diff options
| author | Hendrik Brueckner <brueckner@linux.vnet.ibm.com> | 2017-10-27 15:45:19 +0200 |
|---|---|---|
| committer | Martin Schwidefsky <schwidefsky@de.ibm.com> | 2017-11-16 15:06:16 +0100 |
| commit | d4c7e649d7bf17792629dbeaf25945e26a32894f (patch) | |
| tree | f0f9e08bef9a900ad00e1b6c607d29f87017d42c /arch/s390/kernel | |
| parent | de9954b75e992d26a67d83990e6219dcb6edc3bf (diff) | |
s390/cpum_sf: load program parameter at sampler enablement
The lpp instruction is used to place the PID of the current
task in the program-parameter (PP) register. The register
contents is then included in the sampling data entries.
The lpp instruction loads the PP register only when at least
one sampling function is enabled. Otherwise it is executed
as a no-op.
Linux calls lpp at context switch. If the context switch
happens before the sampler is enabled, the PP register is
empty. That means, the PID of the task that is sampled is
not stored in sampling data until the next context switch.
Hence, always call lpp when enabling the sampler.
Signed-off-by: Hendrik Brueckner <brueckner@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Diffstat (limited to 'arch/s390/kernel')
| -rw-r--r-- | arch/s390/kernel/perf_cpum_sf.c | 3 |
1 files changed, 3 insertions, 0 deletions
diff --git a/arch/s390/kernel/perf_cpum_sf.c b/arch/s390/kernel/perf_cpum_sf.c index 7e9b9e6ee821..dbb62c05805d 100644 --- a/arch/s390/kernel/perf_cpum_sf.c +++ b/arch/s390/kernel/perf_cpum_sf.c @@ -848,6 +848,9 @@ static void cpumsf_pmu_enable(struct pmu *pmu) return; } + /* Load current program parameter */ + lpp(&S390_lowcore.lpp); + debug_sprintf_event(sfdbg, 6, "pmu_enable: es=%i cs=%i ed=%i cd=%i " "tear=%p dear=%p\n", cpuhw->lsctl.es, cpuhw->lsctl.cs, cpuhw->lsctl.ed, cpuhw->lsctl.cd, |