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Message-ID: <20090305162921.A25216@sedona.ch.intel.com>
Date: Thu, 5 Mar 2009 16:29:21 +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, srostedt@...hat.com
Subject: [patch 3/4] 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 2009-03-02 16:15:11.000000000 +0100
+++ gits/kernel/trace/trace_hw_branches.c 2009-03-03 10:17:31.000000000 +0100
@@ -38,17 +38,18 @@ static DEFINE_PER_CPU(unsigned char[SIZE
#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);
@@ -63,23 +64,39 @@ static void bts_trace_start_cpu(void *ar
}
}
-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 +104,57 @@ 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 +172,14 @@ 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 +192,6 @@ 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");
@@ -276,7 +328,8 @@ 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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