Fixes for integration tests of sem_syscalls

[yashaswi2000]

Description

This is a fix for [#248] issue. where we see intermittent test failures which uses semaphores. and performs actions like

• sem_wait
• sem_post
• sem_timed_wait
• sem_try_wait

The tests effected are:

• ut_lind_fs_sem_fork()
• ut_lind_fs_sem_trytimed()
• ut_lind_fs_sem_test()

Causes:

• The first kind of issue was assertion failures when sem_getvalue_syscall is performed outside of the critical section of parent/child process. which causes nondeterministic outputs since once out of critical section the busy waiting thread/process will go into its critical section and modify the semaphore value.

• The second type is performing sem_try_wait call to enter into critical section, and always asserting a success from the call. sem_try_wait is different from sem_wait in the sense there is no busy waiting and thus if another thread/process is in the critical section, it just returns false.

• The third kind of issue is performing sem_destroy before the child process exits its critical section. which causes nondeterministic behaviour, leading to child's sem_post call to throw error. parent process has to wait for all the threads/process to exit before destroying semaphore and shared memory.

Fixes # (issue)

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

How Has This Been Tested?

• Test A - lind_project/tests/test_cases/test_a.c
• Test B - lind_project/tests/test_cases/test_b.c

Checklist:

• My code follows the style guidelines of this project
• I have commented my code, particularly in hard-to-understand areas
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• Any dependent changes have been added to a pull request and/or merged in other modules (native-client, lind-glibc, lind-project)

[JustinCappos]

Do you need to do this cleanup or does the exit syscall do it? It might be useful to say either way in the comments here...

[JustinCappos]

Looks good to me!