[compiler-rt] Fix race in the implementation of __tsan_acquire() (PR #84923)

[Dave Clausen via llvm-commits]

https://github.com/daveclausen commented:

It doesn't show up in the list of slowest tests:

```
$ LIT_OPTS="--time-tests" ninja check-tsan

...

Slowest Tests:
--------------------------------------------------------------------------
45.32s: ThreadSanitizer-x86_64 :: restore_stack.cpp
33.56s: ThreadSanitizer-x86_64 :: Linux/check_memcpy.c
21.56s: ThreadSanitizer-x86_64 :: bench_threads.cpp
14.70s: ThreadSanitizer-x86_64 :: deadlock_detector_stress_test.cpp
14.65s: ThreadSanitizer-x86_64 :: signal_thread.cpp
12.60s: ThreadSanitizer-x86_64 :: stress.cpp
10.81s: ThreadSanitizer-x86_64 :: Linux/fork_multithreaded4.cpp
9.79s: ThreadSanitizer-x86_64 :: force_background_thread.cpp
9.53s: ThreadSanitizer-x86_64 :: lots_of_threads.c
7.14s: ThreadSanitizer-x86_64 :: deep_stack1.cpp
5.73s: ThreadSanitizer-x86_64 :: fd_close_norace3.cpp
5.40s: ThreadSanitizer-x86_64 :: signal_reset.cpp
5.19s: ThreadSanitizer-x86_64 :: mmap_stress.cpp
4.84s: ThreadSanitizer-x86_64 :: signal_sync2.cpp
4.48s: ThreadSanitizer-x86_64 :: global_race.cpp
4.41s: ThreadSanitizer-x86_64 :: ignore_lib6.cpp
3.65s: ThreadSanitizer-x86_64 :: mmap_stress2.cpp
3.51s: ThreadSanitizer-x86_64 :: must_deadlock.cpp
3.51s: ThreadSanitizer-x86_64 :: simple_stack.c
3.50s: ThreadSanitizer-x86_64 :: setuid2.c

Tests Times:
--------------------------------------------------------------------------
[    Range    ] :: [               Percentage               ] :: [ Count ]
--------------------------------------------------------------------------
[44.0s,46.0s) :: [                                        ] :: [  1/409]
[42.0s,44.0s) :: [                                        ] :: [  0/409]
[40.0s,42.0s) :: [                                        ] :: [  0/409]
[38.0s,40.0s) :: [                                        ] :: [  0/409]
[36.0s,38.0s) :: [                                        ] :: [  0/409]
[34.0s,36.0s) :: [                                        ] :: [  1/409]
[32.0s,34.0s) :: [                                        ] :: [  0/409]
[30.0s,32.0s) :: [                                        ] :: [  0/409]
[28.0s,30.0s) :: [                                        ] :: [  0/409]
[26.0s,28.0s) :: [                                        ] :: [  0/409]
[24.0s,26.0s) :: [                                        ] :: [  0/409]
[22.0s,24.0s) :: [                                        ] :: [  0/409]
[20.0s,22.0s) :: [                                        ] :: [  1/409]
[18.0s,20.0s) :: [                                        ] :: [  0/409]
[16.0s,18.0s) :: [                                        ] :: [  0/409]
[14.0s,16.0s) :: [                                        ] :: [  2/409]
[12.0s,14.0s) :: [                                        ] :: [  1/409]
[10.0s,12.0s) :: [                                        ] :: [  1/409]
[ 8.0s,10.0s) :: [                                        ] :: [  2/409]
[ 6.0s, 8.0s) :: [                                        ] :: [  1/409]
[ 4.0s, 6.0s) :: [                                        ] :: [  6/409]
[ 2.0s, 4.0s) :: [*                                       ] :: [ 16/409]
[ 0.0s, 2.0s) :: [************************************    ] :: [377/409]
--------------------------------------------------------------------------

Testing Time: 45.37s

Total Discovered Tests: 451
  Unsupported      :  88 (19.51%)
  Passed           : 362 (80.27%)
  Expectedly Failed:   1 (0.22%)
```


https://github.com/llvm/llvm-project/pull/84923