[llvm-bugs] [Bug 51235] New: Tasking regression tests take 21mins

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=51235

            Bug ID: 51235
           Summary: Tasking regression tests take 21mins
           Product: OpenMP
           Version: unspecified
          Hardware: PC
                OS: Windows NT
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: Runtime Library
          Assignee: unassignedbugs at nondot.org
          Reporter: llvm at meinersbur.de
                CC: llvm-bugs at lists.llvm.org

Execution time of the regression test have increased significantly from 1m20s
to ~21m. I am suspecting the following change to be responsible:
https://reviews.llvm.org/D106572

Buildbot first occuring builds:
openmp-offload-cuda-runtime:
https://lab.llvm.org/staging/#/builders/154/builds/1717
openmp-offload-cuda-project:
https://lab.llvm.org/staging/#/builders/155/builds/2196 (Build #2195 introduced
D106572)

Some tasking tests such as depend.cpp or gtid.cpp indeterministically take a
long time to complete without showing up as failed tests. In htop all threads
except one show up as busy-waiting with one in an interruptible sleep.

Attaching gdb to the test gtid showed the following stack traces:

Thread 7 (Thread 0x7fe945ae6700 (LWP 2647011)):
#0  futex_wait_cancelable (private=<optimized out>, expected=0,
futex_word=0x7fe948635868 <(anonymous
namespace)::hidden_helper_main_thread_cond_var+40>) at
../sysdeps/nptl/futex-internal.h:183
#1  __pthread_cond_wait_common (abstime=0x0, clockid=0, mutex=0x7fe948635800
<(anonymous namespace)::hidden_helper_main_thread_lock>, cond=0x7fe948635840
<(anonymous namespace)::hidden_helper_main_thread_cond_var>) at
pthread_cond_wait.c:508
#2  __pthread_cond_wait (cond=0x7fe948635840 <(anonymous
namespace)::hidden_helper_main_thread_cond_var>, mutex=0x7fe948635800
<(anonymous namespace)::hidden_helper_main_thread_lock>) at
pthread_cond_wait.c:638
#3  0x00007fe94860569b in __kmp_hidden_helper_main_thread_wait () from
/home/buildbot-worker/minipc-1050ti-linux/openmp-offload-cuda-project/llvm.build/lib/libomp.so
#4  0x00007fe9485a1ce4 in (anonymous
namespace)::__kmp_hidden_helper_wrapper_fn(int*, int*, ...) () from
/home/buildbot-worker/minipc-1050ti-linux/openmp-offload-cuda-project/llvm.build/lib/libomp.so
#5  0x00007fe94861eee3 in __kmp_invoke_microtask () from
/home/buildbot-worker/minipc-1050ti-linux/openmp-offload-cuda-project/llvm.build/lib/libomp.so
#6  0x00007fe9485a1aa1 in __kmp_invoke_task_func () from
/home/buildbot-worker/minipc-1050ti-linux/openmp-offload-cuda-project/llvm.build/lib/libomp.so
#7  0x00007fe9485abe6e in __kmp_fork_call () from
/home/buildbot-worker/minipc-1050ti-linux/openmp-offload-cuda-project/llvm.build/lib/libomp.so
#8  0x00007fe948596df7 in __kmpc_fork_call () from
/home/buildbot-worker/minipc-1050ti-linux/openmp-offload-cuda-project/llvm.build/lib/libomp.so
--Type <RET> for more, q to quit, c to continue without paging--
#9  0x00007fe9485aa764 in __kmp_hidden_helper_threads_initz_routine () from
/home/buildbot-worker/minipc-1050ti-linux/openmp-offload-cuda-project/llvm.build/lib/libomp.so
#10 0x00007fe948601afd in
__kmp_do_initialize_hidden_helper_threads::{lambda(void*)#1}::_FUN(void*) ()
from
/home/buildbot-worker/minipc-1050ti-linux/openmp-offload-cuda-project/llvm.build/lib/libomp.so
#11 0x00007fe948503609 in start_thread (arg=<optimized out>) at
pthread_create.c:477
#12 0x00007fe948428293 in clone () at
../sysdeps/unix/sysv/linux/x86_64/clone.S:95

Thread 8 (Thread 0x7fe9452e4800 (LWP 2647012)):
#0  0x00007fe94840b89b in sched_yield () at
../sysdeps/unix/syscall-template.S:78
#1  0x00007fe9485ce08a in bool __kmp_wait_template<kmp_flag_64<false, true>,
true, false, true>(kmp_info*, kmp_flag_64<false, true>*, void*) [clone
.constprop.0] () from
/home/buildbot-worker/minipc-1050ti-linux/openmp-offload-cuda-project/llvm.build/lib/libomp.so
#2  0x00007fe9485d7a7f in __kmp_fork_barrier(int, int) () from
/home/buildbot-worker/minipc-1050ti-linux/openmp-offload-cuda-project/llvm.build/lib/libomp.so
#3  0x00007fe9485a66b5 in __kmp_launch_thread () from
/home/buildbot-worker/minipc-1050ti-linux/openmp-offload-cuda-project/llvm.build/lib/libomp.so
#4  0x00007fe948601d57 in __kmp_launch_worker(void*) () from
/home/buildbot-worker/minipc-1050ti-linux/openmp-offload-cuda-project/llvm.build/lib/libomp.so
#5  0x00007fe948503609 in start_thread (arg=<optimized out>) at
pthread_create.c:477
#6  0x00007fe948428293 in clone () at
../sysdeps/unix/sysv/linux/x86_64/clone.S:95
[repeated for all other threads]

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