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| author | Morten Johan Sørvig <morten.sorvig@qt.io> | 2020-03-31 00:53:41 +0200 |
|---|---|---|
| committer | Morten Johan Sørvig <morten.sorvig@qt.io> | 2020-04-05 22:20:55 +0200 |
| commit | f9137c8c6ec9174a9b92234bc8b49ee2445798b9 (patch) | |
| tree | 6df1a54d433bc633edfbd3638c3efdb36cb27cd8 /src/gui | |
| parent | 1c23d34ad4bdd67dec6d501d91087823dc9ea358 (diff) | |
Wasm: don’t deadlock on parallel image conversions
A special restriction of threads on WebAssembly is
that you should not block the main thread, also not
to wait for worker threads.
For example, blocking the main thread may prevent the
browser from starting a new web worker to service the
pthread the main thread is waiting for.
We may be able create an abstraction to support use
cases like this (most likely using emscripten asyncify),
but for disable use of threads to avoid deadlocking.
Change-Id: I35edd5e1bb465e2549fa7cc4288b47dcd2e4244b
Reviewed-by: Allan Sandfeld Jensen <allan.jensen@qt.io>
Diffstat (limited to 'src/gui')
| -rw-r--r-- | src/gui/image/qimage_conversions.cpp | 11 |
1 files changed, 8 insertions, 3 deletions
diff --git a/src/gui/image/qimage_conversions.cpp b/src/gui/image/qimage_conversions.cpp index 853bbe4f8e..34d2b8d8c7 100644 --- a/src/gui/image/qimage_conversions.cpp +++ b/src/gui/image/qimage_conversions.cpp @@ -48,6 +48,11 @@ #if QT_CONFIG(thread) #include <qsemaphore.h> #include <qthreadpool.h> +#ifdef Q_OS_WASM +// WebAssembly has threads; however we can't block the main thread. +#else +#define QT_USE_THREAD_PARALLEL_IMAGE_CONVERSIONS +#endif #endif QT_BEGIN_NAMESPACE @@ -227,7 +232,7 @@ void convert_generic(QImageData *dest, const QImageData *src, Qt::ImageConversio } }; -#if QT_CONFIG(thread) +#ifdef QT_USE_THREAD_PARALLEL_IMAGE_CONVERSIONS int segments = src->nbytes / (1<<16); segments = std::min(segments, src->height); @@ -281,7 +286,7 @@ void convert_generic_to_rgb64(QImageData *dest, const QImageData *src, Qt::Image destData += dest->bytes_per_line; } }; -#if QT_CONFIG(thread) +#ifdef QT_USE_THREAD_PARALLEL_IMAGE_CONVERSIONS int segments = src->nbytes / (1<<16); segments = std::min(segments, src->height); @@ -388,7 +393,7 @@ bool convert_generic_inplace(QImageData *data, QImage::Format dst_format, Qt::Im destData += params.bytesPerLine; } }; -#if QT_CONFIG(thread) +#ifdef QT_USE_THREAD_PARALLEL_IMAGE_CONVERSIONS int segments = data->nbytes / (1<<16); segments = std::min(segments, data->height); if (segments > 1) { |