s390/cpum_sf: Do not re-enable event after deletion

Event delete removes an event from the event list, but common
code invokes the PMU's enable function later on. This happens
in event_sched_out() and leads to the following call sequence:

  event_sched_out()
  +--> cpumsf_pmu_del()
  +--> cpumsf_pmu_enable()

In cpumsf_pmu_enable() return immediately when the event is not
active. Also remove an unneeded if clause. That if() statement
is only reached when flag PMU_F_IN_USE has been set in
cpumsf_pmu_add(). And this function also sets cpuhw->event
to a valid value.

Remove WARN_ON_ONCE() statement which never triggered.

Signed-off-by: Thomas Richter <tmricht@linux.ibm.com>
Reviewed-by: Hendrik Brueckner <brueckner@linux.ibm.com>
Acked-by: Sumanth Korikkar <sumanthk@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>

diff --git a/arch/s390/kernel/perf_cpum_sf.c b/arch/s390/kernel/perf_cpum_sf.c
index e806693c8473d54a1dcd82b11f576324403ef239..c916d04815db0123bbf079b51d5b221e66f76c56 100644 (file)
--- a/arch/s390/kernel/perf_cpum_sf.c
+++ b/arch/s390/kernel/perf_cpum_sf.c
@@ -910,10 +910,14 @@ static void cpumsf_pmu_enable(struct pmu *pmu)
        struct hw_perf_event *hwc;
        int err;
 
-       if (cpuhw->flags & PMU_F_ENABLED)
-               return;
-
-       if (cpuhw->flags & PMU_F_ERR_MASK)
+       /*
+        * Event must be
+        * - added/started on this CPU (PMU_F_IN_USE set)
+        * - and CPU must be available (PMU_F_RESERVED set)
+        * - and not already enabled (PMU_F_ENABLED not set)
+        * - and not in error condition (PMU_F_ERR_MASK not set)
+        */
+       if (cpuhw->flags != (PMU_F_IN_USE | PMU_F_RESERVED))
                return;
 
        /* Check whether to extent the sampling buffer.
@@ -927,19 +931,16 @@ static void cpumsf_pmu_enable(struct pmu *pmu)
         * facility, but it can be fully re-enabled using sampling controls that
         * have been saved in cpumsf_pmu_disable().
         */
-       if (cpuhw->event) {
-               hwc = &cpuhw->event->hw;
-               if (!(SAMPL_DIAG_MODE(hwc))) {
-                       /*
-                        * Account number of overflow-designated
-                        * buffer extents
-                        */
-                       sfb_account_overflows(cpuhw, hwc);
-                       extend_sampling_buffer(&cpuhw->sfb, hwc);
-               }
-               /* Rate may be adjusted with ioctl() */
-               cpuhw->lsctl.interval = SAMPL_RATE(hwc);
+       hwc = &cpuhw->event->hw;
+       if (!(SAMPL_DIAG_MODE(hwc))) {
+               /*
+                * Account number of overflow-designated buffer extents
+                */
+               sfb_account_overflows(cpuhw, hwc);
+               extend_sampling_buffer(&cpuhw->sfb, hwc);
        }
+       /* Rate may be adjusted with ioctl() */
+       cpuhw->lsctl.interval = SAMPL_RATE(hwc);
 
        /* (Re)enable the PMU and sampling facility */
        err = lsctl(&cpuhw->lsctl);
@@ -1954,13 +1955,12 @@ static void cpumf_measurement_alert(struct ext_code ext_code,
 
        /* Program alert request */
        if (alert & CPU_MF_INT_SF_PRA) {
-               if (cpuhw->flags & PMU_F_IN_USE)
+               if (cpuhw->flags & PMU_F_IN_USE) {
                        if (SAMPL_DIAG_MODE(&cpuhw->event->hw))
                                hw_collect_aux(cpuhw);
                        else
                                hw_perf_event_update(cpuhw->event, 0);
-               else
-                       WARN_ON_ONCE(!(cpuhw->flags & PMU_F_IN_USE));
+               }
        }
 
        /* Report measurement alerts only for non-PRA codes */