timekeeping: Replace read_boot_clock64() with read_persistent_wall_and_boot_offset()
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> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: steven.sistare@oracle.com Cc: daniel.m.jordan@oracle.com Cc: linux@armlinux.org.uk Cc: schwidefsky@de.ibm.com Cc: heiko.carstens@de.ibm.com Cc: john.stultz@linaro.org Cc: sboyd@codeaurora.org Cc: hpa@zytor.com Cc: douly.fnst@cn.fujitsu.com Cc: peterz@infradead.org Cc: prarit@redhat.com Cc: feng.tang@intel.com Cc: pmladek@suse.com Cc: gnomes@lxorguk.ukuu.org.uk Cc: linux-s390@vger.kernel.org Cc: boris.ostrovsky@oracle.com Cc: jgross@suse.com Cc: pbonzini@redhat.com Link: https://lkml.kernel.org/r/20180719205545.16512-16-pasha.tatashin@oracle.com
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@ -243,7 +243,8 @@ extern void ktime_get_snapshot(struct system_time_snapshot *systime_snapshot);
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extern int persistent_clock_is_local;
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extern int persistent_clock_is_local;
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extern void read_persistent_clock64(struct timespec64 *ts);
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extern void read_persistent_clock64(struct timespec64 *ts);
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extern void read_boot_clock64(struct timespec64 *ts);
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void read_persistent_clock_and_boot_offset(struct timespec64 *wall_clock,
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struct timespec64 *boot_offset);
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extern int update_persistent_clock64(struct timespec64 now);
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extern int update_persistent_clock64(struct timespec64 now);
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/*
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/*
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@ -17,6 +17,7 @@
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#include <linux/nmi.h>
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#include <linux/nmi.h>
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#include <linux/sched.h>
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#include <linux/sched.h>
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#include <linux/sched/loadavg.h>
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#include <linux/sched/loadavg.h>
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#include <linux/sched/clock.h>
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#include <linux/syscore_ops.h>
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#include <linux/syscore_ops.h>
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#include <linux/clocksource.h>
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#include <linux/clocksource.h>
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#include <linux/jiffies.h>
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#include <linux/jiffies.h>
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@ -1496,18 +1497,20 @@ void __weak read_persistent_clock64(struct timespec64 *ts64)
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}
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}
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/**
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/**
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* read_boot_clock64 - Return time of the system start.
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* read_persistent_wall_and_boot_offset - Read persistent clock, and also offset
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* from the boot.
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*
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*
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* Weak dummy function for arches that do not yet support it.
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* Weak dummy function for arches that do not yet support it.
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* Function to read the exact time the system has been started.
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* wall_time - current time as returned by persistent clock
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* Returns a timespec64 with tv_sec=0 and tv_nsec=0 if unsupported.
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* boot_offset - offset that is defined as wall_time - boot_time
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*
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* default to 0.
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* XXX - Do be sure to remove it once all arches implement it.
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*/
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*/
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void __weak read_boot_clock64(struct timespec64 *ts)
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void __weak __init
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read_persistent_wall_and_boot_offset(struct timespec64 *wall_time,
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struct timespec64 *boot_offset)
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{
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{
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ts->tv_sec = 0;
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read_persistent_clock64(wall_time);
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ts->tv_nsec = 0;
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*boot_offset = (struct timespec64){0};
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}
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}
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/* Flag for if timekeeping_resume() has injected sleeptime */
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/* Flag for if timekeeping_resume() has injected sleeptime */
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@ -1521,28 +1524,29 @@ static bool persistent_clock_exists;
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*/
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*/
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void __init timekeeping_init(void)
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void __init timekeeping_init(void)
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{
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{
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struct timespec64 wall_time, boot_offset, wall_to_mono;
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struct timekeeper *tk = &tk_core.timekeeper;
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struct timekeeper *tk = &tk_core.timekeeper;
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struct clocksource *clock;
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struct clocksource *clock;
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unsigned long flags;
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unsigned long flags;
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struct timespec64 now, boot, tmp;
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read_persistent_clock64(&now);
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read_persistent_wall_and_boot_offset(&wall_time, &boot_offset);
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if (!timespec64_valid_strict(&now)) {
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if (timespec64_valid_strict(&wall_time) &&
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pr_warn("WARNING: Persistent clock returned invalid value!\n"
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timespec64_to_ns(&wall_time) > 0) {
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" Check your CMOS/BIOS settings.\n");
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now.tv_sec = 0;
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now.tv_nsec = 0;
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} else if (now.tv_sec || now.tv_nsec)
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persistent_clock_exists = true;
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persistent_clock_exists = true;
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} else {
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read_boot_clock64(&boot);
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pr_warn("Persistent clock returned invalid value");
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if (!timespec64_valid_strict(&boot)) {
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wall_time = (struct timespec64){0};
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pr_warn("WARNING: Boot clock returned invalid value!\n"
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" Check your CMOS/BIOS settings.\n");
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boot.tv_sec = 0;
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boot.tv_nsec = 0;
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}
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}
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if (timespec64_compare(&wall_time, &boot_offset) < 0)
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boot_offset = (struct timespec64){0};
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/*
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* We want set wall_to_mono, so the following is true:
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* wall time + wall_to_mono = boot time
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*/
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wall_to_mono = timespec64_sub(boot_offset, wall_time);
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raw_spin_lock_irqsave(&timekeeper_lock, flags);
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raw_spin_lock_irqsave(&timekeeper_lock, flags);
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write_seqcount_begin(&tk_core.seq);
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write_seqcount_begin(&tk_core.seq);
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ntp_init();
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ntp_init();
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@ -1552,13 +1556,10 @@ void __init timekeeping_init(void)
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clock->enable(clock);
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clock->enable(clock);
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tk_setup_internals(tk, clock);
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tk_setup_internals(tk, clock);
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tk_set_xtime(tk, &now);
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tk_set_xtime(tk, &wall_time);
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tk->raw_sec = 0;
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tk->raw_sec = 0;
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if (boot.tv_sec == 0 && boot.tv_nsec == 0)
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boot = tk_xtime(tk);
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set_normalized_timespec64(&tmp, -boot.tv_sec, -boot.tv_nsec);
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tk_set_wall_to_mono(tk, wall_to_mono);
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tk_set_wall_to_mono(tk, tmp);
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timekeeping_update(tk, TK_MIRROR | TK_CLOCK_WAS_SET);
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timekeeping_update(tk, TK_MIRROR | TK_CLOCK_WAS_SET);
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