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Date: Fri, 13 Mar 2009 10:48:52 +0100
From: Markus Metzger <markus.t.metzger@...el.com>
To: linux-kernel@...r.kernel.org, mingo@...e.hu, tglx@...utronix.de,
hpa@...or.com
Cc: markus.t.metzger@...el.com, markus.t.metzger@...il.com,
roland@...hat.com, eranian@...glemail.com, oleg@...hat.com,
juan.villacis@...el.com, ak@...ux.jf.intel.com
Subject: [patch 4/5] x86, hw-branch-tracer: keep resources on stop
Distinguish init/reset and start/stop:
init/reset will allocate and release bts tracing resources
stop/start will suspend and resume bts tracing
Return an error on init() if no cpu can be traced.
Signed-off-by: Markus Metzger <markus.t.metzger@...el.com>
---
Index: gits/kernel/trace/trace_hw_branches.c
===================================================================
--- gits.orig/kernel/trace/trace_hw_branches.c 2009-03-09 10:53:20.000000000 +0100
+++ gits/kernel/trace/trace_hw_branches.c 2009-03-09 10:58:41.000000000 +0100
@@ -19,7 +19,7 @@
#include "trace_output.h"
-#define SIZEOF_BTS (1 << 13)
+#define BTS_BUFFER_SIZE (1 << 13)
/*
* The tracer lock protects the below per-cpu tracer array.
@@ -33,53 +33,68 @@
*/
static DEFINE_SPINLOCK(bts_tracer_lock);
static DEFINE_PER_CPU(struct bts_tracer *, tracer);
-static DEFINE_PER_CPU(unsigned char[SIZEOF_BTS], buffer);
+static DEFINE_PER_CPU(unsigned char[BTS_BUFFER_SIZE], buffer);
#define this_tracer per_cpu(tracer, smp_processor_id())
#define this_buffer per_cpu(buffer, smp_processor_id())
-static int __read_mostly trace_hw_branches_enabled;
+static int trace_hw_branches_enabled __read_mostly;
+static int trace_hw_branches_suspended __read_mostly;
static struct trace_array *hw_branch_trace __read_mostly;
/*
- * Start tracing on the current cpu.
+ * Initialize the tracer for the current cpu.
* The argument is ignored.
*
* pre: bts_tracer_lock must be locked.
*/
-static void bts_trace_start_cpu(void *arg)
+static void bts_trace_init_cpu(void *arg)
{
if (this_tracer)
ds_release_bts(this_tracer);
- this_tracer =
- ds_request_bts(/* task = */ NULL, this_buffer, SIZEOF_BTS,
- /* ovfl = */ NULL, /* th = */ (size_t)-1,
- BTS_KERNEL);
+ this_tracer = ds_request_bts(NULL, this_buffer, BTS_BUFFER_SIZE,
+ NULL, (size_t)-1, BTS_KERNEL);
if (IS_ERR(this_tracer)) {
this_tracer = NULL;
return;
}
}
-static void bts_trace_start(struct trace_array *tr)
+static int bts_trace_init(struct trace_array *tr)
{
+ int cpu, avail;
+
spin_lock(&bts_tracer_lock);
- on_each_cpu(bts_trace_start_cpu, NULL, 1);
- trace_hw_branches_enabled = 1;
+ hw_branch_trace = tr;
+
+ on_each_cpu(bts_trace_init_cpu, NULL, 1);
+
+ /* Check on how many cpus we could enable tracing */
+ avail = 0;
+ for_each_online_cpu(cpu)
+ if (per_cpu(tracer, cpu))
+ avail++;
+
+ trace_hw_branches_enabled = (avail ? 1 : 0);
+ trace_hw_branches_suspended = 0;
spin_unlock(&bts_tracer_lock);
+
+
+ /* If we could not enable tracing on a single cpu, we fail. */
+ return avail ? 0 : -EOPNOTSUPP;
}
/*
- * Stop tracing on the current cpu.
+ * Release the tracer for the current cpu.
* The argument is ignored.
*
* pre: bts_tracer_lock must be locked.
*/
-static void bts_trace_stop_cpu(void *arg)
+static void bts_trace_release_cpu(void *arg)
{
if (this_tracer) {
ds_release_bts(this_tracer);
@@ -87,12 +102,57 @@ static void bts_trace_stop_cpu(void *arg
}
}
-static void bts_trace_stop(struct trace_array *tr)
+static void bts_trace_reset(struct trace_array *tr)
{
spin_lock(&bts_tracer_lock);
+ on_each_cpu(bts_trace_release_cpu, NULL, 1);
trace_hw_branches_enabled = 0;
- on_each_cpu(bts_trace_stop_cpu, NULL, 1);
+ trace_hw_branches_suspended = 0;
+
+ spin_unlock(&bts_tracer_lock);
+}
+
+/*
+ * Resume tracing on the current cpu.
+ * The argument is ignored.
+ *
+ * pre: bts_tracer_lock must be locked.
+ */
+static void bts_trace_resume_cpu(void *arg)
+{
+ if (this_tracer)
+ ds_resume_bts(this_tracer);
+}
+
+static void bts_trace_start(struct trace_array *tr)
+{
+ spin_lock(&bts_tracer_lock);
+
+ on_each_cpu(bts_trace_resume_cpu, NULL, 1);
+ trace_hw_branches_suspended = 0;
+
+ spin_unlock(&bts_tracer_lock);
+}
+
+/*
+ * Suspend tracing on the current cpu.
+ * The argument is ignored.
+ *
+ * pre: bts_tracer_lock must be locked.
+ */
+static void bts_trace_suspend_cpu(void *arg)
+{
+ if (this_tracer)
+ ds_suspend_bts(this_tracer);
+}
+
+static void bts_trace_stop(struct trace_array *tr)
+{
+ spin_lock(&bts_tracer_lock);
+
+ on_each_cpu(bts_trace_suspend_cpu, NULL, 1);
+ trace_hw_branches_suspended = 1;
spin_unlock(&bts_tracer_lock);
}
@@ -110,10 +170,14 @@ static int __cpuinit bts_hotcpu_handler(
switch (action) {
case CPU_ONLINE:
case CPU_DOWN_FAILED:
- smp_call_function_single(cpu, bts_trace_start_cpu, NULL, 1);
+ smp_call_function_single(cpu, bts_trace_init_cpu, NULL, 1);
+
+ if (trace_hw_branches_suspended)
+ smp_call_function_single(cpu, bts_trace_suspend_cpu,
+ NULL, 1);
break;
case CPU_DOWN_PREPARE:
- smp_call_function_single(cpu, bts_trace_stop_cpu, NULL, 1);
+ smp_call_function_single(cpu, bts_trace_release_cpu, NULL, 1);
break;
}
@@ -126,20 +190,6 @@ static struct notifier_block bts_hotcpu_
.notifier_call = bts_hotcpu_handler
};
-static int bts_trace_init(struct trace_array *tr)
-{
- hw_branch_trace = tr;
-
- bts_trace_start(tr);
-
- return 0;
-}
-
-static void bts_trace_reset(struct trace_array *tr)
-{
- bts_trace_stop(tr);
-}
-
static void bts_trace_print_header(struct seq_file *m)
{
seq_puts(m, "# CPU# TO <- FROM\n");
@@ -228,7 +278,7 @@ static void trace_bts_at(const struct bt
*/
static void trace_bts_cpu(void *arg)
{
- struct trace_array *tr = (struct trace_array *) arg;
+ struct trace_array *tr = (struct trace_array *)arg;
const struct bts_trace *trace;
unsigned char *at;
@@ -276,7 +326,8 @@ void trace_hw_branch_oops(void)
{
spin_lock(&bts_tracer_lock);
- trace_bts_cpu(hw_branch_trace);
+ if (trace_hw_branches_enabled)
+ trace_bts_cpu(hw_branch_trace);
spin_unlock(&bts_tracer_lock);
}
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