From: Pavel Tatashin <pasha.tatashin@oracle.com>
To: steven.sistare@oracle.com, daniel.m.jordan@oracle.com,
linux@armlinux.org.uk, schwidefsky@de.ibm.com,
heiko.carstens@de.ibm.com, john.stultz@linaro.org,
sboyd@codeaurora.org, x86@kernel.org,
linux-kernel@vger.kernel.org, mingo@redhat.com,
tglx@linutronix.de, hpa@zytor.com, douly.fnst@cn.fujitsu.com,
peterz@infradead.org, prarit@redhat.com, feng.tang@intel.com,
pmladek@suse.com, gnomes@lxorguk.ukuu.org.uk,
linux-s390@vger.kernel.org, pasha.tatashin@oracle.com,
boris.ostrovsky@oracle.com, jgross@suse.com, pbonzini@redhat.com
Subject: [PATCH v15 15/26] time: replace read_boot_clock64() with read_persistent_wall_and_boot_offset()
Date: Thu, 19 Jul 2018 16:55:34 -0400 [thread overview]
Message-ID: <20180719205545.16512-16-pasha.tatashin@oracle.com> (raw)
In-Reply-To: <20180719205545.16512-1-pasha.tatashin@oracle.com>
If architecture does not support exact boot time, it is challenging to
estimate boot time without having a reference to the current persistent
clock value. Yet, it cannot read the persistent clock time again, because
this may lead to math discrepancies with the caller of read_boot_clock64()
who have read the persistent clock at a different time.
This is why it is better to provide two values simultaneously: the
persistent clock value, and the boot time.
Replace read_boot_clock64() with:
read_persistent_wall_and_boot_offset(wall_time, boot_offset)
Where wall_time is returned by read_persistent_clock()
And boot_offset is wall_time - boot time, which defaults to 0.
Signed-off-by: Pavel Tatashin <pasha.tatashin@oracle.com>
---
include/linux/timekeeping.h | 3 +-
kernel/time/timekeeping.c | 59 +++++++++++++++++++------------------
2 files changed, 32 insertions(+), 30 deletions(-)
diff --git a/include/linux/timekeeping.h b/include/linux/timekeeping.h
index 86bc2026efce..686bc27acef0 100644
--- a/include/linux/timekeeping.h
+++ b/include/linux/timekeeping.h
@@ -243,7 +243,8 @@ extern void ktime_get_snapshot(struct system_time_snapshot *systime_snapshot);
extern int persistent_clock_is_local;
extern void read_persistent_clock64(struct timespec64 *ts);
-extern void read_boot_clock64(struct timespec64 *ts);
+void read_persistent_clock_and_boot_offset(struct timespec64 *wall_clock,
+ struct timespec64 *boot_offset);
extern int update_persistent_clock64(struct timespec64 now);
/*
diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index 4786df904c22..cb738f825c12 100644
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -17,6 +17,7 @@
#include <linux/nmi.h>
#include <linux/sched.h>
#include <linux/sched/loadavg.h>
+#include <linux/sched/clock.h>
#include <linux/syscore_ops.h>
#include <linux/clocksource.h>
#include <linux/jiffies.h>
@@ -1496,18 +1497,20 @@ void __weak read_persistent_clock64(struct timespec64 *ts64)
}
/**
- * read_boot_clock64 - Return time of the system start.
+ * read_persistent_wall_and_boot_offset - Read persistent clock, and also offset
+ * from the boot.
*
* Weak dummy function for arches that do not yet support it.
- * Function to read the exact time the system has been started.
- * Returns a timespec64 with tv_sec=0 and tv_nsec=0 if unsupported.
- *
- * XXX - Do be sure to remove it once all arches implement it.
+ * wall_time - current time as returned by persistent clock
+ * boot_offset - offset that is defined as wall_time - boot_time
+ * default to 0.
*/
-void __weak read_boot_clock64(struct timespec64 *ts)
+void __weak __init
+read_persistent_wall_and_boot_offset(struct timespec64 *wall_time,
+ struct timespec64 *boot_offset)
{
- ts->tv_sec = 0;
- ts->tv_nsec = 0;
+ read_persistent_clock64(wall_time);
+ *boot_offset = (struct timespec64){0};
}
/* Flag for if timekeeping_resume() has injected sleeptime */
@@ -1521,28 +1524,29 @@ static bool persistent_clock_exists;
*/
void __init timekeeping_init(void)
{
+ struct timespec64 wall_time, boot_offset, wall_to_mono;
struct timekeeper *tk = &tk_core.timekeeper;
struct clocksource *clock;
unsigned long flags;
- struct timespec64 now, boot, tmp;
-
- read_persistent_clock64(&now);
- if (!timespec64_valid_strict(&now)) {
- pr_warn("WARNING: Persistent clock returned invalid value!\n"
- " Check your CMOS/BIOS settings.\n");
- now.tv_sec = 0;
- now.tv_nsec = 0;
- } else if (now.tv_sec || now.tv_nsec)
- persistent_clock_exists = true;
- read_boot_clock64(&boot);
- if (!timespec64_valid_strict(&boot)) {
- pr_warn("WARNING: Boot clock returned invalid value!\n"
- " Check your CMOS/BIOS settings.\n");
- boot.tv_sec = 0;
- boot.tv_nsec = 0;
+ read_persistent_wall_and_boot_offset(&wall_time, &boot_offset);
+ if (timespec64_valid_strict(&wall_time) &&
+ timespec64_to_ns(&wall_time) > 0) {
+ persistent_clock_exists = true;
+ } else {
+ pr_warn("Persistent clock returned invalid value");
+ wall_time = (struct timespec64){0};
}
+ if (timespec64_compare(&wall_time, &boot_offset) < 0)
+ boot_offset = (struct timespec64){0};
+
+ /*
+ * We want set wall_to_mono, so the following is true:
+ * wall time + wall_to_mono = boot time
+ */
+ wall_to_mono = timespec64_sub(boot_offset, wall_time);
+
raw_spin_lock_irqsave(&timekeeper_lock, flags);
write_seqcount_begin(&tk_core.seq);
ntp_init();
@@ -1552,13 +1556,10 @@ void __init timekeeping_init(void)
clock->enable(clock);
tk_setup_internals(tk, clock);
- tk_set_xtime(tk, &now);
+ tk_set_xtime(tk, &wall_time);
tk->raw_sec = 0;
- if (boot.tv_sec == 0 && boot.tv_nsec == 0)
- boot = tk_xtime(tk);
- set_normalized_timespec64(&tmp, -boot.tv_sec, -boot.tv_nsec);
- tk_set_wall_to_mono(tk, tmp);
+ tk_set_wall_to_mono(tk, wall_to_mono);
timekeeping_update(tk, TK_MIRROR | TK_CLOCK_WAS_SET);
--
2.18.0
next prev parent reply other threads:[~2018-07-19 20:57 UTC|newest]
Thread overview: 76+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-07-19 20:55 [PATCH v15 00/26] Early boot time stamps Pavel Tatashin
2018-07-19 20:55 ` [PATCH v15 01/26] x86/kvmclock: Remove memblock dependency Pavel Tatashin
2018-07-19 22:21 ` [tip:x86/timers] " tip-bot for Pavel Tatashin
2018-07-19 20:55 ` [PATCH v15 02/26] x86/kvmclock: Remove page size requirement from wall_clock Pavel Tatashin
2018-07-19 22:22 ` [tip:x86/timers] " tip-bot for Thomas Gleixner
2018-07-19 20:55 ` [PATCH v15 03/26] x86/kvmclock: Decrapify kvm_register_clock() Pavel Tatashin
2018-07-19 22:23 ` [tip:x86/timers] " tip-bot for Thomas Gleixner
2018-07-19 20:55 ` [PATCH v15 04/26] x86/kvmclock: Cleanup the code Pavel Tatashin
2018-07-19 22:23 ` [tip:x86/timers] " tip-bot for Thomas Gleixner
2018-07-19 20:55 ` [PATCH v15 05/26] x86/kvmclock: Mark variables __initdata and __ro_after_init Pavel Tatashin
2018-07-19 22:24 ` [tip:x86/timers] " tip-bot for Thomas Gleixner
2018-07-19 20:55 ` [PATCH v15 06/26] x86/kvmclock: Move kvmclock vsyscall param and init to kvmclock Pavel Tatashin
2018-07-19 22:24 ` [tip:x86/timers] " tip-bot for Thomas Gleixner
2018-07-19 20:55 ` [PATCH v15 07/26] x86/kvmclock: Switch kvmclock data to a PER_CPU variable Pavel Tatashin
2018-07-19 22:25 ` [tip:x86/timers] " tip-bot for Thomas Gleixner
2018-07-19 20:55 ` [PATCH v15 08/26] x86: text_poke() may access uninitialized struct pages Pavel Tatashin
2018-07-19 22:25 ` [tip:x86/timers] x86/alternatives, jumplabel: Use text_poke_early() before mm_init() tip-bot for Pavel Tatashin
2018-07-19 20:55 ` [PATCH v15 09/26] x86: initialize static branching early Pavel Tatashin
2018-07-19 22:26 ` [tip:x86/timers] x86/jump_label: Initialize " tip-bot for Pavel Tatashin
2018-07-19 20:55 ` [PATCH v15 10/26] x86/CPU: Call detect_nopl() only on the BSP Pavel Tatashin
2018-07-19 22:26 ` [tip:x86/timers] " tip-bot for Borislav Petkov
2018-07-19 20:55 ` [PATCH v15 11/26] x86/tsc: redefine notsc to behave as tsc=unstable Pavel Tatashin
2018-07-19 22:27 ` [tip:x86/timers] x86/tsc: Redefine " tip-bot for Pavel Tatashin
2018-07-19 20:55 ` [PATCH v15 12/26] x86/xen/time: initialize pv xen time in init_hypervisor_platform Pavel Tatashin
2018-07-19 22:27 ` [tip:x86/timers] x86/xen/time: Initialize pv xen time in init_hypervisor_platform() tip-bot for Pavel Tatashin
2018-07-19 20:55 ` [PATCH v15 13/26] x86/xen/time: output xen sched_clock time from 0 Pavel Tatashin
2018-07-19 22:28 ` [tip:x86/timers] x86/xen/time: Output " tip-bot for Pavel Tatashin
2018-07-19 20:55 ` [PATCH v15 14/26] s390/time: add read_persistent_wall_and_boot_offset() Pavel Tatashin
2018-07-19 22:28 ` [tip:x86/timers] s390/time: Add read_persistent_wall_and_boot_offset() tip-bot for Pavel Tatashin
2018-07-19 20:55 ` Pavel Tatashin [this message]
2018-07-19 22:29 ` [tip:x86/timers] timekeeping: Replace read_boot_clock64() with read_persistent_wall_and_boot_offset() tip-bot for Pavel Tatashin
2018-07-19 20:55 ` [PATCH v15 16/26] time: default boot time offset to local_clock() Pavel Tatashin
2018-07-19 22:29 ` [tip:x86/timers] timekeeping: Default " tip-bot for Pavel Tatashin
2018-07-19 20:55 ` [PATCH v15 17/26] s390/time: remove read_boot_clock64() Pavel Tatashin
2018-07-19 22:30 ` [tip:x86/timers] s390/time: Remove read_boot_clock64() tip-bot for Pavel Tatashin
2018-07-19 20:55 ` [PATCH v15 18/26] ARM/time: remove read_boot_clock64() Pavel Tatashin
2018-07-19 22:30 ` [tip:x86/timers] ARM/time: Remove read_boot_clock64() tip-bot for Pavel Tatashin
2018-07-19 20:55 ` [PATCH v15 19/26] x86/tsc: calibrate tsc only once Pavel Tatashin
2018-07-19 22:31 ` [tip:x86/timers] x86/tsc: Calibrate " tip-bot for Pavel Tatashin
2018-07-19 20:55 ` [PATCH v15 20/26] x86/tsc: initialize cyc2ns when tsc freq. is determined Pavel Tatashin
2018-07-19 22:31 ` [tip:x86/timers] x86/tsc: Initialize cyc2ns when tsc frequency " tip-bot for Pavel Tatashin
2018-07-19 20:55 ` [PATCH v15 21/26] x86/tsc: use tsc early Pavel Tatashin
2018-07-19 22:32 ` [tip:x86/timers] x86/tsc: Use TSC as sched clock early tip-bot for Pavel Tatashin
2018-07-19 20:55 ` [PATCH v15 22/26] sched: move sched clock initialization and merge with generic clock Pavel Tatashin
2018-07-19 22:32 ` [tip:x86/timers] sched/clock: Move " tip-bot for Pavel Tatashin
2018-07-19 20:55 ` [PATCH v15 23/26] sched: early boot clock Pavel Tatashin
2018-07-19 22:33 ` [tip:x86/timers] sched/clock: Enable sched clock early tip-bot for Pavel Tatashin
2018-07-24 19:52 ` Guenter Roeck
2018-07-24 20:22 ` Pavel Tatashin
2018-07-25 0:36 ` Pavel Tatashin
2018-07-25 1:24 ` Guenter Roeck
2018-07-25 2:05 ` Pavel Tatashin
2018-07-25 2:41 ` Pavel Tatashin
2018-07-30 12:36 ` Peter Zijlstra
2018-07-30 13:44 ` Pavel Tatashin
2018-07-20 8:09 ` [PATCH v15 23/26] sched: early boot clock Peter Zijlstra
2018-07-20 10:00 ` [tip:x86/timers] sched/clock: Close a hole in sched_clock_init() tip-bot for Peter Zijlstra
2018-11-06 5:42 ` [PATCH v15 23/26] sched: early boot clock Dominique Martinet
2018-11-06 11:35 ` Steven Sistare
2019-01-02 20:20 ` Salvatore Bonaccorso
2019-01-03 21:28 ` Pavel Tatashin
2019-01-03 23:43 ` Dominique Martinet
2019-01-07 18:17 ` Pavel Tatashin
2019-01-07 23:48 ` Dominique Martinet
2019-01-08 1:04 ` Pavel Tatashin
2019-01-08 1:09 ` Dominique Martinet
2019-01-26 2:04 ` Jon DeVree
2019-01-26 16:11 ` Pavel Tatashin
2019-01-04 7:30 ` [PATCH v15 23/26] sched: early boot clock (was Re: Bug#918036: linux: uptime after reboot wrong (kvm-clock related?)) Thorsten Glaser
2018-07-19 20:55 ` [PATCH v15 24/26] sched: use static key for sched_clock_running Pavel Tatashin
2018-07-19 22:33 ` [tip:x86/timers] sched/clock: Use " tip-bot for Pavel Tatashin
2018-07-19 20:55 ` [PATCH v15 25/26] x86/tsc: split native_calibrate_cpu() into early and late parts Pavel Tatashin
2018-07-19 22:34 ` [tip:x86/timers] x86/tsc: Split " tip-bot for Pavel Tatashin
2018-07-19 20:55 ` [PATCH v15 26/26] x86/tsc: use tsc_calibrate_cpu_early and pit_hpet_ptimer_calibrate_cpu Pavel Tatashin
2018-07-19 22:35 ` [tip:x86/timers] x86/tsc: Make use of tsc_calibrate_cpu_early() tip-bot for Pavel Tatashin
2018-07-19 22:34 ` [PATCH v15 00/26] Early boot time stamps Thomas Gleixner
[not found] <154644530361.2390.18185252504260044930.reportbug@ci-busyapps.lan.tarent.de>
[not found] ` <20190102163939.GB13145@eldamar.local>
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=20180719205545.16512-16-pasha.tatashin@oracle.com \
--to=pasha.tatashin@oracle.com \
--cc=boris.ostrovsky@oracle.com \
--cc=daniel.m.jordan@oracle.com \
--cc=douly.fnst@cn.fujitsu.com \
--cc=feng.tang@intel.com \
--cc=gnomes@lxorguk.ukuu.org.uk \
--cc=heiko.carstens@de.ibm.com \
--cc=hpa@zytor.com \
--cc=jgross@suse.com \
--cc=john.stultz@linaro.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-s390@vger.kernel.org \
--cc=linux@armlinux.org.uk \
--cc=mingo@redhat.com \
--cc=pbonzini@redhat.com \
--cc=peterz@infradead.org \
--cc=pmladek@suse.com \
--cc=prarit@redhat.com \
--cc=sboyd@codeaurora.org \
--cc=schwidefsky@de.ibm.com \
--cc=steven.sistare@oracle.com \
--cc=tglx@linutronix.de \
--cc=x86@kernel.org \
/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).