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authorHendrik Brueckner <brueckner@linux.vnet.ibm.com>2017-10-27 15:45:19 +0200
committerMartin Schwidefsky <schwidefsky@de.ibm.com>2017-11-16 15:06:16 +0100
commitd4c7e649d7bf17792629dbeaf25945e26a32894f (patch)
treef0f9e08bef9a900ad00e1b6c607d29f87017d42c /arch/s390/kernel
parentde9954b75e992d26a67d83990e6219dcb6edc3bf (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.c3
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,