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Subject[PATCH v12 2/5] perf: Add a counter for number of user access events in context
Date
For controlling user space counter access, we need to know if any event
in a context (currently scheduled or not) is using user space counters.
Walking the context's list of events would be slow, so add a counter
to track this.

Reviewed-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Rob Herring <robh@kernel.org>
---
v10:
- Re-added.
- Maintain the count in the perf core
v9:
- Dropped
v8:
- new patch
---
include/linux/perf_event.h | 1 +
kernel/events/core.c | 4 ++++
2 files changed, 5 insertions(+)

diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index 34ebcc9af608..d733cac749e2 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -828,6 +828,7 @@ struct perf_event_context {

int nr_events;
int nr_active;
+ int nr_user;
int is_active;
int nr_stat;
int nr_freq;
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 744e8726c5b2..01290d150da3 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -1808,6 +1808,8 @@ list_add_event(struct perf_event *event, struct perf_event_context *ctx)

list_add_rcu(&event->event_entry, &ctx->event_list);
ctx->nr_events++;
+ if (event->hw.flags & PERF_EVENT_FLAG_USER_READ_CNT)
+ ctx->nr_user++;
if (event->attr.inherit_stat)
ctx->nr_stat++;

@@ -1999,6 +2001,8 @@ list_del_event(struct perf_event *event, struct perf_event_context *ctx)
event->attach_state &= ~PERF_ATTACH_CONTEXT;

ctx->nr_events--;
+ if (event->hw.flags & PERF_EVENT_FLAG_USER_READ_CNT)
+ ctx->nr_user--;
if (event->attr.inherit_stat)
ctx->nr_stat--;

--
2.32.0
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