Disk cache: Add support for multithread tracing.

The current disk cache tracing is single threaded but the
new version of the cache is not (as in interesting stuff
happens on more than one thread)

BUG=241277
TEST=none

Review URL: https://chromiumcodereview.appspot.com/15197004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@202282 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 24 insertions, 11 deletions

diff --git a/net/disk_cache/trace.cc b/net/disk_cache/trace.cc
index ae0aa1a..56ebe9b 100644
--- a/net/disk_cache/trace.cc
+++ b/net/disk_cache/trace.cc
@@ -9,7 +9,9 @@
 #include <windows.h>
 #endif
 
+#include "base/lazy_instance.h"
 #include "base/logging.h"
+#include "base/synchronization/lock.h"
 #include "net/disk_cache/stress_support.h"
 
 // Change this value to 1 to enable tracing on a release build. By default,
@@ -31,6 +33,7 @@ const int kNumberOfEntries = 5000;  // 240 KB on 32bit, 480 KB on 64bit
 #endif
 
 bool s_trace_enabled = false;
+base::LazyInstance<base::Lock>::Leaky s_lock = LAZY_INSTANCE_INITIALIZER;
 
 struct TraceBuffer {
   int num_traces;
@@ -59,6 +62,8 @@ static TraceObject* s_trace_object = NULL;
 
 // Static.
 TraceObject* TraceObject::GetTraceObject() {
+  base::AutoLock lock(s_lock.Get());
+
   if (s_trace_object)
     return s_trace_object;
 
@@ -75,6 +80,7 @@ TraceObject::~TraceObject() {
 }
 
 void TraceObject::EnableTracing(bool enable) {
+  base::AutoLock lock(s_lock.Get());
   s_trace_enabled = enable;
 }
 
@@ -92,6 +98,8 @@ void InitTrace(void) {
 }
 
 void DestroyTrace(void) {
+  base::AutoLock lock(s_lock.Get());
+
   delete s_trace_buffer;
   s_trace_buffer = NULL;
   s_trace_object = NULL;
@@ -103,28 +111,33 @@ void Trace(const char* format, ...) {
 
   va_list ap;
   va_start(ap, format);
+  char line[kEntrySize + 2];
 
 #if defined(OS_WIN)
-  vsprintf_s(s_trace_buffer->buffer[s_trace_buffer->current], format, ap);
+  vsprintf_s(line, format, ap);
 #else
-  vsnprintf(s_trace_buffer->buffer[s_trace_buffer->current],
-            sizeof(s_trace_buffer->buffer[s_trace_buffer->current]), format,
-            ap);
+  vsnprintf(line, kEntrySize, format, ap);
 #endif
 
 #if defined(DISK_CACHE_TRACE_TO_LOG)
-  char line[kEntrySize + 2];
-  memcpy(line, s_trace_buffer->buffer[s_trace_buffer->current], kEntrySize);
   line[kEntrySize] = '\0';
   LOG(INFO) << line;
 #endif
 
-  s_trace_buffer->num_traces++;
-  s_trace_buffer->current++;
-  if (s_trace_buffer->current == kNumberOfEntries)
-    s_trace_buffer->current = 0;
-
   va_end(ap);
+
+  {
+    base::AutoLock lock(s_lock.Get());
+    if (!s_trace_buffer || !s_trace_enabled)
+      return;
+
+    memcpy(s_trace_buffer->buffer[s_trace_buffer->current], line, kEntrySize);
+
+    s_trace_buffer->num_traces++;
+    s_trace_buffer->current++;
+    if (s_trace_buffer->current == kNumberOfEntries)
+      s_trace_buffer->current = 0;
+  }
 }
 
 // Writes the last num_traces to the debugger output.