diff options
author | Alexander Shishkin <alexander.shishkin@linux.intel.com> | 2017-03-30 18:39:56 +0300 |
---|---|---|
committer | Ingo Molnar <mingo@kernel.org> | 2017-08-29 16:09:24 +0300 |
commit | 8d4e6c4caa12dafbcba138e5450b7af17b0b2194 (patch) | |
tree | a9b6c4f3076bd27f9a87fb67a2907c9a0a3c5cbd /arch/x86/events/intel/pt.c | |
parent | e0563e049531973e665db853e825a4efed9f881d (diff) | |
download | linux-8d4e6c4caa12dafbcba138e5450b7af17b0b2194.tar.xz |
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 <alexander.shishkin@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Arnaldo Carvalho de Melo <acme@infradead.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
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 <vincent.weaver@maine.edu>
Cc: vince@deater.net
Link: http://lkml.kernel.org/r/20170330153956.25994-1-alexander.shishkin@linux.intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'arch/x86/events/intel/pt.c')
-rw-r--r-- | arch/x86/events/intel/pt.c | 5 |
1 files changed, 3 insertions, 2 deletions
diff --git a/arch/x86/events/intel/pt.c b/arch/x86/events/intel/pt.c index ae8324d65e61..81fd41d5a0d9 100644 --- a/arch/x86/events/intel/pt.c +++ b/arch/x86/events/intel/pt.c @@ -471,8 +471,9 @@ static void pt_config(struct perf_event *event) struct pt *pt = this_cpu_ptr(&pt_ctx); u64 reg; - if (!event->hw.itrace_started) { - event->hw.itrace_started = 1; + /* First round: clear STATUS, in particular the PSB byte counter. */ + if (!event->hw.config) { + perf_event_itrace_started(event); wrmsrl(MSR_IA32_RTIT_STATUS, 0); } |