[Openmp-commits] [openmp] 94232f9 - [OpenMP][OMPT] Use global thread id for `codeptr_ra` in `end_critical` (#169826)

[via Openmp-commits]

Author: Jan André Reuter
Date: 2025-12-03T19:03:34+01:00
New Revision: 94232f9f560f84d2ae7f50b2d1df5bc26b2ce69e

URL: https://github.com/llvm/llvm-project/commit/94232f9f560f84d2ae7f50b2d1df5bc26b2ce69e
DIFF: https://github.com/llvm/llvm-project/commit/94232f9f560f84d2ae7f50b2d1df5bc26b2ce69e.diff

LOG: [OpenMP][OMPT] Use global thread id for `codeptr_ra` in `end_critical` (#169826)

When a critical construct has finished, it will trigger a
critical-released event. If a tool is attached, and the `mutex_released`
callback was registered, the tool with receive an event containing the
`codeptr_ra`, the return address of the callback invocation.

All the way back in 82e94a593433f36734e2d34898d353a2ecb65b8b, this
`codeptr_ra` was implemented by calling `__ompt_load_return_address`
with a fixed global thread id of `0`. However, this approach results in
a race-condition, and can yield incorrect results to the tool.

`__ompt_load_return_address(0)` points to the current return address of
the thread 0 in `__kmp_threads`. This thread may already execute some
other construct. A tool might therefore receive the return address of
e.g. some `libomp` internals, or other parts of the user code.
Additionally, a call to `__ompt_load_return_address` resets the
`th.ompt_thread_info.return_address` to `NULL`, therefore also affecting
the return address of thread 0. Another dispatched event, e.g.
parallel-begin might therefore not transfer any `codeptr_ra`.

To fix this, replace the fixed thread id by the `global_tid`, which is
stored just before dispatching the `mutex_released` callback.

Signed-off-by: Jan André Reuter <j.reuter at fz-juelich.de>

Added: 
    

Modified: 
    openmp/runtime/src/kmp_csupport.cpp

Removed: 
    


################################################################################
diff  --git a/openmp/runtime/src/kmp_csupport.cpp b/openmp/runtime/src/kmp_csupport.cpp
index 3ca32ba583fe2..a92fc46374c27 100644
--- a/openmp/runtime/src/kmp_csupport.cpp
+++ b/openmp/runtime/src/kmp_csupport.cpp
@@ -1780,7 +1780,7 @@ void __kmpc_end_critical(ident_t *loc, kmp_int32 global_tid,
   if (ompt_enabled.ompt_callback_mutex_released) {
     ompt_callbacks.ompt_callback(ompt_callback_mutex_released)(
         ompt_mutex_critical, (ompt_wait_id_t)(uintptr_t)lck,
-        OMPT_LOAD_RETURN_ADDRESS(0));
+        OMPT_LOAD_RETURN_ADDRESS(global_tid));
   }
 #endif