add the io_uring scheduler as the default system scheduler on linux

.github/workflows/ci.gpu.yml

@@ -67,7 +67,7 @@ jobs:
           # Configure
           cmake -S . -B build -GNinja \
             -DSTDEXEC_ENABLE_CUDA=ON \
-            -DSTDEXEC_ENABLE_IO_URING_TESTS=OFF \
+            -DSTDEXEC_ENABLE_IO_URING=OFF \
             -DCMAKE_BUILD_TYPE=${{ matrix.build }} \
             -DCMAKE_CXX_COMPILER=${{ matrix.cxx }} \
             -DCMAKE_CUDA_COMPILER=${{ matrix.cxx }} \

CMakeLists.txt

@@ -520,7 +520,7 @@ endif()
 include(CheckIncludeFileCXX)
 if (CMAKE_SYSTEM_NAME STREQUAL "Darwin")
   CHECK_INCLUDE_FILE_CXX("dispatch/dispatch.h" STDEXEC_FOUND_LIBDISPATCH)
-  option(STDEXEC_ENABLE_LIBDISPATCH "Enable the tests for the Grand Central Dispatch scheduler" ${STDEXEC_FOUND_LIBDISPATCH})
+  option(STDEXEC_ENABLE_LIBDISPATCH "Enable use of the Grand Central Dispatch scheduler" ${STDEXEC_FOUND_LIBDISPATCH})
   target_compile_definitions(stdexec INTERFACE STDEXEC_ENABLE_LIBDISPATCH)
 endif()
 
@@ -567,7 +567,7 @@ else()
     "
     STDEXEC_FOUND_IO_URING)
 endif()
-option(STDEXEC_ENABLE_IO_URING_TESTS "Enable io_uring tests" ${STDEXEC_FOUND_IO_URING})
+option(STDEXEC_ENABLE_IO_URING "Enable the use of the io_uring scheduler on Linux" ${STDEXEC_FOUND_IO_URING})
 
 option(STDEXEC_BUILD_DOCS "Build stdexec documentation" OFF)
 option(STDEXEC_BUILD_EXAMPLES "Build stdexec examples" ON)

include/exec/__detail/__system_context_default_impl.hpp

@@ -18,9 +18,12 @@
 #include "__system_context_replaceability_api.hpp"
 
 #include "../../stdexec/execution.hpp"
-#include "../static_thread_pool.hpp"
 #if STDEXEC_ENABLE_LIBDISPATCH
 #  include "../libdispatch_queue.hpp" // IWYU pragma: keep
+#elif STDEXEC_ENABLE_IO_URING
+#  include "../linux/io_uring_context.hpp" // IWYU pragma: keep
+#else
+#  include "../static_thread_pool.hpp" // IWYU pragma: keep
 #endif
 
 #include <atomic>
@@ -365,6 +368,8 @@ namespace exec::__system_context_default_impl {
 
 #if STDEXEC_ENABLE_LIBDISPATCH
   using __parallel_scheduler_backend_impl = __generic_impl<exec::libdispatch_queue>;
+#elif STDEXEC_ENABLE_IO_URING
+  using __parallel_scheduler_backend_impl = __generic_impl<exec::io_uring_context>;
 #else
   using __parallel_scheduler_backend_impl = __generic_impl<exec::static_thread_pool>;
 #endif

test/exec/CMakeLists.txt

@@ -40,7 +40,7 @@ set(exec_test_sources
     test_when_any.cpp
     test_at_coroutine_exit.cpp
     test_materialize.cpp
-    $<$<BOOL:${STDEXEC_ENABLE_IO_URING_TESTS}>:test_io_uring_context.cpp>
+    $<$<BOOL:${STDEXEC_ENABLE_IO_URING}>:test_io_uring_context.cpp>
     test_trampoline_scheduler.cpp
     test_sequence_senders.cpp
     test_sequence.cpp