Merge branch 'tracing/hw-branch-tracing' into tracing/core

Merge reason: this topic is ready for upstream now. It passed
              Oleg's review and Andrew had no further mm/*
              objections/observations either.

Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 102 insertions, 97 deletions

diff --git a/kernel/trace/trace_hw_branches.c b/kernel/trace/trace_hw_branches.c
index 8683d50a753a..ca7d7c4d0c2a 100644
--- a/kernel/trace/trace_hw_branches.c
+++ b/kernel/trace/trace_hw_branches.c
@@ -1,10 +1,9 @@
 /*
- * h/w branch tracer for x86 based on bts
+ * h/w branch tracer for x86 based on BTS
  *
  * Copyright (C) 2008-2009 Intel Corporation.
  * Markus Metzger <markus.t.metzger@gmail.com>, 2008-2009
  */
-#include <linux/spinlock.h>
 #include <linux/kallsyms.h>
 #include <linux/debugfs.h>
 #include <linux/ftrace.h>
@@ -15,110 +14,119 @@
 
 #include <asm/ds.h>
 
-#include "trace.h"
 #include "trace_output.h"
+#include "trace.h"
 
 
-#define SIZEOF_BTS (1 << 13)
+#define BTS_BUFFER_SIZE (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);
+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.
- * 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(int cpu)
 {
-        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);
-        if (IS_ERR(this_tracer)) {
-                this_tracer = NULL;
-                return;
-        }
+        per_cpu(tracer, cpu) =
+                ds_request_bts_cpu(cpu, per_cpu(buffer, cpu), BTS_BUFFER_SIZE,
+                                   NULL, (size_t)-1, BTS_KERNEL);
+
+        if (IS_ERR(per_cpu(tracer, cpu)))
+                per_cpu(tracer, cpu) = NULL;
 }
 
-static void bts_trace_start(struct trace_array *tr)
+static int bts_trace_init(struct trace_array *tr)
 {
-        spin_lock(&bts_tracer_lock);
+        int cpu;
+
+        hw_branch_trace = tr;
+        trace_hw_branches_enabled = 0;
 
-        on_each_cpu(bts_trace_start_cpu, NULL, 1);
-        trace_hw_branches_enabled = 1;
+        get_online_cpus();
+        for_each_online_cpu(cpu) {
+                bts_trace_init_cpu(cpu);
 
-        spin_unlock(&bts_tracer_lock);
+                if (likely(per_cpu(tracer, cpu)))
+                        trace_hw_branches_enabled = 1;
+        }
+        trace_hw_branches_suspended = 0;
+        put_online_cpus();
+
+        /* If we could not enable tracing on a single cpu, we fail. */
+        return trace_hw_branches_enabled ? 0 : -EOPNOTSUPP;
 }
 
-/*
- * 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)
+static void bts_trace_reset(struct trace_array *tr)
 {
-        if (this_tracer) {
-                ds_release_bts(this_tracer);
-                this_tracer = NULL;
+        int cpu;
+
+        get_online_cpus();
+        for_each_online_cpu(cpu) {
+                if (likely(per_cpu(tracer, cpu))) {
+                        ds_release_bts(per_cpu(tracer, cpu));
+                        per_cpu(tracer, cpu) = NULL;
+                }
         }
+        trace_hw_branches_enabled = 0;
+        trace_hw_branches_suspended = 0;
+        put_online_cpus();
 }
 
-static void bts_trace_stop(struct trace_array *tr)
+static void bts_trace_start(struct trace_array *tr)
 {
-        spin_lock(&bts_tracer_lock);
+        int cpu;
 
-        trace_hw_branches_enabled = 0;
-        on_each_cpu(bts_trace_stop_cpu, NULL, 1);
+        get_online_cpus();
+        for_each_online_cpu(cpu)
+                if (likely(per_cpu(tracer, cpu)))
+                        ds_resume_bts(per_cpu(tracer, cpu));
+        trace_hw_branches_suspended = 0;
+        put_online_cpus();
+}
 
-        spin_unlock(&bts_tracer_lock);
+static void bts_trace_stop(struct trace_array *tr)
+{
+        int cpu;
+
+        get_online_cpus();
+        for_each_online_cpu(cpu)
+                if (likely(per_cpu(tracer, cpu)))
+                        ds_suspend_bts(per_cpu(tracer, cpu));
+        trace_hw_branches_suspended = 1;
+        put_online_cpus();
 }
 
 static int __cpuinit bts_hotcpu_handler(struct notifier_block *nfb,
                                      unsigned long action, void *hcpu)
 {
-        unsigned int cpu = (unsigned long)hcpu;
-
-        spin_lock(&bts_tracer_lock);
-
-        if (!trace_hw_branches_enabled)
-                goto out;
+        int cpu = (long)hcpu;
 
         switch (action) {
         case CPU_ONLINE:
         case CPU_DOWN_FAILED:
-                smp_call_function_single(cpu, bts_trace_start_cpu, NULL, 1);
+                /* The notification is sent with interrupts enabled. */
+                if (trace_hw_branches_enabled) {
+                        bts_trace_init_cpu(cpu);
+
+                        if (trace_hw_branches_suspended &&
+                            likely(per_cpu(tracer, cpu)))
+                                ds_suspend_bts(per_cpu(tracer, cpu));
+                }
                 break;
+
         case CPU_DOWN_PREPARE:
-                smp_call_function_single(cpu, bts_trace_stop_cpu, NULL, 1);
-                break;
+                /* The notification is sent with interrupts enabled. */
+                if (likely(per_cpu(tracer, cpu))) {
+                        ds_release_bts(per_cpu(tracer, cpu));
+                        per_cpu(tracer, cpu) = NULL;
+                }
         }
 
- out:
-        spin_unlock(&bts_tracer_lock);
         return NOTIFY_DONE;
 }
 
@@ -126,20 +134,6 @@ 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;
-
-        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");
@@ -147,10 +141,10 @@ static void bts_trace_print_header(struct seq_file *m)
 
 static enum print_line_t bts_trace_print_line(struct trace_iterator *iter)
 {
+        unsigned long symflags = TRACE_ITER_SYM_OFFSET;
         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);
 
@@ -226,11 +220,11 @@ static void trace_bts_at(const struct bts_trace *trace, void *at)
 /*
  * Collect the trace on the current cpu and write it into the ftrace buffer.
  *
- * pre: bts_tracer_lock must be locked
+ * pre: tracing must be suspended on the current cpu
  */
 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;
 
@@ -243,10 +237,9 @@ static void trace_bts_cpu(void *arg)
         if (unlikely(!this_tracer))
                 return;
 
-        ds_suspend_bts(this_tracer);
         trace = ds_read_bts(this_tracer);
         if (!trace)
-                goto out;
+                return;
 
         for (at = trace->ds.top; (void *)at < trace->ds.end;
              at += trace->ds.size)
@@ -255,18 +248,27 @@ static void trace_bts_cpu(void *arg)
         for (at = trace->ds.begin; (void *)at < trace->ds.top;
              at += trace->ds.size)
                 trace_bts_at(trace, at);
-
-out:
-        ds_resume_bts(this_tracer);
 }
 
 static void trace_bts_prepare(struct trace_iterator *iter)
 {
-        spin_lock(&bts_tracer_lock);
+        int cpu;
 
+        get_online_cpus();
+        for_each_online_cpu(cpu)
+                if (likely(per_cpu(tracer, cpu)))
+                        ds_suspend_bts(per_cpu(tracer, cpu));
+        /*
+         * We need to collect the trace on the respective cpu since ftrace
+         * implicitly adds the record for the current cpu.
+         * Once that is more flexible, we could collect the data from any cpu.
+         */
         on_each_cpu(trace_bts_cpu, iter->tr, 1);
 
-        spin_unlock(&bts_tracer_lock);
+        for_each_online_cpu(cpu)
+                if (likely(per_cpu(tracer, cpu)))
+                        ds_resume_bts(per_cpu(tracer, cpu));
+        put_online_cpus();
 }
 
 static void trace_bts_close(struct trace_iterator *iter)
@@ -276,11 +278,11 @@ static void trace_bts_close(struct trace_iterator *iter)
 
 void trace_hw_branch_oops(void)
 {
-        spin_lock(&bts_tracer_lock);
-
-        trace_bts_cpu(hw_branch_trace);
-
-        spin_unlock(&bts_tracer_lock);
+        if (this_tracer) {
+                ds_suspend_bts_noirq(this_tracer);
+                trace_bts_cpu(hw_branch_trace);
+                ds_resume_bts_noirq(this_tracer);
+        }
 }
 
 struct tracer bts_tracer __read_mostly =
@@ -293,7 +295,10 @@ struct tracer bts_tracer __read_mostly =
         .start          = bts_trace_start,
         .stop           = bts_trace_stop,
         .open           = trace_bts_prepare,
-        .close          = trace_bts_close
+        .close          = trace_bts_close,
+#ifdef CONFIG_FTRACE_SELFTEST
+        .selftest       = trace_selftest_startup_hw_branches,
+#endif /* CONFIG_FTRACE_SELFTEST */
 };
 
 __init static int init_bts_trace(void)