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[MrBot] Add robust_semaphore, a cross-process semaphore that survives holder crashes #655

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[MrBot] Add robust_semaphore, a cross-process semaphore that survives holder crashes #655

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14d9468
Add robust_semaphore, a named cross-process semaphore made of mutexes…
dcristoloveanu Oct 21, 2026
ff2e628
Document that cancel and release cannot take back a unit acquired con…
dcristoloveanu Oct 21, 2026
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2 changes: 2 additions & 0 deletions win32/CMakeLists.txt
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Original file line number Diff line number Diff line change
Expand Up @@ -40,6 +40,7 @@ set(pal_win32_h_files
${pal_common_h_files}
inc/c_pal/execution_engine_win32.h
inc/c_pal/job_object_helper.h
inc/c_pal/robust_semaphore.h
)

set(pal_win32_c_files
Expand All @@ -64,6 +65,7 @@ set(pal_win32_c_files
src/${gballoc_ll_c}
src/${gballoc_hl_c}
src/job_object_helper.c
src/robust_semaphore.c
)

FILE(GLOB pal_win32_md_files "devdoc/*.md")
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224 changes: 224 additions & 0 deletions win32/devdoc/robust_semaphore_requirements.md
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50 changes: 50 additions & 0 deletions win32/inc/c_pal/robust_semaphore.h
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Original file line number Diff line number Diff line change
@@ -0,0 +1,50 @@
// Copyright (c) Microsoft. All rights reserved.
// Licensed under the MIT license. See LICENSE file in the project root for full license information.

#ifndef ROBUST_SEMAPHORE_H
#define ROBUST_SEMAPHORE_H

#ifdef __cplusplus
#include <cstdint>
#else
#include <stdint.h>
#endif

#include "macro_utils/macro_utils.h"

#include "umock_c/umock_c_prod.h"

/* a robust semaphore with N units is made of N mutexes, waited on together with the cancel event (MAXIMUM_WAIT_OBJECTS is 64) */
#define ROBUST_SEMAPHORE_MAX_COUNT 63

/* wait for a unit until one is free / hold a unit with no time limit */
#define ROBUST_SEMAPHORE_NO_TIMEOUT UINT32_MAX

#define ROBUST_SEMAPHORE_UNIT_INDEX_NONE UINT32_MAX

#define ROBUST_SEMAPHORE_ACQUIRE_RESULT_VALUES \
ROBUST_SEMAPHORE_ACQUIRE_OK, \
ROBUST_SEMAPHORE_ACQUIRE_TIMEOUT, \
ROBUST_SEMAPHORE_ACQUIRE_CANCELLED, \
ROBUST_SEMAPHORE_ACQUIRE_ERROR

MU_DEFINE_ENUM(ROBUST_SEMAPHORE_ACQUIRE_RESULT, ROBUST_SEMAPHORE_ACQUIRE_RESULT_VALUES);

typedef struct ROBUST_SEMAPHORE_TAG* ROBUST_SEMAPHORE_HANDLE;

typedef void (*ROBUST_SEMAPHORE_ON_ACQUIRE_COMPLETE)(void* context, ROBUST_SEMAPHORE_ACQUIRE_RESULT result, uint32_t unit_index);

#ifdef __cplusplus
extern "C"
{
#endif
MOCKABLE_FUNCTION(, ROBUST_SEMAPHORE_HANDLE, robust_semaphore_create, const char*, name, uint32_t, max_count, const char*, security_descriptor);
MOCKABLE_FUNCTION(, void, robust_semaphore_destroy, ROBUST_SEMAPHORE_HANDLE, robust_semaphore);
MOCKABLE_FUNCTION(, int, robust_semaphore_acquire_async, ROBUST_SEMAPHORE_HANDLE, robust_semaphore, uint32_t, timeout_ms, uint32_t, max_hold_ms, ROBUST_SEMAPHORE_ON_ACQUIRE_COMPLETE, on_acquire_complete, void*, on_acquire_complete_context);
MOCKABLE_FUNCTION(, void, robust_semaphore_cancel, ROBUST_SEMAPHORE_HANDLE, robust_semaphore);
MOCKABLE_FUNCTION(, void, robust_semaphore_release, ROBUST_SEMAPHORE_HANDLE, robust_semaphore);
#ifdef __cplusplus
}
#endif

#endif // ROBUST_SEMAPHORE_H
712 changes: 712 additions & 0 deletions win32/src/robust_semaphore.c
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3 changes: 3 additions & 0 deletions win32/tests/CMakeLists.txt
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Original file line number Diff line number Diff line change
Expand Up @@ -35,15 +35,18 @@ if(${run_unittests})

build_test_folder(gballoc_hl_passthrough_ut)
build_test_folder(job_object_helper_ut)
build_test_folder(robust_semaphore_ut)
endif()

if(${run_int_tests})
add_subdirectory(job_object_helper_tester)
add_subdirectory(process_watchdog_int_child)
add_subdirectory(robust_semaphore_tester)
build_test_folder(malloc_multi_flex_int)
build_test_folder(string_utils_int)
build_test_folder(job_object_helper_int)
build_test_folder(process_watchdog_int)
build_test_folder(robust_semaphore_int)

if((${GBALLOC_LL_TYPE} STREQUAL "MIMALLOC"))
build_test_folder(gballoc_ll_mimalloc_int)
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24 changes: 24 additions & 0 deletions win32/tests/robust_semaphore_int/CMakeLists.txt
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@@ -0,0 +1,24 @@
#Copyright (c) Microsoft. All rights reserved.
#Licensed under the MIT license. See LICENSE file in the project root for full license information.

set(theseTestsName robust_semaphore_int)

set(${theseTestsName}_test_files
${theseTestsName}.c
)

set(${theseTestsName}_c_files
)

set(${theseTestsName}_h_files
)

build_test_artifacts(${theseTestsName} "tests/c_pal/win32" ADDITIONAL_LIBS c_pal)

# the tests start robust_semaphore_tester to hold a unit from another process
if(TARGET ${theseTestsName}_exe_${CMAKE_PROJECT_NAME})
add_dependencies(${theseTestsName}_exe_${CMAKE_PROJECT_NAME} robust_semaphore_tester)
endif()
if(TARGET ${theseTestsName}_dll_${CMAKE_PROJECT_NAME})
add_dependencies(${theseTestsName}_dll_${CMAKE_PROJECT_NAME} robust_semaphore_tester)
endif()
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