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| author | Pavel Tatashin <pasha.tatashin@oracle.com> | 2018-07-19 23:55:34 +0300 |
|---|---|---|
| committer | Thomas Gleixner <tglx@linutronix.de> | 2018-07-20 01:02:40 +0300 |
| commit | 3eca993740b8eb40f514b90b1877a4dbcf0a6710 (patch) | |
| tree | a34720fb82704a1258c84ae0d8255091d36310f7 /include/linux/timekeeping.h | |
| parent | be2e0e4257678408b0ab00ea9e743b9094e393e8 (diff) | |
| download | linux-3eca993740b8eb40f514b90b1877a4dbcf0a6710.tar.xz | |
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
Diffstat (limited to 'include/linux/timekeeping.h')
| -rw-r--r-- | include/linux/timekeeping.h | 3 |
1 files changed, 2 insertions, 1 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); /* |