Commit-ID: 4b1b7f8054896cee25669f6cea7cb6dd17f508f7 Gitweb: https://git.kernel.org/tip/4b1b7f8054896cee25669f6cea7cb6dd17f508f7 Author: Pavel Tatashin <pasha.tatas...@oracle.com> AuthorDate: Thu, 19 Jul 2018 16:55:35 -0400 Committer: Thomas Gleixner <t...@linutronix.de> CommitDate: Fri, 20 Jul 2018 00:02:41 +0200
timekeeping: Default boot time offset to local_clock() read_persistent_wall_and_boot_offset() is called during boot to read both the persistent clock and also return the offset between the boot time and the value of persistent clock. Change the default boot_offset from zero to local_clock() so architectures, that do not have a dedicated boot_clock but have early sched_clock(), such as SPARCv9, x86, and possibly more will benefit from this change by getting a better and more consistent estimate of the boot time without need for an arch specific implementation. Signed-off-by: Pavel Tatashin <pasha.tatas...@oracle.com> Signed-off-by: Thomas Gleixner <t...@linutronix.de> Cc: steven.sist...@oracle.com Cc: daniel.m.jor...@oracle.com Cc: li...@armlinux.org.uk Cc: schwidef...@de.ibm.com Cc: heiko.carst...@de.ibm.com Cc: john.stu...@linaro.org Cc: sb...@codeaurora.org Cc: h...@zytor.com Cc: douly.f...@cn.fujitsu.com Cc: pet...@infradead.org Cc: pra...@redhat.com Cc: feng.t...@intel.com Cc: pmla...@suse.com Cc: gno...@lxorguk.ukuu.org.uk Cc: linux-s...@vger.kernel.org Cc: boris.ostrov...@oracle.com Cc: jgr...@suse.com Cc: pbonz...@redhat.com Link: https://lkml.kernel.org/r/20180719205545.16512-17-pasha.tatas...@oracle.com --- kernel/time/timekeeping.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c index cb738f825c12..30d7f64ffc87 100644 --- a/kernel/time/timekeeping.c +++ b/kernel/time/timekeeping.c @@ -1503,14 +1503,17 @@ void __weak read_persistent_clock64(struct timespec64 *ts64) * Weak dummy function for arches that do not yet support it. * wall_time - current time as returned by persistent clock * boot_offset - offset that is defined as wall_time - boot_time - * default to 0. + * The default function calculates offset based on the current value of + * local_clock(). This way architectures that support sched_clock() but don't + * support dedicated boot time clock will provide the best estimate of the + * boot time. */ void __weak __init read_persistent_wall_and_boot_offset(struct timespec64 *wall_time, struct timespec64 *boot_offset) { read_persistent_clock64(wall_time); - *boot_offset = (struct timespec64){0}; + *boot_offset = ns_to_timespec64(local_clock()); } /* Flag for if timekeeping_resume() has injected sleeptime */
