global_state.cpp

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Hash : 36c3e0f5
Author :
Date : 2023-01-17T17:42:59

Implement "Shared Context Mutex" functionality.

Existing implementation uses single `GlobalMutex` for
- EGL calls
- GL calls for Contexts with concurrent access.

This CL introduces abstract `egl::ContextMutex` with two
implementations:
- SingleContextMutex;
- SharedContextMutex<Mutex>;

Note:
`std::mutex` is used in this commit. It is very easy to change mutex
type either at compile-time or at run-time (single type per Display).

When Context:
- is not Shared;
- does not use `EGLImage`s;
- does not use EGL_DISPLAY_TEXTURE_SHARE_GROUP_ANGLE
- does not use EGL_DISPLAY_SEMAPHORE_SHARE_GROUP_ANGLE
then it will be using `SingleContextMutex` with minimal overhead.

Before such Context is used as `shareContext` or uses `EGLImage`
its mutex replaced by `SharedContextMutex<Mutex>`.

The `GlobalMutex` is only used for EGL calls, while `egl::ContextMutex`
implementations for GL calls. Because some EGL calls use Context,
explicit `egl::ContextMutex` lock is required. This is implemented by
generating "egl_context_mutex_autogen.h" header, and insertion of
`ANGLE_EGL_SCOPED_CONTEXT_LOCK()` macro before `ANGLE_EGL_VALIDATE()`
in each EGL entry point. Implementation in "egl_context_lock_impl.h"
returns lock for required APIs. Special cases of `egl::ContextMutex`
lock handled separately. `std::unique_lock<>` is not used for
performance reasons.

`egl::ContextMutex` explicitly locked when capturing EGL calls.

Fixes EGLImage problem:
https://chromium.googlesource.com/angle/angle/+/e18240d136d15e5cdfa4fa4a6355ca21c8d807b6
Mark contexts as shared when importing EGL images.

Details:
- EGLImage inherits Context's mutex when created.
Mutex is used when the EGLImage accessed or destroyed.
- When EGLImage is used in Context with other `egl::ContextMutex`,
two mutexes are merged into one.
- After the mutex merge, Context Groups will remain separate,
but will not be able to run in parallel.

Fixes race when checking `context->isShared()` in the
`SCOPED_SHARE_CONTEXT_LOCK()` macro. One Context may start executing GL
call while not "Shared", but become "Shared" inside the call. New
(second) "Shared" Context may immediately start using GL and potentially
corrupt some "Shared" state.

Possible performance benefit: allows parallel execution in some cases,
when single `GlobalMutex` would block.

Important note:
Process of replacing the `SingleContextMutex` by
`SharedContextMutex<Mutex>` is not 100% safe. This mean that
original Context may still be using `SingleContextMutex` after
activating `SharedContextMutex<Mutex>`. However, this was always
the case before introduction of this CL. Old `Context::mShared`
member update was not synchronized in any way at all. In other
words, this solution does not 100% fix the original problem.
For 100% safe solution `SingleContextMutex` should not be used
(always pass `SharedContextMutex<Mutex>` to the `gl::Context`
constructor). See `lockAndActivateSharedContextMutex()` for more
details.

CL adds new build option:
angle_enable_shared_context_mutex = true

Behavior with other build options:
- When:
`angle_enable_shared_context_mutex` is disabled or
`angle_enable_share_context_lock` is disabled or
`angle_force_context_check_every_call` is enabled,
Contexts will always have `SingleContextMutex`, however it will be
only used in special cases. `SCOPED_SHARE_CONTEXT_LOCK()` will use
`GlobalMutex` when applicable.
- Otherwise, `SCOPED_SHARE_CONTEXT_LOCK()` will use `egl::ContextMutex`.

Some GFXBench "1080p Driver Overhead 2 Offscreen" performance numbers.
Tested on S906B (Samsung Galaxy S22+) on old ANGLE base:
https://chromium.googlesource.com/angle/angle/+/807c94ea85e046c6f279d081d99f0fb1bcf1191a
Capture/Replay: Adjust tests do adhere to capture limits

Each test result is an average frame number from 6 runs.

SingleContextMutex 6579 ( +0.13%)
(old) GetContextLock() (mShared is false) 6570

Forced `mShared = true` or NOT using `SingleContextMutex`.

SharedContextMutex<std::mutex> FORCE 5061 (-22.97%)
(old) GetContextLock() FORCE 4766 (-27.46%)

Bug: angleproject:6957
Bug: chromium:1336126
Change-Id: Idcd919f9d4bf482b9ae489bd8b4415ec96048e32
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/4374545
Reviewed-by: Geoff Lang <geofflang@chromium.org>
Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org>
Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org>

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src/libGLESv2/global_state.cpp

//
// Copyright 2014 The ANGLE Project Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
//

// global_state.cpp : Implements functions for querying the thread-local GL and EGL state.

#include "libGLESv2/global_state.h"

#include "common/debug.h"
#include "common/platform.h"
#include "common/system_utils.h"
#include "libANGLE/ErrorStrings.h"
#include "libANGLE/Thread.h"
#include "libGLESv2/resource.h"

#include <atomic>
#if defined(ANGLE_PLATFORM_APPLE)
#    include <dispatch/dispatch.h>
#endif
namespace egl
{
namespace
{
ANGLE_REQUIRE_CONSTANT_INIT gl::Context *g_LastContext(nullptr);
static_assert(std::is_trivially_destructible<decltype(g_LastContext)>::value,
              "global last context is not trivially destructible");

// Called only on Android platform
[[maybe_unused]] void ThreadCleanupCallback(void *ptr)
{
    ANGLE_SCOPED_GLOBAL_LOCK();
    angle::PthreadKeyDestructorCallback(ptr);
}

Thread *AllocateCurrentThread()
{
    Thread *thread;
    {
        // Global thread intentionally leaked.
        // Display TLS data is also intentionally leaked.
        ANGLE_SCOPED_DISABLE_LSAN();
        thread = new Thread();
#if defined(ANGLE_PLATFORM_APPLE)
        SetCurrentThreadTLS(thread);
#else
        gCurrentThread = thread;
#endif

        Display::InitTLS();
    }

    // Initialize current-context TLS slot
    gl::SetCurrentValidContext(nullptr);

#if defined(ANGLE_PLATFORM_ANDROID)
    static pthread_once_t keyOnce                 = PTHREAD_ONCE_INIT;
    static angle::TLSIndex gThreadCleanupTLSIndex = TLS_INVALID_INDEX;

    // Create thread cleanup TLS slot
    auto CreateThreadCleanupTLSIndex = []() {
        gThreadCleanupTLSIndex = angle::CreateTLSIndex(ThreadCleanupCallback);
    };
    pthread_once(&keyOnce, CreateThreadCleanupTLSIndex);
    ASSERT(gThreadCleanupTLSIndex != TLS_INVALID_INDEX);

    // Initialize thread cleanup TLS slot
    angle::SetTLSValue(gThreadCleanupTLSIndex, thread);
#endif  // ANGLE_PLATFORM_ANDROID

    ASSERT(thread);
    return thread;
}

}  // anonymous namespace

#if defined(ANGLE_PLATFORM_APPLE)
// TODO(angleproject:6479): Due to a bug in Apple's dyld loader, `thread_local` will cause
// excessive memory use. Temporarily avoid it by using pthread's thread
// local storage instead.
// https://bugs.webkit.org/show_bug.cgi?id=228240

static angle::TLSIndex GetCurrentThreadTLSIndex()
{
    static angle::TLSIndex CurrentThreadIndex = TLS_INVALID_INDEX;
    static dispatch_once_t once;
    dispatch_once(&once, ^{
      ASSERT(CurrentThreadIndex == TLS_INVALID_INDEX);
      CurrentThreadIndex = angle::CreateTLSIndex(nullptr);
    });
    return CurrentThreadIndex;
}
Thread *GetCurrentThreadTLS()
{
    angle::TLSIndex CurrentThreadIndex = GetCurrentThreadTLSIndex();
    ASSERT(CurrentThreadIndex != TLS_INVALID_INDEX);
    return static_cast<Thread *>(angle::GetTLSValue(CurrentThreadIndex));
}
void SetCurrentThreadTLS(Thread *thread)
{
    angle::TLSIndex CurrentThreadIndex = GetCurrentThreadTLSIndex();
    ASSERT(CurrentThreadIndex != TLS_INVALID_INDEX);
    angle::SetTLSValue(CurrentThreadIndex, thread);
}
#else
thread_local Thread *gCurrentThread = nullptr;
#endif

gl::Context *GetGlobalLastContext()
{
    return g_LastContext;
}

void SetGlobalLastContext(gl::Context *context)
{
    g_LastContext = context;
}

// This function causes an MSAN false positive, which is muted. See https://crbug.com/1211047
// It also causes a flaky false positive in TSAN. http://crbug.com/1223970
ANGLE_NO_SANITIZE_MEMORY ANGLE_NO_SANITIZE_THREAD Thread *GetCurrentThread()
{
#if defined(ANGLE_PLATFORM_APPLE)
    Thread *current = GetCurrentThreadTLS();
#else
    Thread *current       = gCurrentThread;
#endif
    return (current ? current : AllocateCurrentThread());
}

void SetContextCurrent(Thread *thread, gl::Context *context)
{
#if defined(ANGLE_PLATFORM_APPLE)
    Thread *currentThread = GetCurrentThreadTLS();
#else
    Thread *currentThread = gCurrentThread;
#endif
    ASSERT(currentThread);
    currentThread->setCurrent(context);

    gl::SetCurrentValidContext(context);

#if defined(ANGLE_FORCE_CONTEXT_CHECK_EVERY_CALL)
    DirtyContextIfNeeded(context);
#endif
}

ScopedSyncCurrentContextFromThread::ScopedSyncCurrentContextFromThread(egl::Thread *thread)
    : mThread(thread)
{
    ASSERT(mThread);
}

ScopedSyncCurrentContextFromThread::~ScopedSyncCurrentContextFromThread()
{
    SetContextCurrent(mThread, mThread->getContext());
}

}  // namespace egl

namespace gl
{
void GenerateContextLostErrorOnContext(Context *context)
{
    if (context && context->isContextLost())
    {
        context->validationError(angle::EntryPoint::Invalid, GL_CONTEXT_LOST, err::kContextLost);
    }
}

void GenerateContextLostErrorOnCurrentGlobalContext()
{
    // If the client starts issuing GL calls before ANGLE has had a chance to initialize,
    // GenerateContextLostErrorOnCurrentGlobalContext can be called before AllocateCurrentThread has
    // had a chance to run. Calling GetCurrentThread() ensures that TLS thread state is set up.
    egl::GetCurrentThread();

    GenerateContextLostErrorOnContext(GetGlobalContext());
}
}  // namespace gl

#if defined(ANGLE_PLATFORM_WINDOWS) && !defined(ANGLE_STATIC)
namespace egl
{

namespace
{

void DeallocateCurrentThread()
{
    SafeDelete(gCurrentThread);
}

bool InitializeProcess()
{
    EnsureDebugAllocated();
    AllocateGlobalMutex();
    return AllocateCurrentThread() != nullptr;
}

void TerminateProcess()
{
    DeallocateDebug();
    DeallocateGlobalMutex();
    DeallocateCurrentThread();
}

}  // anonymous namespace

}  // namespace egl

namespace
{
// The following WaitForDebugger code is based on SwiftShader. See:
// https://cs.chromium.org/chromium/src/third_party/swiftshader/src/Vulkan/main.cpp
#    if defined(ANGLE_ENABLE_ASSERTS) && !defined(ANGLE_ENABLE_WINDOWS_UWP)
INT_PTR CALLBACK DebuggerWaitDialogProc(HWND hwnd, UINT uMsg, WPARAM wParam, LPARAM lParam)
{
    RECT rect;

    switch (uMsg)
    {
        case WM_INITDIALOG:
            ::GetWindowRect(GetDesktopWindow(), &rect);
            ::SetWindowPos(hwnd, HWND_TOP, rect.right / 2, rect.bottom / 2, 0, 0, SWP_NOSIZE);
            ::SetTimer(hwnd, 1, 100, NULL);
            return TRUE;
        case WM_COMMAND:
            if (LOWORD(wParam) == IDCANCEL)
            {
                ::EndDialog(hwnd, 0);
            }
            break;
        case WM_TIMER:
            if (angle::IsDebuggerAttached())
            {
                ::EndDialog(hwnd, 0);
            }
    }

    return FALSE;
}

void WaitForDebugger(HINSTANCE instance)
{
    if (angle::IsDebuggerAttached())
        return;

    HRSRC dialog = ::FindResourceA(instance, MAKEINTRESOURCEA(IDD_DIALOG1), MAKEINTRESOURCEA(5));
    if (!dialog)
    {
        printf("Error finding wait for debugger dialog. Error %lu.\n", ::GetLastError());
        return;
    }

    DLGTEMPLATE *dialogTemplate = reinterpret_cast<DLGTEMPLATE *>(::LoadResource(instance, dialog));
    ::DialogBoxIndirectA(instance, dialogTemplate, NULL, DebuggerWaitDialogProc);
}
#    else
void WaitForDebugger(HINSTANCE instance) {}
#    endif  // defined(ANGLE_ENABLE_ASSERTS) && !defined(ANGLE_ENABLE_WINDOWS_UWP)
}  // namespace

extern "C" BOOL WINAPI DllMain(HINSTANCE instance, DWORD reason, LPVOID)
{
    switch (reason)
    {
        case DLL_PROCESS_ATTACH:
            if (angle::GetEnvironmentVar("ANGLE_WAIT_FOR_DEBUGGER") == "1")
            {
                WaitForDebugger(instance);
            }
            return static_cast<BOOL>(egl::InitializeProcess());

        case DLL_THREAD_ATTACH:
            return static_cast<BOOL>(egl::AllocateCurrentThread() != nullptr);

        case DLL_THREAD_DETACH:
            egl::DeallocateCurrentThread();
            break;

        case DLL_PROCESS_DETACH:
            egl::TerminateProcess();
            break;
    }

    return TRUE;
}
#endif  // defined(ANGLE_PLATFORM_WINDOWS) && !defined(ANGLE_STATIC)

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