111 lines
5 KiB
Diff
111 lines
5 KiB
Diff
Origin: upstream, https://github.com/mypaint/mypaint/commit/356716e7bacfcbb1f3ab80171fea405fdd10b2b9
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Bug-Debian: https://bugs.debian.org/1079663
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From 356716e7bacfcbb1f3ab80171fea405fdd10b2b9 Mon Sep 17 00:00:00 2001
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From: Red Rozenglass <rozenglass@protonmail.com>
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Date: Fri, 11 Sep 2020 02:43:49 +0300
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Subject: [PATCH] Acquire/release the GIL while processing tile requests
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Fixes crashes on some Linux distros, potentially improves performance.
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When handling tile requests we currently use an openmp critical block in a
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callback registered with libmypaint. The callback calls into Python code
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without locking the GIL. This sometimes crashes mypaint in numpy's memory
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cache allocator on some Linux distros that compile numpy with run-time
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asserts (without `-DNDEBUG`), like Gentoo, as numpy uses Python's GIL
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internally as a locking mechanism for its non-thread-safe global cache
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management.
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Acquiring the GIL in the C callback, before calling into Python, ensures
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that the GIL is still locked by the current thread when it reaches numpy's
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code, and thus prevents the crashes. We yield the GIL whenever Python code
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calls again into libmypaint, This allows other threads to acquire it, and
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concurrent callbacks to run, which prevents deadlocks that would otherwise
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happen while waiting for all the callbacks to finish on Python's side. When
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libmypaint is done we re-acquire the GIL, and return up to the callback
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where the GIL is released again after some Python reference count
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bookkeeping.
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The OpenMP critical block is no longer necessary after introducing the GIL
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locking mechanism. This would potentially improve performance as the C code
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in libmypaint can process multiple callbacks at the same time during the
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`Py_BEGIN_ALLOW_THREADS' period that yields the GIL.
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---
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lib/brush.hpp | 16 ++++++++++++++--
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lib/pythontiledsurface.cpp | 7 +++++--
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lib/tiledsurface.hpp | 4 +++-
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3 files changed, 22 insertions(+), 5 deletions(-)
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diff --git a/lib/brush.hpp b/lib/brush.hpp
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index f717a42df..0db455377 100644
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--- a/lib/brush.hpp
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+++ b/lib/brush.hpp
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@@ -66,13 +66,25 @@ class Brush {
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bool stroke_to (Surface * surface, float x, float y, float pressure, float xtilt, float ytilt, double dtime, float viewzoom, float viewrotation, float barrel_rotation)
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{
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MyPaintSurface2 *c_surface = surface->get_surface2_interface();
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- return mypaint_brush_stroke_to_2(c_brush, c_surface, x, y, pressure, xtilt, ytilt, dtime, viewzoom, viewrotation, barrel_rotation);
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+ bool stroke_finished_or_empty;
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+
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+ Py_BEGIN_ALLOW_THREADS
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+ stroke_finished_or_empty = mypaint_brush_stroke_to_2(c_brush, c_surface, x, y, pressure, xtilt, ytilt, dtime, viewzoom, viewrotation, barrel_rotation);
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+ Py_END_ALLOW_THREADS
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+
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+ return stroke_finished_or_empty;
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}
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bool stroke_to_linear (Surface * surface, float x, float y, float pressure, float xtilt, float ytilt, double dtime, float viewzoom, float viewrotation, float barrel_rotation)
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{
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MyPaintSurface2 *c_surface = surface->get_surface2_interface();
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- return mypaint_brush_stroke_to_2_linearsRGB(c_brush, c_surface, x, y, pressure, xtilt, ytilt, dtime, viewzoom, viewrotation, barrel_rotation);
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+ bool stroke_finished_or_empty;
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+
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+ Py_BEGIN_ALLOW_THREADS
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+ stroke_finished_or_empty = mypaint_brush_stroke_to_2_linearsRGB(c_brush, c_surface, x, y, pressure, xtilt, ytilt, dtime, viewzoom, viewrotation, barrel_rotation);
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+ Py_END_ALLOW_THREADS
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+
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+ return stroke_finished_or_empty;
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}
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double get_total_stroke_painting_time()
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diff --git a/lib/pythontiledsurface.cpp b/lib/pythontiledsurface.cpp
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index 46c515c99..2c6e773db 100644
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--- a/lib/pythontiledsurface.cpp
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+++ b/lib/pythontiledsurface.cpp
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@@ -36,8 +36,9 @@ tile_request_start(MyPaintTiledSurface2 *tiled_surface, MyPaintTileRequest *requ
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const int ty = request->ty;
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PyArrayObject* rgba = NULL;
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-#pragma omp critical
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{
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+ PyGILState_STATE gstate = PyGILState_Ensure();
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+
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rgba = (PyArrayObject*)PyObject_CallMethod(self->py_obj, "_get_tile_numpy", "(iii)", tx, ty, readonly);
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if (rgba == NULL) {
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request->buffer = NULL;
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@@ -59,7 +60,9 @@ tile_request_start(MyPaintTiledSurface2 *tiled_surface, MyPaintTileRequest *requ
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Py_DECREF((PyObject *)rgba);
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request->buffer = (uint16_t*)PyArray_DATA(rgba);
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}
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-} // #end pragma opt critical
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+
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+ PyGILState_Release(gstate);
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+}
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}
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diff --git a/lib/tiledsurface.hpp b/lib/tiledsurface.hpp
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index 3a6b2e61d..d1a5d1307 100644
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--- a/lib/tiledsurface.hpp
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+++ b/lib/tiledsurface.hpp
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@@ -66,7 +66,9 @@ class TiledSurface : public Surface {
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MyPaintRectangle* rects = this->bbox_rectangles;
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MyPaintRectangles bboxes = {BBOXES, rects};
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- mypaint_surface2_end_atomic((MyPaintSurface2 *)c_surface, &bboxes);
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+ Py_BEGIN_ALLOW_THREADS
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+ mypaint_surface2_end_atomic((MyPaintSurface2 *)c_surface, &bboxes);
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+ Py_END_ALLOW_THREADS
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// The capacity of the bounding box array will most often exceed the number
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// of rectangles that are actually used. The call to mypaint_surface_end_atomic
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