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191fd0f9e5
While testing an OpenCL driver with ThreadSanitizer enabled the
OpenCL-CTS suffers from thread leaks in conversions and bruteforce on
posix systems. This is because `pthread_join` is never called in
`ThreadPool_Exit` for the `pthread_t`s created by the thread pool.
Instead, the threads are only informed to stop waiting on the condition
variable which unblocks the worker thread but does not clean up after
itself.
```
ThreadPool: thread 1 exiting.
ThreadPool: thread 5 exiting.
ThreadPool: thread 4 exiting.
ThreadPool: thread 2 exiting.
ThreadPool: thread 7 exiting.
ThreadPool: thread 0 exiting.
ThreadPool: thread 3 exiting.
ThreadPool: thread 6 exiting.
Thread pool exited in a orderly fashion.
==================
WARNING: ThreadSanitizer: thread leak (pid=2292842)
Thread T9 (tid=2292855, finished) created by main thread at:
#0 pthread_create ../../../../src/libsanitizer/tsan/tsan_interceptors_posix.cpp:969 (libtsan.so.0+0x5ad75)
#1 ThreadPool_Init() <null> (test_conversions+0x35b2c)
#2 pthread_once ../../../../src/libsanitizer/tsan/tsan_interceptors_posix.cpp:1449 (libtsan.so.0+0x4057c)
#3 GetThreadCount() <null> (test_conversions+0x36262)
#4 DoTest(_cl_device_id*, Type, Type, SaturationMode, RoundingMode, _MTdata*) [clone .isra.0] <null> (test_conversions+0x10555)
#5 test_conversions(_cl_device_id*, _cl_context*, _cl_command_queue*, int) <null> (test_conversions+0x13226)
#6 callSingleTestFunction(test_definition, _cl_device_id*, int, int, unsigned long) <null> (test_conversions+0x2e66d)
#7 parseAndCallCommandLineTests(int, char const**, _cl_device_id*, int, test_definition*, int, unsigned long, int) <null> (test_conversions+0x2fb3a)
#8 runTestHarnessWithCheck(int, char const**, int, test_definition*, int, unsigned long, test_status (*)(_cl_device_id*)) <null> (test_conversions+0x349d8)
#9 main <null> (test_conversions+0xd725)
And 7 more similar thread leaks.
SUMMARY: ThreadSanitizer: thread leak (OpenCL-CTS/buildbin/conversions/test_conversions+0x35b2c) in ThreadPool_Init()
```
This patch adds global state to keep track of the `pthread_t`s created
by `pthread_create` in `ThreadPool_Init`. The list of `pthread_t`s is
then used by `ThreadPool_Exit` to call `pthread_join` to cleanup the
`pthread_t`s correctly.
A near identical example, and additional explanation, can be found on
[stackoverflow](https://stackoverflow.com/questions/72435574/thread-leak-detected-when-using-condition-variable-instead-of-join-with-pthrea).
On the Windows path, a similar change is not necessary because
`_beginthread` is used which automatically cleans up after itself when
the worker thread function returns.