Commit 8d4e6c4c authored by Alexander Shishkin's avatar Alexander Shishkin Committed by Ingo Molnar

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: default avatarAlexander Shishkin <alexander.shishkin@linux.intel.com>
Signed-off-by: default avatarPeter 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.comSigned-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent e0563e04
......@@ -268,7 +268,7 @@ static void bts_event_start(struct perf_event *event, int flags)
bts->ds_back.bts_absolute_maximum = cpuc->ds->bts_absolute_maximum;
bts->ds_back.bts_interrupt_threshold = cpuc->ds->bts_interrupt_threshold;
event->hw.itrace_started = 1;
perf_event_itrace_started(event);
event->hw.state = 0;
__bts_event_start(event);
......
......@@ -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);
}
......
......@@ -147,9 +147,6 @@ struct hw_perf_event {
struct list_head cqm_groups_entry;
struct list_head cqm_group_entry;
};
struct { /* itrace */
int itrace_started;
};
struct { /* amd_power */
u64 pwr_acc;
u64 ptsc;
......@@ -541,6 +538,7 @@ struct swevent_hlist {
#define PERF_ATTACH_GROUP 0x02
#define PERF_ATTACH_TASK 0x04
#define PERF_ATTACH_TASK_DATA 0x08
#define PERF_ATTACH_ITRACE 0x10
struct perf_cgroup;
struct ring_buffer;
......@@ -864,6 +862,7 @@ extern int perf_aux_output_skip(struct perf_output_handle *handle,
unsigned long size);
extern void *perf_get_aux(struct perf_output_handle *handle);
extern void perf_aux_output_flag(struct perf_output_handle *handle, u64 flags);
extern void perf_event_itrace_started(struct perf_event *event);
extern int perf_pmu_register(struct pmu *pmu, const char *name, int type);
extern void perf_pmu_unregister(struct pmu *pmu);
......
......@@ -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;
......
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