[PATCH AUTOSEL 4.4 1/6] sparc: Fix single-pcr perf event counter management.

Sasha Levin
2018-10-30T13:32:24Z

From: "David S. Miller" <davem@davemloft.net>

[ Upstream commit cfdc3170d214046b9509183fe9b9544dc644d40b ]

It is important to clear the hw->state value for non-stopped events
when they are added into the PMU. Otherwise when the event is
scheduled out, we won't read the counter because HES_UPTODATE is still
set. This breaks 'perf stat' and similar use cases, causing all the
events to show zero.

This worked for multi-pcr because we make explicit sparc_pmu_start()
calls in calculate_multiple_pcrs(). calculate_single_pcr() doesn't do
this because the idea there is to accumulate all of the counter
settings into the single pcr value. So we have to add explicit
hw->state handling there.

Like x86, we use the PERF_HES_ARCH bit to track truly stopped events
so that we don't accidently start them on a reload.

Related to all of this, sparc_pmu_start() is missing a userpage update
so add it.

Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
arch/sparc/kernel/perf_event.c | 17 +++++++++++++----
1 file changed, 13 insertions(+), 4 deletions(-)

diff --git a/arch/sparc/kernel/perf_event.c b/arch/sparc/kernel/perf_event.c
index 6596f66ce112..a5d0c2f08110 100644
--- a/arch/sparc/kernel/perf_event.c
+++ b/arch/sparc/kernel/perf_event.c
@@ -926,6 +926,8 @@ static void read_in_all_counters(struct cpu_hw_events *cpuc)
sparc_perf_event_update(cp, &cp->hw,
cpuc->current_idx[i]);
cpuc->current_idx[i] = PIC_NO_INDEX;
+ if (cp->hw.state & PERF_HES_STOPPED)
+ cp->hw.state |= PERF_HES_ARCH;
}
}
}
@@ -958,10 +960,12 @@ static void calculate_single_pcr(struct cpu_hw_events *cpuc)

enc = perf_event_get_enc(cpuc->events[i]);
cpuc->pcr[0] &= ~mask_for_index(idx);
- if (hwc->state & PERF_HES_STOPPED)
+ if (hwc->state & PERF_HES_ARCH) {
cpuc->pcr[0] |= nop_for_index(idx);
- else
+ } else {
cpuc->pcr[0] |= event_encoding(enc, idx);
+ hwc->state = 0;
+ }
}
out:
cpuc->pcr[0] |= cpuc->event[0]->hw.config_base;
@@ -987,6 +991,9 @@ static void calculate_multiple_pcrs(struct cpu_hw_events *cpuc)

cpuc->current_idx[i] = idx;

+ if (cp->hw.state & PERF_HES_ARCH)
+ continue;
+
sparc_pmu_start(cp, PERF_EF_RELOAD);
}
out:
@@ -1078,6 +1085,8 @@ static void sparc_pmu_start(struct perf_event *event, int flags)
event->hw.state = 0;

sparc_pmu_enable_event(cpuc, &event->hw, idx);
+
+ perf_event_update_userpage(event);
}

static void sparc_pmu_stop(struct perf_event *event, int flags)
@@ -1370,9 +1379,9 @@ static int sparc_pmu_add(struct perf_event *event, int ef_flags)
cpuc->events[n0] = event->hw.event_base;
cpuc->current_idx[n0] = PIC_NO_INDEX;

- event->hw.state = PERF_HES_UPTODATE;
+ event->hw.state = PERF_HES_UPTODATE | PERF_HES_STOPPED;
if (!(ef_flags & PERF_EF_START))
- event->hw.state |= PERF_HES_STOPPED;
+ event->hw.state |= PERF_HES_ARCH;

/*
* If group events scheduling transaction was started,
--
2.17.1