From 8d4e6c4caa12dafbcba138e5450b7af17b0b2194 Mon Sep 17 00:00:00 2001 From: Alexander Shishkin Date: Thu, 30 Mar 2017 18:39:56 +0300 Subject: perf/core, pt, bts: Get rid of itrace_started I just noticed that hw.itrace_started and hw.config are aliased to the same location. Now, the PT driver happens to use both, which works out fine by sheer luck: - STORE(hw.itrace_start) is ordered before STORE(hw.config), in the program order, although there are no compiler barriers to ensure that, - to the perf_log_itrace_start() hw.itrace_start looks set at the same time as when it is intended to be set because both stores happen in the same path, - hw.config is never reset to zero in the PT driver. Now, the use of hw.config by the PT driver makes more sense (it being a HW PMU) than messing around with itrace_started, which is an awkward API to begin with. This patch replaces hw.itrace_started with an attach_state bit and an API call for the PMU drivers to use to communicate the condition. Signed-off-by: Alexander Shishkin Signed-off-by: Peter Zijlstra (Intel) Cc: Arnaldo Carvalho de Melo Cc: Arnaldo Carvalho de Melo Cc: Jiri Olsa Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Stephane Eranian Cc: Thomas Gleixner Cc: Vince Weaver Cc: vince@deater.net Link: http://lkml.kernel.org/r/20170330153956.25994-1-alexander.shishkin@linux.intel.com Signed-off-by: Ingo Molnar --- kernel/events/core.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) (limited to 'kernel/events') diff --git a/kernel/events/core.c b/kernel/events/core.c index e5467e107624..77fd6b11ef22 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -7301,6 +7301,11 @@ static void perf_log_throttle(struct perf_event *event, int enable) perf_output_end(&handle); } +void perf_event_itrace_started(struct perf_event *event) +{ + event->attach_state |= PERF_ATTACH_ITRACE; +} + static void perf_log_itrace_start(struct perf_event *event) { struct perf_output_handle handle; @@ -7316,7 +7321,7 @@ static void perf_log_itrace_start(struct perf_event *event) event = event->parent; if (!(event->pmu->capabilities & PERF_PMU_CAP_ITRACE) || - event->hw.itrace_started) + event->attach_state & PERF_ATTACH_ITRACE) return; rec.header.type = PERF_RECORD_ITRACE_START; -- cgit v1.2.1