forked from OSchip/llvm-project
f41d08540b
__ompt_get_task_info_internal function is adapted to support thread_num determination during the execution of multiple nested serialized parallel regions enclosed by a regular parallel region. Consider the following program that contains parallel region R1 executed by two threads. Let the worker thread T of region R1 executes serialized parallel regions R2 that encloses another serialized parallel region R3. Note that the thread T is the master thread of both R2 and R3 regions. Assume that __ompt_get_task_info_internal function is called with the argument "ancestor_level == 1" during the execution of region R3. The function should determine the "thread_num" of the thread T inside the team of region R2, whose implicit task is at level 1 inside the hierarchy of active tasks. Since the thread T is the master thread of region R2, one should expected that "thread_num" takes a value 0. After the while loop finishes, the following stands: "lwt != NULL", "prev_lwt == NULL", "prev_team" represents the team information about the innermost serialized parallel region R3. This results in executing the assignment "thread_num = prev_team->t.t_master_tid". Note that "prev_team->t.t_master_tid" was initialized at the moment of R2’s creation and represents the "thread_num" of the thread T inside the region R1 which encloses R2. Since the thread T is the worker thread of the region R1, "the thread_num" takes value 1, which is a contradiction. This patch proposes to use "lwt" instead of "prev_lwt" when determining the "thread_num". If "lwt" exists, the task at the requested level belongs to the serialized parallel region. Since the serialized parallel region is executed by one thread only, the "thread_num" takes value 0. Similarly, assume that __ompt_get_task_info_internal function is called with the argument "ancestor_level == 2" during the execution of region R3. The function should determine the "thread_num" of the thread T inside the team of region R1. Since the thread is the worker inside the region R1, one should expected that "thread_num" takes value 1. After the loop finishes, the following stands: "lwt == NULL", "prev_lwt != NULL", "prev_team" represents the team information about the innermost serialized parallel region R3. This leads to execution of the assignment "thread_num = 0", which causes a contradiction. Ignoring the "prev_lwt" leads to executing the assignment "thread_num = prev_team->t.t_master_tid" instead. From the previous explanation, it is obvious that "thread_num" takes value 1. Note that the "prev_lwt" variable is marked as unnecessary and thus removed. This patch introduces the test case which represents the OpenMP program described earlier in the summary. Differential Revision: https://reviews.llvm.org/D110699 |
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| .. | ||
| dynamic_enough_threads.c | ||
| dynamic_not_enough_threads.c | ||
| max_active_levels_serialized.c | ||
| nested.c | ||
| nested_lwt.c | ||
| nested_lwt_thread_num.c | ||
| nested_serialized.c | ||
| nested_serialized_task_frames.c | ||
| nested_thread_num.c | ||
| nested_threadnum.c | ||
| no_thread_num_clause.c | ||
| normal.c | ||
| not_enough_threads.c | ||
| parallel_if0.c | ||
| region_in_expl_task_task_frames.c | ||
| repeated_calls.c | ||
| serialized.c | ||