss support for SKL Greg Kroah-Hartman
2017-06-27 14:12 ` [PATCH 4.9 11/44] KVM: s390: gaccess: fix real-space designation asce handling for gmap shadows Greg Kroah-Hartman
2017-06-27 14:12 ` [PATCH 4.9 12/44] KVM: PPC: Book3S HV: Preserve userspace HTM state properly Greg Kroah-Hartman
2017-06-27 14:12 ` [PATCH 4.9 13/44] KVM: PPC: Book3S HV: Context-switch EBB registers properly Greg Kroah-Hartman
2017-06-27 14:12 ` [PATCH 4.9 14/44] CIFS: Improve readdir verbosity Greg Kroah-Hartman
2017-06-27 14:12 ` [PATCH 4.9 15/44] cxgb4: notify uP to route ctrlq compl to rdma rspq Greg Kroah-Hartman
2017-06-27 14:12 ` [PATCH 4.9 16/44] HID: Add quirk for Dell PIXART OEM mouse Greg Kroah-Hartman
2017-06-27 14:12 ` [PATCH 4.9 17/44] signal: Only reschedule timers on signals timers have sent Greg Kroah-Hartman
2017-06-27 14:12 ` [PATCH 4.9 18/44] powerpc/kprobes: Pause function_graph tracing during jprobes handling Greg Kroah-Hartman
2017-06-27 14:12 ` [PATCH 4.9 19/44] powerpc/64s: Handle data breakpoints in Radix mode Greg Kroah-Hartman
2017-06-27 14:12 ` [PATCH 4.9 20/44] Input: i8042 - add Fujitsu Lifebook AH544 to notimeout list Greg Kroah-Hartman
2017-06-27 14:12 ` [PATCH 4.9 21/44] brcmfmac: add parameter to pass error code in firmware callback Greg Kroah-Hartman
2017-06-27 14:12 ` [PATCH 4.9 22/44] brcmfmac: use firmware callback upon failure to load Greg Kroah-Hartman
2017-06-27 14:12 ` [PATCH 4.9 23/44] brcmfmac: unbind all devices upon failure in firmware callback Greg Kroah-Hartman
2017-06-27 14:12 ` [PATCH 4.9 24/44] time: Fix clock->read(clock) race around clocksource changes Greg Kroah-Hartman
2017-06-27 14:12 ` Greg Kroah-Hartman [this message]
2017-06-27 14:12 ` [PATCH 4.9 26/44] arm64/vdso: Fix nsec handling for CLOCK_MONOTONIC_RAW Greg Kroah-Hartman
2017-06-27 14:12 ` [PATCH 4.9 27/44] target: Fix kref->refcount underflow in transport_cmd_finish_abort Greg Kroah-Hartman
2017-06-27 14:12 ` [PATCH 4.9 28/44] iscsi-target: Fix delayed logout processing greater than SECONDS_FOR_LOGOUT_COMP Greg Kroah-Hartman
2017-06-27 14:12 ` [PATCH 4.9 29/44] iscsi-target: Reject immediate data underflow larger than SCSI transfer length Greg Kroah-Hartman
2017-06-27 14:12 ` [PATCH 4.9 30/44] drm/radeon: add a PX quirk for another K53TK variant Greg Kroah-Hartman
2017-06-27 14:12 ` [PATCH 4.9 31/44] drm/radeon: add a quirk for Toshiba Satellite L20-183 Greg Kroah-Hartman
2017-06-27 14:12 ` [PATCH 4.9 35/44] of: Add check to of_scan_flat_dt() before accessing initial_boot_params Greg Kroah-Hartman
2017-06-27 14:12 ` [PATCH 4.9 37/44] usb: gadget: f_fs: avoid out of bounds access on comp_desc Greg Kroah-Hartman
2017-06-27 14:12 ` [PATCH 4.9 38/44] rt2x00: avoid introducing a USB dependency in the rt2x00lib module Greg Kroah-Hartman
2017-06-27 14:12 ` [PATCH 4.9 39/44] net: phy: Initialize mdio clock at probe function Greg Kroah-Hartman
2017-06-27 14:12 ` [PATCH 4.9 40/44] dmaengine: bcm2835: Fix cyclic DMA period splitting Greg Kroah-Hartman
2017-06-27 14:12 ` [PATCH 4.9 41/44] spi: double time out tolerance Greg Kroah-Hartman
2017-06-27 14:12 ` [PATCH 4.9 42/44] net: phy: fix marvell phy status reading Greg Kroah-Hartman
2017-06-27 14:12 ` [PATCH 4.9 43/44] jump label: fix passing kbuild_cflags when checking for asm goto support Greg Kroah-Hartman
2017-06-27 14:12 ` [PATCH 4.9 44/44] brcmfmac: fix uninitialized warning in brcmf_usb_probe_phase2() Greg Kroah-Hartman
2017-06-27 17:29 ` [PATCH 4.9 00/44] 4.9.35-stable review Sumit Semwal
2017-06-28 12:03 ` Greg Kroah-Hartman
[not found] ` <59529e31.06d41c0a.2fd63.4a34@mx.google.com>
2017-06-27 18:32 ` Greg Kroah-Hartman
2017-06-27 19:03 ` Guenter Roeck
2017-06-28 13:53 ` Shuah Khan
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20170627141109.754858123@linuxfoundation.org \
--to=gregkh@linuxfoundation.org \
--cc=danielmentz@google.com \
--cc=john.stultz@linaro.org \
--cc=kevin.brodsky@arm.com \
--cc=linux-kernel@vger.kernel.org \
--cc=mlichvar@redhat.com \
--cc=prarit@redhat.com \
--cc=richardcochran@gmail.com \
--cc=stable@vger.kernel.org \
--cc=stephen.boyd@linaro.org \
--cc=tglx@linutronix.de \
--cc=will.deacon@arm.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).