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| author | Martin Schwidefsky <schwidefsky@de.ibm.com> | 2016-10-11 12:49:50 +0200 |
|---|---|---|
| committer | Martin Schwidefsky <schwidefsky@de.ibm.com> | 2016-10-28 10:09:02 +0200 |
| commit | 75c7b6f3f6bab0432353caf634598dbdba0d6e74 (patch) | |
| tree | e3f6cd5d3df07a9e9f831759f8270dc3cab481ca /arch/s390/kernel/vdso64/clock_gettime.S | |
| parent | 2ace06ec0d997c4332582dbbb8b5e747d22c4400 (diff) | |
| download | linux-75c7b6f3f6bab0432353caf634598dbdba0d6e74.tar.bz2 | |
s390/time: steer clocksource on STP sync events
On STP sync events the TOD clock will jump in time, either forward or
backward. The TOD clocksource claims to be continuous but in case of
an STP sync with a negative offset it is not.
Subtract the offset injected by the STP sync check from the result of
the TOD clocksource to make it continuous again. Add code to drift the
offset towards zero with a fixed rate, steering 1 second in ~9 hours.
Suggested-by: David Hildenbrand <dahi@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Diffstat (limited to 'arch/s390/kernel/vdso64/clock_gettime.S')
| -rw-r--r-- | arch/s390/kernel/vdso64/clock_gettime.S | 11 |
1 files changed, 10 insertions, 1 deletions
diff --git a/arch/s390/kernel/vdso64/clock_gettime.S b/arch/s390/kernel/vdso64/clock_gettime.S index 61541fb93dc6..9c3b12626dba 100644 --- a/arch/s390/kernel/vdso64/clock_gettime.S +++ b/arch/s390/kernel/vdso64/clock_gettime.S @@ -83,8 +83,17 @@ __kernel_clock_gettime: tmll %r4,0x0001 /* pending update ? loop */ jnz 5b stcke 0(%r15) /* Store TOD clock */ - lgf %r2,__VDSO_TK_SHIFT(%r5) /* Timekeeper shift */ lg %r1,1(%r15) + lg %r0,__VDSO_TS_END(%r5) /* TOD steering end time */ + slgr %r0,%r1 /* now - ts_steering_end */ + ltgr %r0,%r0 /* past end of steering ? */ + jm 17f + srlg %r0,%r0,15 /* 1 per 2^16 */ + tm __VDSO_TS_DIR+3(%r5),0x01 /* steering direction? */ + jz 18f + lcgr %r0,%r0 /* negative TOD offset */ +18: algr %r1,%r0 /* add steering offset */ +17: lgf %r2,__VDSO_TK_SHIFT(%r5) /* Timekeeper shift */ sg %r1,__VDSO_XTIME_STAMP(%r5) /* TOD - cycle_last */ msgf %r1,__VDSO_TK_MULT(%r5) /* * tk->mult */ alg %r1,__VDSO_XTIME_NSEC(%r5) /* + tk->xtime_nsec */ |