x86, ftrace, hw-branch-tracer: dump trace on oops

Dump the branch trace on an oops (based on ftrace_dump_on_oops).

Signed-off-by: Markus Metzger <markus.t.metzger@intel.com>
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 22 insertions, 7 deletions

diff --git a/kernel/trace/trace_hw_branches.c b/kernel/trace/trace_hw_branches.c
index 398195397c75..e56df2c7d679 100644
--- a/kernel/trace/trace_hw_branches.c
+++ b/kernel/trace/trace_hw_branches.c
@@ -40,6 +40,7 @@ static DEFINE_PER_CPU(unsigned char[SIZEOF_BTS], buffer);
 #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;
 
 
 /*
@@ -128,6 +129,8 @@ static struct notifier_block bts_hotcpu_notifier __cpuinitdata = {
 
 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);
@@ -170,8 +173,9 @@ 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 irq1, irq2;
@@ -204,8 +208,7 @@ void trace_hw_branch(struct trace_array *tr, u64 from, u64 to)
         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;
@@ -220,7 +223,7 @@ 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;
         }
 }
@@ -236,12 +239,15 @@ static void trace_bts_cpu(void *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);
         trace = ds_read_bts(this_tracer);
         if (!trace)
@@ -249,11 +255,11 @@ 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);
@@ -268,6 +274,15 @@ static void trace_bts_prepare(struct trace_iterator *iter)
         mutex_unlock(&bts_tracer_mutex);
 }
 
+void trace_hw_branch_oops(void)
+{
+        mutex_lock(&bts_tracer_mutex);
+
+        trace_bts_cpu(hw_branch_trace);
+
+        mutex_unlock(&bts_tracer_mutex);
+}
+
 struct tracer bts_tracer __read_mostly =
 {
         .name           = "hw-branch-tracer",