Jacques Lucke
c29c61f840
As described in the comment on `BLI_task_isolate`, deadlocks can happen when isolation is used with threading primitives that separate spawning tasks from executing them. All threads are waiting the tasks to complete but no thread is able to continue working due to task isolation. The fix is to not pass lazy-threading hints through task isolations. This way isolated regions can't create new tasks in a scheduler further up the call stack. This may lead to minor slowdowns because less threading may be used. It's generally possible to get rid of the slowdown again by sending the lazy-threading hint before entering the isolated region.
77 lines
2.0 KiB
C++
77 lines
2.0 KiB
C++
/* SPDX-License-Identifier: GPL-2.0-or-later */
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/** \file
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* \ingroup bli
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*
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* Task scheduler initialization.
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*/
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#include "MEM_guardedalloc.h"
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#include "BLI_lazy_threading.hh"
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#include "BLI_task.h"
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#include "BLI_threads.h"
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#ifdef WITH_TBB
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/* Need to include at least one header to get the version define. */
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# include <tbb/blocked_range.h>
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# include <tbb/task_arena.h>
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# if TBB_INTERFACE_VERSION_MAJOR >= 10
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# include <tbb/global_control.h>
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# define WITH_TBB_GLOBAL_CONTROL
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# endif
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#endif
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/* Task Scheduler */
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static int task_scheduler_num_threads = 1;
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#ifdef WITH_TBB_GLOBAL_CONTROL
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static tbb::global_control *task_scheduler_global_control = nullptr;
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#endif
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void BLI_task_scheduler_init()
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{
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#ifdef WITH_TBB_GLOBAL_CONTROL
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const int threads_override_num = BLI_system_num_threads_override_get();
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if (threads_override_num > 0) {
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/* Override number of threads. This settings is used within the lifetime
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* of tbb::global_control, so we allocate it on the heap. */
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task_scheduler_global_control = MEM_new<tbb::global_control>(
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__func__, tbb::global_control::max_allowed_parallelism, threads_override_num);
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task_scheduler_num_threads = threads_override_num;
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}
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else {
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/* Let TBB choose the number of threads. For (legacy) code that calls
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* BLI_task_scheduler_num_threads() we provide the system thread count.
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* Ideally such code should be rewritten not to use the number of threads
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* at all. */
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task_scheduler_num_threads = BLI_system_thread_count();
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}
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#else
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task_scheduler_num_threads = BLI_system_thread_count();
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#endif
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}
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void BLI_task_scheduler_exit()
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{
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#ifdef WITH_TBB_GLOBAL_CONTROL
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MEM_delete(task_scheduler_global_control);
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#endif
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}
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int BLI_task_scheduler_num_threads()
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{
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return task_scheduler_num_threads;
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}
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void BLI_task_isolate(void (*func)(void *userdata), void *userdata)
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{
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#ifdef WITH_TBB
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blender::lazy_threading::ReceiverIsolation isolation;
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tbb::this_task_arena::isolate([&] { func(userdata); });
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#else
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func(userdata);
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#endif
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}
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