1 files changed, 141 insertions, 32 deletions

diff --git a/kernel/trace/trace_hw_branches.c b/kernel/trace/trace_hw_branches.c
index df21c1e72b9..fff3545fc86 100644
--- a/kernel/trace/trace_hw_branches.c
+++ b/kernel/trace/trace_hw_branches.c
@@ -1,7 +1,8 @@
 /*
  * h/w branch tracer for x86 based on bts
  *
- * Copyright (C) 2008 Markus Metzger <markus.t.metzger@gmail.com>
+ * Copyright (C) 2008-2009 Intel Corporation.
+ * Markus Metzger <markus.t.metzger@gmail.com>, 2008-2009
  *
  */
 
@@ -10,6 +11,9 @@
 #include <linux/debugfs.h>
 #include <linux/ftrace.h>
 #include <linux/kallsyms.h>
+#include <linux/mutex.h>
+#include <linux/cpu.h>
+#include <linux/smp.h>
 
 #include <asm/ds.h>
 
@@ -19,13 +23,32 @@
 
 #define SIZEOF_BTS (1 << 13)
 
+/* The tracer mutex protects the below per-cpu tracer array.
+   It needs to be held to:
+   - start tracing on all cpus
+   - stop tracing on all cpus
+   - start tracing on a single hotplug cpu
+   - stop tracing on a single hotplug cpu
+   - read the trace from all cpus
+   - read the trace from a single cpu
+*/
+static DEFINE_MUTEX(bts_tracer_mutex);
 static DEFINE_PER_CPU(struct bts_tracer *, tracer);
 static DEFINE_PER_CPU(unsigned char[SIZEOF_BTS], 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 struct trace_array *hw_branch_trace __read_mostly;
 
+
+/*
+ * Start tracing on the current cpu.
+ * The argument is ignored.
+ *
+ * pre: bts_tracer_mutex must be locked.
+ */
 static void bts_trace_start_cpu(void *arg)
 {
 	if (this_tracer)
@@ -43,14 +66,20 @@ static void bts_trace_start_cpu(void *arg)
 
 static void bts_trace_start(struct trace_array *tr)
 {
-	int cpu;
+	mutex_lock(&bts_tracer_mutex);
 
-	tracing_reset_online_cpus(tr);
+	on_each_cpu(bts_trace_start_cpu, NULL, 1);
+	trace_hw_branches_enabled = 1;
 
-	for_each_cpu(cpu, cpu_possible_mask)
-		smp_call_function_single(cpu, bts_trace_start_cpu, NULL, 1);
+	mutex_unlock(&bts_tracer_mutex);
 }
 
+/*
+ * Start tracing on the current cpu.
+ * The argument is ignored.
+ *
+ * pre: bts_tracer_mutex must be locked.
+ */
 static void bts_trace_stop_cpu(void *arg)
 {
 	if (this_tracer) {
@@ -61,26 +90,63 @@ static void bts_trace_stop_cpu(void *arg)
 
 static void bts_trace_stop(struct trace_array *tr)
 {
-	int cpu;
+	mutex_lock(&bts_tracer_mutex);
+
+	trace_hw_branches_enabled = 0;
+	on_each_cpu(bts_trace_stop_cpu, NULL, 1);
 
-	for_each_cpu(cpu, cpu_possible_mask)
+	mutex_unlock(&bts_tracer_mutex);
+}
+
+static int __cpuinit bts_hotcpu_handler(struct notifier_block *nfb,
+				     unsigned long action, void *hcpu)
+{
+	unsigned int cpu = (unsigned long)hcpu;
+
+	mutex_lock(&bts_tracer_mutex);
+
+	if (!trace_hw_branches_enabled)
+		goto out;
+
+	switch (action) {
+	case CPU_ONLINE:
+	case CPU_DOWN_FAILED:
+		smp_call_function_single(cpu, bts_trace_start_cpu, NULL, 1);
+		break;
+	case CPU_DOWN_PREPARE:
 		smp_call_function_single(cpu, bts_trace_stop_cpu, NULL, 1);
+		break;
+	}
+
+ out:
+	mutex_unlock(&bts_tracer_mutex);
+	return NOTIFY_DONE;
 }
 
+static struct notifier_block bts_hotcpu_notifier __cpuinitdata = {
+	.notifier_call = bts_hotcpu_handler
+};
+
 static int bts_trace_init(struct trace_array *tr)
 {
+	hw_branch_trace = tr;
+
+	register_hotcpu_notifier(&bts_hotcpu_notifier);
 	tracing_reset_online_cpus(tr);
 	bts_trace_start(tr);
 
 	return 0;
 }
 
+static void bts_trace_reset(struct trace_array *tr)
+{
+	bts_trace_stop(tr);
+	unregister_hotcpu_notifier(&bts_hotcpu_notifier);
+}
+
 static void bts_trace_print_header(struct seq_file *m)
 {
-	seq_puts(m,
-		 "# CPU#        FROM                   TO         FUNCTION\n");
-	seq_puts(m,
-		 "#  |           |                     |             |\n");
+	seq_puts(m, "# CPU#        TO  <-  FROM\n");
 }
 
 static enum print_line_t bts_trace_print_line(struct trace_iterator *iter)
@@ -88,15 +154,15 @@ static enum print_line_t bts_trace_print_line(struct trace_iterator *iter)
 	struct trace_entry *entry = iter->ent;
 	struct trace_seq *seq = &iter->seq;
 	struct hw_branch_entry *it;
+	unsigned long symflags = TRACE_ITER_SYM_OFFSET;
 
 	trace_assign_type(it, entry);
 
 	if (entry->type == TRACE_HW_BRANCHES) {
 		if (trace_seq_printf(seq, "%4d  ", entry->cpu) &&
-		    trace_seq_printf(seq, "0x%016llx -> 0x%016llx ",
-				     it->from, it->to) &&
-		    (!it->from ||
-		     seq_print_ip_sym(seq, it->from, /* sym_flags = */ 0)) &&
+		    seq_print_ip_sym(seq, it->to, symflags) &&
+		    trace_seq_printf(seq, "\t  <-  ") &&
+		    seq_print_ip_sym(seq, it->from, symflags) &&
 		    trace_seq_printf(seq, "\n"))
 			return TRACE_TYPE_HANDLED;
 		return TRACE_TYPE_PARTIAL_LINE;;
@@ -104,26 +170,42 @@ static enum print_line_t bts_trace_print_line(struct trace_iterator *iter)
 	return TRACE_TYPE_UNHANDLED;
 }
 
-void trace_hw_branch(struct trace_array *tr, u64 from, u64 to)
+void trace_hw_branch(u64 from, u64 to)
 {
+	struct trace_array *tr = hw_branch_trace;
 	struct ring_buffer_event *event;
 	struct hw_branch_entry *entry;
-	unsigned long irq;
+	unsigned long irq1, irq2;
+	int cpu;
 
-	event = ring_buffer_lock_reserve(tr->buffer, sizeof(*entry), &irq);
-	if (!event)
+	if (unlikely(!tr))
 		return;
+
+	if (unlikely(!trace_hw_branches_enabled))
+		return;
+
+	local_irq_save(irq1);
+	cpu = raw_smp_processor_id();
+	if (atomic_inc_return(&tr->data[cpu]->disabled) != 1)
+		goto out;
+
+	event = ring_buffer_lock_reserve(tr->buffer, sizeof(*entry), &irq2);
+	if (!event)
+		goto out;
 	entry	= ring_buffer_event_data(event);
 	tracing_generic_entry_update(&entry->ent, 0, from);
 	entry->ent.type = TRACE_HW_BRANCHES;
-	entry->ent.cpu = smp_processor_id();
+	entry->ent.cpu = cpu;
 	entry->from = from;
 	entry->to   = to;
-	ring_buffer_unlock_commit(tr->buffer, event, irq);
+	ring_buffer_unlock_commit(tr->buffer, event, irq2);
+
+ out:
+	atomic_dec(&tr->data[cpu]->disabled);
+	local_irq_restore(irq1);
 }
 
-static void trace_bts_at(struct trace_array *tr,
-			 const struct bts_trace *trace, void *at)
+static void trace_bts_at(const struct bts_trace *trace, void *at)
 {
 	struct bts_struct bts;
 	int err = 0;
@@ -138,18 +220,29 @@ static void trace_bts_at(struct trace_array *tr,
 
 	switch (bts.qualifier) {
 	case BTS_BRANCH:
-		trace_hw_branch(tr, bts.variant.lbr.from, bts.variant.lbr.to);
+		trace_hw_branch(bts.variant.lbr.from, bts.variant.lbr.to);
 		break;
 	}
 }
 
+/*
+ * Collect the trace on the current cpu and write it into the ftrace buffer.
+ *
+ * pre: bts_tracer_mutex must be locked
+ */
 static void trace_bts_cpu(void *arg)
 {
 	struct trace_array *tr = (struct trace_array *) arg;
 	const struct bts_trace *trace;
 	unsigned char *at;
 
-	if (!this_tracer)
+	if (unlikely(!tr))
+		return;
+
+	if (unlikely(atomic_read(&tr->data[raw_smp_processor_id()]->disabled)))
+		return;
+
+	if (unlikely(!this_tracer))
 		return;
 
 	ds_suspend_bts(this_tracer);
@@ -159,11 +252,11 @@ static void trace_bts_cpu(void *arg)
 
 	for (at = trace->ds.top; (void *)at < trace->ds.end;
 	     at += trace->ds.size)
-		trace_bts_at(tr, trace, at);
+		trace_bts_at(trace, at);
 
 	for (at = trace->ds.begin; (void *)at < trace->ds.top;
 	     at += trace->ds.size)
-		trace_bts_at(tr, trace, at);
+		trace_bts_at(trace, at);
 
 out:
 	ds_resume_bts(this_tracer);
@@ -171,22 +264,38 @@ out:
 
 static void trace_bts_prepare(struct trace_iterator *iter)
 {
-	int cpu;
+	mutex_lock(&bts_tracer_mutex);
+
+	on_each_cpu(trace_bts_cpu, iter->tr, 1);
+
+	mutex_unlock(&bts_tracer_mutex);
+}
+
+static void trace_bts_close(struct trace_iterator *iter)
+{
+	tracing_reset_online_cpus(iter->tr);
+}
+
+void trace_hw_branch_oops(void)
+{
+	mutex_lock(&bts_tracer_mutex);
+
+	trace_bts_cpu(hw_branch_trace);
 
-	for_each_cpu(cpu, cpu_possible_mask)
-		smp_call_function_single(cpu, trace_bts_cpu, iter->tr, 1);
+	mutex_unlock(&bts_tracer_mutex);
 }
 
 struct tracer bts_tracer __read_mostly =
 {
 	.name		= "hw-branch-tracer",
 	.init		= bts_trace_init,
-	.reset		= bts_trace_stop,
+	.reset		= bts_trace_reset,
 	.print_header	= bts_trace_print_header,
 	.print_line	= bts_trace_print_line,
 	.start		= bts_trace_start,
 	.stop		= bts_trace_stop,
-	.open		= trace_bts_prepare
+	.open		= trace_bts_prepare,
+	.close		= trace_bts_close
 };
 
 __init static int init_bts_trace(void)