diff options
| 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/vdso32 | |
| parent | 2ace06ec0d997c4332582dbbb8b5e747d22c4400 (diff) | |
| download | lwn-75c7b6f3f6bab0432353caf634598dbdba0d6e74.tar.gz lwn-75c7b6f3f6bab0432353caf634598dbdba0d6e74.zip | |
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/vdso32')
| -rw-r--r-- | arch/s390/kernel/vdso32/clock_gettime.S | 23 | ||||
| -rw-r--r-- | arch/s390/kernel/vdso32/gettimeofday.S | 23 |
2 files changed, 42 insertions, 4 deletions
diff --git a/arch/s390/kernel/vdso32/clock_gettime.S b/arch/s390/kernel/vdso32/clock_gettime.S index 5eec9afbb5b5..a5769b83d90e 100644 --- a/arch/s390/kernel/vdso32/clock_gettime.S +++ b/arch/s390/kernel/vdso32/clock_gettime.S @@ -99,8 +99,27 @@ __kernel_clock_gettime: tml %r4,0x0001 /* pending update ? loop */ jnz 11b stcke 0(%r15) /* Store TOD clock */ - lm %r0,%r1,1(%r15) - s %r0,__VDSO_XTIME_STAMP(%r5) /* TOD - cycle_last */ + lm %r0,%r1,__VDSO_TS_END(%r5) /* TOD steering end time */ + s %r0,1(%r15) /* no - ts_steering_end */ + sl %r1,5(%r15) + brc 3,22f + ahi %r0,-1 +22: ltr %r0,%r0 /* past end of steering? */ + jm 24f + srdl %r0,15 /* 1 per 2^16 */ + tm __VDSO_TS_DIR+3(%r5),0x01 /* steering direction? */ + jz 23f + lcr %r0,%r0 /* negative TOD offset */ + lcr %r1,%r1 + je 23f + ahi %r0,-1 +23: a %r0,1(%r15) /* add TOD timestamp */ + al %r1,5(%r15) + brc 12,25f + ahi %r0,1 + j 25f +24: lm %r0,%r1,1(%r15) /* load TOD timestamp */ +25: s %r0,__VDSO_XTIME_STAMP(%r5) /* TOD - cycle_last */ sl %r1,__VDSO_XTIME_STAMP+4(%r5) brc 3,12f ahi %r0,-1 diff --git a/arch/s390/kernel/vdso32/gettimeofday.S b/arch/s390/kernel/vdso32/gettimeofday.S index 719de6186b20..63b86dceb0bf 100644 --- a/arch/s390/kernel/vdso32/gettimeofday.S +++ b/arch/s390/kernel/vdso32/gettimeofday.S @@ -31,8 +31,27 @@ __kernel_gettimeofday: tml %r4,0x0001 /* pending update ? loop */ jnz 1b stcke 0(%r15) /* Store TOD clock */ - lm %r0,%r1,1(%r15) - s %r0,__VDSO_XTIME_STAMP(%r5) /* TOD - cycle_last */ + lm %r0,%r1,__VDSO_TS_END(%r5) /* TOD steering end time */ + s %r0,1(%r15) + sl %r1,5(%r15) + brc 3,14f + ahi %r0,-1 +14: ltr %r0,%r0 /* past end of steering? */ + jm 16f + srdl %r0,15 /* 1 per 2^16 */ + tm __VDSO_TS_DIR+3(%r5),0x01 /* steering direction? */ + jz 15f + lcr %r0,%r0 /* negative TOD offset */ + lcr %r1,%r1 + je 15f + ahi %r0,-1 +15: a %r0,1(%r15) /* add TOD timestamp */ + al %r1,5(%r15) + brc 12,17f + ahi %r0,1 + j 17f +16: lm %r0,%r1,1(%r15) /* load TOD timestamp */ +17: s %r0,__VDSO_XTIME_STAMP(%r5) /* TOD - cycle_last */ sl %r1,__VDSO_XTIME_STAMP+4(%r5) brc 3,3f ahi %r0,-1 |