6.6-stable review patch. If anyone has any objections, please let me know.
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From: Levi Yun yeoreum.yun@arm.com
[ Upstream commit afe5960dc208fe069ddaaeb0994d857b24ac19d1 ]
When a tracepoint event is created with attr.freq = 1, 'hwc->period_left' is not initialized correctly. As a result, in the perf_swevent_overflow() function, when the first time the event occurs, it calculates the event overflow and the perf_swevent_set_period() returns 3, this leads to the event are recorded for three duplicate times.
Step to reproduce: 1. Enable the tracepoint event & starting tracing $ echo 1 > /sys/kernel/tracing/events/module/module_free $ echo 1 > /sys/kernel/tracing/tracing_on
2. Record with perf $ perf record -a --strict-freq -F 1 -e "module:module_free"
3. Trigger module_free event. $ modprobe -i sunrpc $ modprobe -r sunrpc
Result: - Trace pipe result: $ cat trace_pipe modprobe-174509 [003] ..... 6504.868896: module_free: sunrpc
- perf sample: modprobe 174509 [003] 6504.868980: module:module_free: sunrpc modprobe 174509 [003] 6504.868980: module:module_free: sunrpc modprobe 174509 [003] 6504.868980: module:module_free: sunrpc
By setting period_left via perf_swevent_set_period() as other sw_event did, This problem could be solved.
After patch: - Trace pipe result: $ cat trace_pipe modprobe 1153096 [068] 613468.867774: module:module_free: xfs
- perf sample modprobe 1153096 [068] 613468.867794: module:module_free: xfs
Link: https://lore.kernel.org/20240913021347.595330-1-yeoreum.yun@arm.com Fixes: bd2b5b12849a ("perf_counter: More aggressive frequency adjustment") Signed-off-by: Levi Yun yeoreum.yun@arm.com Acked-by: Namhyung Kim namhyung@kernel.org Signed-off-by: Steven Rostedt (Google) rostedt@goodmis.org Signed-off-by: Sasha Levin sashal@kernel.org --- kernel/trace/trace_event_perf.c | 6 ++++++ 1 file changed, 6 insertions(+)
diff --git a/kernel/trace/trace_event_perf.c b/kernel/trace/trace_event_perf.c index 05e7912418126..3ff9caa4a71bb 100644 --- a/kernel/trace/trace_event_perf.c +++ b/kernel/trace/trace_event_perf.c @@ -352,10 +352,16 @@ void perf_uprobe_destroy(struct perf_event *p_event) int perf_trace_add(struct perf_event *p_event, int flags) { struct trace_event_call *tp_event = p_event->tp_event; + struct hw_perf_event *hwc = &p_event->hw;
if (!(flags & PERF_EF_START)) p_event->hw.state = PERF_HES_STOPPED;
+ if (is_sampling_event(p_event)) { + hwc->last_period = hwc->sample_period; + perf_swevent_set_period(p_event); + } + /* * If TRACE_REG_PERF_ADD returns false; no custom action was performed * and we need to take the default action of enqueueing our event on