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perf/core: Correct event creation with PERF_FORMAT_GROUP
Andi was asking about PERF_FORMAT_GROUP vs inherited events, which led to the discovery of a bug from commit:3dab77fb1b
("perf: Rework/fix the whole read vs group stuff") - PERF_SAMPLE_GROUP = 1U << 4, + PERF_SAMPLE_READ = 1U << 4, - if (attr->inherit && (attr->sample_type & PERF_SAMPLE_GROUP)) + if (attr->inherit && (attr->read_format & PERF_FORMAT_GROUP)) is a clear fail :/ While this changes user visible behaviour; it was previously possible to create an inherited event with PERF_SAMPLE_READ; this is deemed acceptible because its results were always incorrect. Reported-by: Andi Kleen <ak@linux.intel.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com> Cc: Arnaldo Carvalho de Melo <acme@kernel.org> Cc: Jiri Olsa <jolsa@kernel.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Stephane Eranian <eranian@google.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Vince Weaver <vince@deater.net> Fixes:3dab77fb1b
("perf: Rework/fix the whole read vs group stuff") Link: http://lkml.kernel.org/r/20170530094512.dy2nljns2uq7qa3j@hirez.programming.kicks-ass.net Signed-off-by: Ingo Molnar <mingo@kernel.org>
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commit
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1 changed files with 10 additions and 5 deletions
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@ -5729,9 +5729,6 @@ static void perf_output_read_one(struct perf_output_handle *handle,
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__output_copy(handle, values, n * sizeof(u64));
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}
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/*
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* XXX PERF_FORMAT_GROUP vs inherited events seems difficult.
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*/
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static void perf_output_read_group(struct perf_output_handle *handle,
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struct perf_event *event,
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u64 enabled, u64 running)
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@ -5776,6 +5773,13 @@ static void perf_output_read_group(struct perf_output_handle *handle,
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#define PERF_FORMAT_TOTAL_TIMES (PERF_FORMAT_TOTAL_TIME_ENABLED|\
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PERF_FORMAT_TOTAL_TIME_RUNNING)
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/*
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* XXX PERF_SAMPLE_READ vs inherited events seems difficult.
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*
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* The problem is that its both hard and excessively expensive to iterate the
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* child list, not to mention that its impossible to IPI the children running
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* on another CPU, from interrupt/NMI context.
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*/
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static void perf_output_read(struct perf_output_handle *handle,
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struct perf_event *event)
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{
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@ -9462,9 +9466,10 @@ perf_event_alloc(struct perf_event_attr *attr, int cpu,
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local64_set(&hwc->period_left, hwc->sample_period);
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/*
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* we currently do not support PERF_FORMAT_GROUP on inherited events
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* We currently do not support PERF_SAMPLE_READ on inherited events.
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* See perf_output_read().
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*/
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if (attr->inherit && (attr->read_format & PERF_FORMAT_GROUP))
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if (attr->inherit && (attr->sample_type & PERF_SAMPLE_READ))
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goto err_ns;
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if (!has_branch_stack(event))
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