linux-kernel - [PATCH v4 07/13] coresight: perf: traceid: Add perf notifiers for Trace ID

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Message-Id: <20220823091009.14121-8-mike.leach@linaro.org>
Date:   Tue, 23 Aug 2022 10:10:03 +0100
From:   Mike Leach <mike.leach@...aro.org>
To:     coresight@...ts.linaro.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Cc:     mathieu.poirier@...aro.org, suzuki.poulose@....com,
        peterz@...radead.org, mingo@...hat.com, acme@...nel.org,
        linux-perf-users@...r.kernel.org, leo.yan@...aro.org,
        quic_jinlmao@...cinc.com, Mike Leach <mike.leach@...aro.org>
Subject: [PATCH v4 07/13] coresight: perf: traceid: Add perf notifiers for Trace ID

Adds in notifier calls to the trace ID allocator that perf
events are starting and stopping.

This ensures that Trace IDs associated with CPUs remain the same
throughout the perf session, and are only released when all perf
sessions are complete.

Signed-off-by: Mike Leach <mike.leach@...aro.org>
---
 drivers/hwtracing/coresight/coresight-etm-perf.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/drivers/hwtracing/coresight/coresight-etm-perf.c b/drivers/hwtracing/coresight/coresight-etm-perf.c
index 43bbd5dc3d3b..6166f716a6ac 100644
--- a/drivers/hwtracing/coresight/coresight-etm-perf.c
+++ b/drivers/hwtracing/coresight/coresight-etm-perf.c
@@ -22,6 +22,7 @@
 #include "coresight-etm-perf.h"
 #include "coresight-priv.h"
 #include "coresight-syscfg.h"
+#include "coresight-trace-id.h"
 
 static struct pmu etm_pmu;
 static bool etm_perf_up;
@@ -228,8 +229,12 @@ static void free_event_data(struct work_struct *work)
 		if (!(IS_ERR_OR_NULL(*ppath)))
 			coresight_release_path(*ppath);
 		*ppath = NULL;
+		coresight_trace_id_put_cpu_id(cpu);
 	}
 
+	/* mark perf event as done for trace id allocator */
+	coresight_trace_id_perf_stop();
+
 	free_percpu(event_data->path);
 	kfree(event_data);
 }
@@ -300,6 +305,7 @@ static void *etm_setup_aux(struct perf_event *event, void **pages,
 {
 	u32 id, cfg_hash;
 	int cpu = event->cpu;
+	int trace_id;
 	cpumask_t *mask;
 	struct coresight_device *sink = NULL;
 	struct coresight_device *user_sink = NULL, *last_sink = NULL;
@@ -316,6 +322,9 @@ static void *etm_setup_aux(struct perf_event *event, void **pages,
 		sink = user_sink = coresight_get_sink_by_id(id);
 	}
 
+	/* tell the trace ID allocator that a perf event is starting up */
+	coresight_trace_id_perf_start();
+
 	/* check if user wants a coresight configuration selected */
 	cfg_hash = (u32)((event->attr.config2 & GENMASK_ULL(63, 32)) >> 32);
 	if (cfg_hash) {
@@ -388,6 +397,13 @@ static void *etm_setup_aux(struct perf_event *event, void **pages,
 			continue;
 		}
 
+		/* ensure we can allocate a trace ID for this CPU */
+		trace_id = coresight_trace_id_get_cpu_id(cpu);
+		if (!IS_VALID_ID(trace_id)) {
+			cpumask_clear_cpu(cpu, mask);
+			continue;
+		}
+
 		*etm_event_cpu_path_ptr(event_data, cpu) = path;
 	}
 
-- 
2.17.1