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jabraham17jabraham17
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Backport Qthreads Fix For ppc64le (#27075)
The fast context swap is broken on little-endian ppc. This switches to using the fallback implementation from the system in that case. [Contributed by @insertinterestingnamehere, reviewed and merged by @jabraham17]
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‎third-party/qthread/README

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Original file line numberDiff line numberDiff line change
@@ -77,3 +77,36 @@ Prevent CMake from overriding the OSX deployment target
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set(THREADS_PREFER_PTHREAD_FLAG ON)
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Backport a patch from qthreads that switches to the fallback implementation of context swapping on ppc64le since the fast one is broken there.
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--- a/third-party/qthread/qthread-src/src/CMakeLists.txt
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+++ b/third-party/qthread/qthread-src/src/CMakeLists.txt
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@@ -8,7 +8,26 @@ set(QTHREADS_DEFAULT_STACK_SIZE 32768 CACHE STRING "Default qthread stack size."
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set(QTHREADS_HASHMAP hashmap CACHE STRING "Which hashmap implementation to use. Valid values are \"hashmap\" and \"lf_hashmap\".")
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set(QTHREADS_DICT_TYPE shavit CACHE STRING "Which dictionary implementation to use. Valid values are \"shavit\", \"trie\", and \"simple\".")
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set(QTHREADS_TIMER_TYPE gettimeofday CACHE STRING "Which timer implementation to use. Valid values are \"clock_gettime\", \"mach\", \"gettimeofday\", and \"gethrtime\".")
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-set(QTHREADS_CONTEXT_SWAP_IMPL fastcontext CACHE STRING "Which context swap implementation to use. Valid values are \"system\" and \"fastcontext\".")
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+# Only default to the fastcontext implementation in cases where it's confirmed to work.
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+# Note: apparently 32-bit x86 may show up as i386, i486, i586, or i686.
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+# Little-endian powerpc variants are excluded here as they're known not to work
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+# due to an unresolved bug in our fastcontext code.
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+if ("${CMAKE_SYSTEM_PROCESSOR}" STREQUAL "x86_64" OR
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+ "${CMAKE_SYSTEM_PROCESSOR}" STREQUAL "amd64" OR
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+ "${CMAKE_SYSTEM_PROCESSOR}" STREQUAL "aarch64" OR
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+ "${CMAKE_SYSTEM_PROCESSOR}" STREQUAL "arm64" OR
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+ "${CMAKE_SYSTEM_PROCESSOR}" STREQUAL "arm" OR
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+ "${CMAKE_SYSTEM_PROCESSOR}" STREQUAL "i386" OR
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+ "${CMAKE_SYSTEM_PROCESSOR}" STREQUAL "i486" OR
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+ "${CMAKE_SYSTEM_PROCESSOR}" STREQUAL "i586" OR
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+ "${CMAKE_SYSTEM_PROCESSOR}" STREQUAL "i686" OR
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+ "${CMAKE_SYSTEM_PROCESSOR}" STREQUAL "ppc64" OR
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+ "${CMAKE_SYSTEM_PROCESSOR}" STREQUAL "ppc")
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+ set(QTHREADS_CONTEXT_SWAP_IMPL fastcontext CACHE STRING "Which context swap implementation to use. Valid values are \"system\" and \"fastcontext\".")
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+else()
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+ message(WARNING "No fast context swap available on this system, falling back to the system-provided one.")
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+ set(QTHREADS_CONTEXT_SWAP_IMPL system CACHE STRING "Which context swap implementation to use. Valid values are \"system\" and \"fastcontext\".")
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+endif()
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set(QTHREADS_HWLOC_GET_TOPOLOGY_FUNCTION "" CACHE STRING "function to get hwloc topology (otherwise uses hwloc_topology_init and hwloc_topology_load)")
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set(QTHREADS_GUARD_PAGES OFF CACHE BOOL "Whether or not to guard memory pages to help with debugging stack overflows. Default is OFF.")
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set(QTHREADS_CONDWAIT_QUEUE OFF CACHE BOOL "Use a waiting queue based on pthread condition variables instead of a spin-based queue for inter-thread communication. Default is OFF.")
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‎third-party/qthread/qthread-src/src/CMakeLists.txt

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Original file line numberDiff line numberDiff line change
@@ -8,7 +8,26 @@ set(QTHREADS_DEFAULT_STACK_SIZE 32768 CACHE STRING "Default qthread stack size."
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set(QTHREADS_HASHMAP hashmap CACHE STRING "Which hashmap implementation to use. Valid values are \"hashmap\" and \"lf_hashmap\".")
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set(QTHREADS_DICT_TYPE shavit CACHE STRING "Which dictionary implementation to use. Valid values are \"shavit\", \"trie\", and \"simple\".")
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set(QTHREADS_TIMER_TYPE gettimeofday CACHE STRING "Which timer implementation to use. Valid values are \"clock_gettime\", \"mach\", \"gettimeofday\", and \"gethrtime\".")
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set(QTHREADS_CONTEXT_SWAP_IMPL fastcontext CACHE STRING "Which context swap implementation to use. Valid values are \"system\" and \"fastcontext\".")
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# Only default to the fastcontext implementation in cases where it's confirmed to work.
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# Note: apparently 32-bit x86 may show up as i386, i486, i586, or i686.
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# Little-endian powerpc variants are excluded here as they're known not to work
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# due to an unresolved bug in our fastcontext code.
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if ("${CMAKE_SYSTEM_PROCESSOR}" STREQUAL "x86_64" OR
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"${CMAKE_SYSTEM_PROCESSOR}" STREQUAL "amd64" OR
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"${CMAKE_SYSTEM_PROCESSOR}" STREQUAL "aarch64" OR
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"${CMAKE_SYSTEM_PROCESSOR}" STREQUAL "arm64" OR
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"${CMAKE_SYSTEM_PROCESSOR}" STREQUAL "arm" OR
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"${CMAKE_SYSTEM_PROCESSOR}" STREQUAL "i386" OR
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"${CMAKE_SYSTEM_PROCESSOR}" STREQUAL "i486" OR
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"${CMAKE_SYSTEM_PROCESSOR}" STREQUAL "i586" OR
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"${CMAKE_SYSTEM_PROCESSOR}" STREQUAL "i686" OR
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"${CMAKE_SYSTEM_PROCESSOR}" STREQUAL "ppc64" OR
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"${CMAKE_SYSTEM_PROCESSOR}" STREQUAL "ppc")
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set(QTHREADS_CONTEXT_SWAP_IMPL fastcontext CACHE STRING "Which context swap implementation to use. Valid values are \"system\" and \"fastcontext\".")
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else()
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message(WARNING "No fast context swap available on this system, falling back to the system-provided one.")
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set(QTHREADS_CONTEXT_SWAP_IMPL system CACHE STRING "Which context swap implementation to use. Valid values are \"system\" and \"fastcontext\".")
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endif()
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set(QTHREADS_HWLOC_GET_TOPOLOGY_FUNCTION "" CACHE STRING "function to get hwloc topology (otherwise uses hwloc_topology_init and hwloc_topology_load)")
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set(QTHREADS_GUARD_PAGES OFF CACHE BOOL "Whether or not to guard memory pages to help with debugging stack overflows. Default is OFF.")
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set(QTHREADS_CONDWAIT_QUEUE OFF CACHE BOOL "Use a waiting queue based on pthread condition variables instead of a spin-based queue for inter-thread communication. Default is OFF.")

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