[tracing] Use trace thread for gpu process to initialize tracing

For non-zygote child gpu thread, start the trace thread in
ContentMainRunnerImpl() directly.

For zygote child gpu thread, start the trace thread in RunZygote after
zygote fork and featurelist init.

For Linux & ChromeOS, stop and restart the trace thread when entering
sandbox. Restarting trace thread has a caveat that delayed tasks would
will be lost unless we save them.

This is [3/?] CL of enabling tracing prior to sandboxing.

Bug: 380411640
Change-Id: I89fa94f63a709de0e3da4f8759098c9fff813bee
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6180639
Reviewed-by: Kinuko Yasuda <kinuko@chromium.org>
Reviewed-by: Etienne Pierre-Doray <etiennep@chromium.org>
Commit-Queue: Kramer Ge <fangzhoug@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1428704}

content/app/content_main_runner_impl.cc

@@ -658,7 +658,18 @@ NO_STACK_PROTECTOR int RunZygote(ContentMainDelegate* delegate) {
 
   MainFunctionParams main_params(command_line);
   main_params.zygote_child = true;
-  main_params.needs_startup_tracing_after_mojo_init = true;
+
+  if (process_type == switches::kGpuProcess) {
+    // Once Zygote forks and feature list initializes we can start a thread to
+    // begin tracing immediately.
+    // TODO(https://crbug.com/380411640): Enable for more processes other than
+    // GPU process.
+    tracing::EnableStartupTracingIfNeeded(/*with_thread=*/true);
+    tracing::InitTracingPostFeatureList(/*enable_consumer=*/false);
+    main_params.needs_startup_tracing_after_mojo_init = false;
+  } else {
+    main_params.needs_startup_tracing_after_mojo_init = true;
+  }
 
   // The hang watcher needs to be created once the feature list is available
   // but before the IO thread is started.
@@ -888,15 +899,27 @@ int ContentMainRunnerImpl::Initialize(ContentMainParams params) {
 #if BUILDFLAG(IS_POSIX) && !BUILDFLAG(IS_ANDROID) && !BUILDFLAG(IS_MAC)
   // A sandboxed process won't be able to allocate the SMB needed for startup
   // tracing until Mojo IPC support is brought up, at which point the Mojo
-  // broker will transparently broker the SMB creation.
+  // broker will transparently broker the SMB creation. Unless the sandboxed
-  if (!sandbox::policy::IsUnsandboxedSandboxType(
+  // process stops the trace threads when entering sandbox.
+  // TODO(https://crbug.com/380411640): Implement for other processes other than
+  // GPU process.
+  if (process_type != switches::kGpuProcess &&
+      !sandbox::policy::IsUnsandboxedSandboxType(
           sandbox::policy::SandboxTypeFromCommandLine(command_line))) {
     enable_startup_tracing = false;
     needs_startup_tracing_after_mojo_init_ = true;
   }
 #endif  // BUILDFLAG(IS_POSIX) && !BUILDFLAG(IS_ANDROID) && !BUILDFLAG(IS_MAC)
   if (enable_startup_tracing) {
-    tracing::EnableStartupTracingIfNeeded();
+    if (process_type == switches::kGpuProcess) {
+      // Without Zygote and posix sandbox we can start a thread to begin tracing
+      // immediately.
+      // TODO(https://crbug.com/380411640): Enable for more processes other than
+      // GPU process.
+      tracing::EnableStartupTracingIfNeeded(/*with_thread=*/true);
+    } else {
+      tracing::EnableStartupTracingIfNeeded(/*with_thread=*/false);
+    }
   }
   TRACE_EVENT0("startup,benchmark,rail", "ContentMainRunnerImpl::Initialize");
 
@@ -1112,6 +1135,9 @@ NO_STACK_PROTECTOR int ContentMainRunnerImpl::Run() {
               ContentMainDelegate::InvokedInChildProcess())) {
         InitializeFieldTrialAndFeatureList();
       }
+      if (process_type == switches::kGpuProcess) {
+        tracing::InitTracingPostFeatureList(/*enable_consumer=*/false);
+      }
       if (delegate_->ShouldInitializeMojo(
               ContentMainDelegate::InvokedInChildProcess())) {
         InitializeMojoCore();

content/gpu/gpu_main.cc

@@ -28,6 +28,7 @@
 #include "base/task/single_thread_task_executor.h"
 #include "base/task/thread_pool/thread_pool_instance.h"
 #include "base/threading/platform_thread.h"
+#include "base/threading/thread.h"
 #include "base/time/time.h"
 #include "base/timer/hi_res_timer_manager.h"
 #include "base/trace_event/trace_event.h"
@@ -44,6 +45,7 @@
 #include "content/public/common/content_switches.h"
 #include "content/public/common/main_function_params.h"
 #include "content/public/common/result_codes.h"
+#include "content/public/common/zygote/zygote_buildflags.h"
 #include "content/public/gpu/content_gpu_client.h"
 #include "gpu/command_buffer/service/gpu_switches.h"
 #include "gpu/config/gpu_driver_bug_list.h"
@@ -59,6 +61,7 @@
 #include "media/gpu/buildflags.h"
 #include "mojo/public/cpp/bindings/interface_endpoint_client.h"
 #include "mojo/public/cpp/bindings/sync_call_restrictions.h"
+#include "services/tracing/public/cpp/perfetto/perfetto_traced_process.h"
 #include "services/tracing/public/cpp/trace_startup.h"
 #include "services/tracing/public/cpp/trace_startup_config.h"
 #include "third_party/angle/src/gpu_info_util/SystemInfo.h"
@@ -206,11 +209,8 @@ void LoadMetalShaderCacheIfNecessary() {
 
 // Main function for starting the Gpu process.
 int GpuMain(MainFunctionParams parameters) {
-  if (tracing::TraceStartupConfig::GetInstance().IsEnabled()) {
+  TRACE_EVENT("gpu,startup", "GpuMain");
-    gl::StartupTrace::Startup();
-  }
 
-  TRACE_EVENT0("gpu", "GpuMain");
   base::CurrentProcess::GetInstance().SetProcessType(
       base::CurrentProcessType::PROCESS_GPU);
 
@@ -324,7 +324,6 @@ int GpuMain(MainFunctionParams parameters) {
             base::MessagePumpType::DEFAULT);
 #endif
   }
-  gl::StartupTrace::GetInstance()->BindToCurrentThread();
 
   base::PlatformThread::SetName("CrGpuMain");
   mojo::InterfaceEndpointClient::SetThreadNameSuffixForMetrics("GpuMain");
@@ -450,7 +449,6 @@ int GpuMain(MainFunctionParams parameters) {
   }
 
   DCHECK(tracing::IsTracingInitialized());
-  gl::StartupTrace::StarupDone();
 
   {
     TRACE_EVENT0("gpu", "Run Message Loop");
@@ -474,6 +472,14 @@ bool StartSandboxLinux(gpu::GpuWatchdogThread* watchdog_thread,
     sandbox::policy::SandboxLinux::GetInstance()->StopThread(watchdog_thread);
   }
 
+  base::Thread* trace_thread =
+      tracing::IsTracingInitialized()
+          ? tracing::PerfettoTracedProcess::GetTraceThread()
+          : nullptr;
+  if (trace_thread) {
+    sandbox::policy::SandboxLinux::GetInstance()->StopThread(trace_thread);
+  }
+
   // SandboxLinux::InitializeSandbox() must always be called
   // with only one thread.
   sandbox::policy::SandboxLinux::Options sandbox_options;
@@ -523,6 +529,10 @@ bool StartSandboxLinux(gpu::GpuWatchdogThread* watchdog_thread,
     watchdog_thread->Start();
   }
 
+  if (trace_thread) {
+    tracing::PerfettoTracedProcess::RestartThreadInSandbox();
+  }
+
   return res;
 }
 #endif  // BUILDFLAG(IS_LINUX) || BUILDFLAG(IS_CHROMEOS)

services/tracing/public/cpp/trace_startup.cc

@@ -47,17 +47,15 @@ using base::trace_event::TraceLog;
 }  // namespace
 
 bool g_tracing_initialized_after_featurelist = false;
+bool g_tracing_with_thread = false;
 
 bool IsTracingInitialized() {
   return g_tracing_initialized_after_featurelist;
 }
 
-void EnableStartupTracingIfNeeded() {
+void EnableStartupTracingIfNeeded(bool with_thread) {
   RegisterTracedValueProtoWriter();
 
-  // Create the PerfettoTracedProcess.
-  PerfettoTracedProcess::MaybeCreateInstance();
-
   // Initialize the client library's TrackRegistry to support trace points
   // during startup tracing. We don't setup the client library completely here
   // yet, because we don't have field trials loaded yet (which influence which
@@ -66,6 +64,14 @@ void EnableStartupTracingIfNeeded() {
   // setting up the client library?
   perfetto::internal::TrackRegistry::InitializeInstance();
 
+  // Create the PerfettoTracedProcess.
+  if (with_thread) {
+    g_tracing_with_thread = true;
+    PerfettoTracedProcess::MaybeCreateInstanceWithThread();
+  } else {
+    PerfettoTracedProcess::MaybeCreateInstance();
+  }
+
   // Ensure TraceLog is initialized first.
   // https://crbug.com/764357
   TraceLog::GetInstance();
@@ -106,7 +112,9 @@ void InitTracingPostFeatureList(bool enable_consumer) {
   DCHECK(base::FeatureList::GetInstance());
 
   // Create the PerfettoTracedProcess.
-  PerfettoTracedProcess::MaybeCreateInstance();
+  if (!g_tracing_with_thread) {
+    PerfettoTracedProcess::MaybeCreateInstance();
+  }
   PerfettoTracedProcess::Get().OnThreadPoolAvailable(enable_consumer);
 #if BUILDFLAG(IS_WIN)
   tracing::EnableETWExport();

services/tracing/public/cpp/trace_startup.h

@@ -35,7 +35,8 @@ bool COMPONENT_EXPORT(TRACING_CPP) IsTracingInitialized();
 // TODO(eseckler): Consider allocating the SMB in parent processes outside the
 // sandbox and supply it via the command line. Then, we can revert to call this
 // earlier and from fewer places again.
-void COMPONENT_EXPORT(TRACING_CPP) EnableStartupTracingIfNeeded();
+void COMPONENT_EXPORT(TRACING_CPP)
+    EnableStartupTracingIfNeeded(bool with_thread = false);
 
 // Enable startup tracing for the current process with the provided config. Sets
 // up ProducerClient and trace event and/or sampler profiler data sources, and

ui/gl/startup_trace.h

@@ -77,20 +77,6 @@ class GL_EXPORT StartupTrace {
 
 }  // namespace gl
 
-// Generate a unique variable name with a given prefix.
+#define GPU_STARTUP_TRACE_EVENT(name) TRACE_EVENT("gpu,startup", name);
-#define GPU_STARTUP_TRACE_INTERNAL_CONCAT2(a, b) a##b
-#define GPU_STARTUP_TRACE_INTERNAL_CONCAT(a, b) \
-  GPU_STARTUP_TRACE_INTERNAL_CONCAT2(a, b)
-#define GPU_STARTUP_TRACE_UID(prefix) \
-  GPU_STARTUP_TRACE_INTERNAL_CONCAT(prefix, __LINE__)
-
-#define GPU_STARTUP_TRACE_EVENT(name)                                       \
-  gl::StartupTrace::ScopedStage GPU_STARTUP_TRACE_UID(scoped_gpu_trace){0}; \
-  if (gl::StartupTrace::IsEnabled()) {                                      \
-    GPU_STARTUP_TRACE_UID(scoped_gpu_trace) =                               \
-        gl::StartupTrace::GetInstance()->AddStage(name);                    \
-  } else {                                                                  \
-    TRACE_EVENT0("gpu,startup", name);                                      \
-  }
 
 #endif  // UI_GL_STARTUP_TRACE_H_