1 files changed, 146 insertions, 39 deletions

diff --git a/kernel/trace/trace_hw_branches.c b/kernel/trace/trace_hw_branches.c
index 649df22d435f..7bfdf4c2347f 100644
--- a/kernel/trace/trace_hw_branches.c
+++ b/kernel/trace/trace_hw_branches.c
@@ -1,30 +1,53 @@
 /*
  * 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
  */
-
-#include <linux/module.h>
-#include <linux/fs.h>
+#include <linux/spinlock.h>
+#include <linux/kallsyms.h>
 #include <linux/debugfs.h>
 #include <linux/ftrace.h>
-#include <linux/kallsyms.h>
+#include <linux/module.h>
+#include <linux/cpu.h>
+#include <linux/smp.h>
+#include <linux/fs.h>
 
 #include <asm/ds.h>
 
 #include "trace.h"
+#include "trace_output.h"
 
 
 #define SIZEOF_BTS (1 << 13)
 
+/*
+ * The tracer lock 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_SPINLOCK(bts_tracer_lock);
 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_lock must be locked.
+ */
 static void bts_trace_start_cpu(void *arg)
 {
         if (this_tracer)
@@ -42,14 +65,20 @@ static void bts_trace_start_cpu(void *arg)
 
 static void bts_trace_start(struct trace_array *tr)
 {
-        int cpu;
+        spin_lock(&bts_tracer_lock);
 
-        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);
+        spin_unlock(&bts_tracer_lock);
 }
 
+/*
+ * Stop tracing on the current cpu.
+ * The argument is ignored.
+ *
+ * pre: bts_tracer_lock must be locked.
+ */
 static void bts_trace_stop_cpu(void *arg)
 {
         if (this_tracer) {
@@ -60,26 +89,60 @@ static void bts_trace_stop_cpu(void *arg)
 
 static void bts_trace_stop(struct trace_array *tr)
 {
-        int cpu;
+        spin_lock(&bts_tracer_lock);
+
+        trace_hw_branches_enabled = 0;
+        on_each_cpu(bts_trace_stop_cpu, NULL, 1);
+
+        spin_unlock(&bts_tracer_lock);
+}
+
+static int __cpuinit bts_hotcpu_handler(struct notifier_block *nfb,
+                                     unsigned long action, void *hcpu)
+{
+        unsigned int cpu = (unsigned long)hcpu;
 
-        for_each_cpu(cpu, cpu_possible_mask)
+        spin_lock(&bts_tracer_lock);
+
+        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:
+        spin_unlock(&bts_tracer_lock);
+        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)
 {
-        tracing_reset_online_cpus(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#        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)
@@ -87,15 +150,15 @@ 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)) &&
+                if (trace_seq_printf(seq, "%4d  ", iter->cpu) &&
+                    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;;
@@ -103,26 +166,42 @@ 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;
+        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 = trace_buffer_lock_reserve(tr, TRACE_HW_BRANCHES,
+                                          sizeof(*entry), 0, 0);
+        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->from = from;
         entry->to   = to;
-        ring_buffer_unlock_commit(tr->buffer, event, irq);
+        trace_buffer_unlock_commit(tr, event, 0, 0);
+
+ 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;
@@ -137,18 +216,29 @@ 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_lock 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);
@@ -158,11 +248,11 @@ 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);
@@ -170,26 +260,43 @@ out:
 
 static void trace_bts_prepare(struct trace_iterator *iter)
 {
-        int cpu;
+        spin_lock(&bts_tracer_lock);
+
+        on_each_cpu(trace_bts_cpu, iter->tr, 1);
+
+        spin_unlock(&bts_tracer_lock);
+}
+
+static void trace_bts_close(struct trace_iterator *iter)
+{
+        tracing_reset_online_cpus(iter->tr);
+}
+
+void trace_hw_branch_oops(void)
+{
+        spin_lock(&bts_tracer_lock);
+
+        trace_bts_cpu(hw_branch_trace);
 
-        for_each_cpu(cpu, cpu_possible_mask)
-                smp_call_function_single(cpu, trace_bts_cpu, iter->tr, 1);
+        spin_unlock(&bts_tracer_lock);
 }
 
 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)
 {
+        register_hotcpu_notifier(&bts_hotcpu_notifier);
         return register_tracer(&bts_tracer);
 }
 device_initcall(init_bts_trace);