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// Copyright 2025 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "base/android/background_thread_pool_field_trial.h"
#include <optional>
#include <string>
#include <string_view>
#include <utility>
#include "base/base_switches.h"
#include "base/check_op.h"
#include "base/command_line.h"
#include "base/compiler_specific.h"
#include "base/features.h"
#include "base/logging.h"
#include "base/strings/strcat.h"
#include "base/strings/string_number_conversions.h"
#include "base/synchronization/lock_impl.h"
namespace base {
namespace features {
BASE_FEATURE(kBackgroundThreadPoolFieldTrial,
"BackgroundThreadPoolFieldTrial",
FEATURE_DISABLED_BY_DEFAULT);
// |kBackgroundThreadPoolFieldTrialConfig| is queried only by the Java layer
// using CachedFlags, so mark we mark it as unused to make the C++ compiler
// happy.
#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wunused-variable"
BASE_FEATURE_PARAM(int,
kBackgroundThreadPoolFieldTrialConfig,
&kBackgroundThreadPoolFieldTrial,
"config",
0);
#pragma clang diagnostic pop
} // namespace features
namespace android {
// The global cached configuration of the trial.
std::optional<BackgroundThreadPoolFieldTrial::Configuration>
BackgroundThreadPoolFieldTrial::s_configuration_;
void BackgroundThreadPoolFieldTrial::Initialize() {
s_configuration_ = ReadConfigurationFromCommandLine();
}
BackgroundThreadPoolFieldTrial::Configuration
BackgroundThreadPoolFieldTrial::ReadConfigurationFromCommandLine() {
DCHECK(base::CommandLine::InitializedForCurrentProcess());
std::string value_str = CommandLine::ForCurrentProcess()->GetSwitchValueASCII(
switches::kBackgroundThreadPoolFieldTrial);
if (value_str.empty()) {
return Configuration::kDisabled;
}
int value = -1;
if (!base::StringToInt(value_str, &value) ||
value < static_cast<int>(Configuration::kDisabled) ||
value > static_cast<int>(Configuration::kConfigurationMax)) {
return Configuration::kDisabled;
}
return Configuration(value);
}
ALWAYS_INLINE BackgroundThreadPoolFieldTrial::Configuration
BackgroundThreadPoolFieldTrial::GetConfiguration() {
// For the few lock instances where the configuration is read very early, we
// return |kDisabled|.
return s_configuration_.has_value() ? Configuration(*s_configuration_)
: Configuration::kDisabled;
}
#if BUILDFLAG(ENABLE_MUTEX_PRIORITY_INHERITANCE)
BackgroundThreadPoolFieldTrial::TrialInfo
BackgroundThreadPoolFieldTrial::GetPISupportedTrialInfo() {
const std::string_view kVersionSuffix = "_20250505";
std::string_view group_name;
switch (GetConfiguration()) {
case Configuration::kPISupportedTrialControl:
group_name = "Control";
break;
case Configuration::kPISupportedTrialEnabledPILocksOnly:
group_name = "EnabledPILocksOnly";
break;
case Configuration::kPISupportedTrialEnabledBGThreadPoolOnly:
group_name = "EnabledBGThreadPoolOnly";
break;
case Configuration::kPISupportedTrialEnabledBoth:
group_name = "EnabledBoth";
break;
default:
LOG(FATAL) << "configuration value "
<< static_cast<int>(GetConfiguration())
<< " should not have called" << __PRETTY_FUNCTION__;
__builtin_unreachable();
}
return TrialInfo("AndroidBackgroundThreadPoolPISupportedSynthetic",
base::StrCat({group_name, kVersionSuffix}));
}
#endif // BUILDFLAG(ENABLE_MUTEX_PRIORITY_INHERITANCE)
BackgroundThreadPoolFieldTrial::TrialInfo
BackgroundThreadPoolFieldTrial::GetGeneralTrialInfo() {
const std::string_view kVersionSuffix = "_20250505";
std::string_view group_name;
switch (GetConfiguration()) {
case Configuration::kGeneralTrialControl:
group_name = "Control";
break;
case Configuration::kGeneralTrialEnabledBGThreadPool:
group_name = "Enabled";
break;
default:
LOG(FATAL) << "configuration value "
<< static_cast<int>(GetConfiguration())
<< " should not have called" << __PRETTY_FUNCTION__;
__builtin_unreachable();
}
return TrialInfo("AndroidBackgroundThreadPoolGeneralSynthetic",
base::StrCat({group_name, kVersionSuffix}));
}
bool BackgroundThreadPoolFieldTrial::ShouldUsePriorityInheritanceLocks() {
switch (GetConfiguration()) {
#if BUILDFLAG(ENABLE_MUTEX_PRIORITY_INHERITANCE)
case Configuration::kPISupportedTrialEnabledPILocksOnly:
case Configuration::kPISupportedTrialEnabledBoth:
return base::KernelSupportsPriorityInheritanceFutex();
#endif // BUILDFLAG(ENABLE_MUTEX_PRIORITY_INHERITANCE)
default:
return false;
}
}
bool BackgroundThreadPoolFieldTrial::ShouldUseBackgroundThreadPool() {
switch (GetConfiguration()) {
#if BUILDFLAG(ENABLE_MUTEX_PRIORITY_INHERITANCE)
case Configuration::kPISupportedTrialEnabledBGThreadPoolOnly:
case Configuration::kPISupportedTrialEnabledBoth:
return base::KernelSupportsPriorityInheritanceFutex();
#endif // BUILDFLAG(ENABLE_MUTEX_PRIORITY_INHERITANCE)
case Configuration::kGeneralTrialEnabledBGThreadPool:
return true;
default:
return false;
}
}
std::optional<BackgroundThreadPoolFieldTrial::TrialInfo>
BackgroundThreadPoolFieldTrial::GetTrialInfo() {
switch (GetConfiguration()) {
#if BUILDFLAG(ENABLE_MUTEX_PRIORITY_INHERITANCE)
case Configuration::kPISupportedTrialControl:
case Configuration::kPISupportedTrialEnabledPILocksOnly:
case Configuration::kPISupportedTrialEnabledBGThreadPoolOnly:
case Configuration::kPISupportedTrialEnabledBoth:
return base::KernelSupportsPriorityInheritanceFutex()
? std::make_optional(GetPISupportedTrialInfo())
: std::nullopt;
#endif // BUILDFLAG(ENABLE_MUTEX_PRIORITY_INHERITANCE)
case Configuration::kGeneralTrialControl:
case Configuration::kGeneralTrialEnabledBGThreadPool:
return GetGeneralTrialInfo();
default:
return std::nullopt;
}
}
#if BUILDFLAG(ENABLE_MUTEX_PRIORITY_INHERITANCE)
ScopedUsePriorityInheritanceLocksForTesting::
ScopedUsePriorityInheritanceLocksForTesting()
: reset_config_value_(&BackgroundThreadPoolFieldTrial::s_configuration_,
BackgroundThreadPoolFieldTrial::Configuration::
kPISupportedTrialEnabledPILocksOnly) {}
ScopedUsePriorityInheritanceLocksForTesting::
~ScopedUsePriorityInheritanceLocksForTesting() = default;
#endif // BUILDFLAG(ENABLE_MUTEX_PRIORITY_INHERITANCE)
} // namespace android
} // namespace base
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