Re: Test-lock hang (not 100% reproducible) on GNU/Linux

[Bruno Haible]

> and it points to two tests from the Linux test project [5][6]. Can you run
> these tests on your Koji system?

For me, these two tests fail on a glibc-2.23 system:

$ wget 
https://raw.githubusercontent.com/linux-test-project/ltp/master/testcases/open_posix_testsuite/conformance/interfaces/pthread_rwlock_rdlock/2-1.c
$ wget 
https://raw.githubusercontent.com/linux-test-project/ltp/master/testcases/open_posix_testsuite/conformance/interfaces/pthread_rwlock_rdlock/2-2.c
$ wget 
https://raw.githubusercontent.com/linux-test-project/ltp/master/testcases/open_posix_testsuite/include/posixtest.h
$ gcc -O -Wall 2-1.c -lpthread
$ ./a.out 
main: has priority: 3
main: attempt read lock
main: acquired read lock
main: create wr_thread, with priority: 2
wr_thread: attempt write lock
main: create rd_thread, with priority: 1
rd_thread: attempt read lock
rd_thread: acquired read lock
rd_thread: unlock read lock
Test FAILED: rd_thread did not block on read lock, when a reader owns the lock, 
and a higher priority writer is waiting for the lock
$ gcc -O -Wall 2-2.c -lpthread
$ ./a.out 
main: attempt read lock
main: acquired read lock
main: create wr_thread, with priority: 2
wr_thread: attempt write lock
main: create rd_thread, with priority: 2
rd_thread: attempt read lock
rd_thread: acquired read lock
rd_thread: unlock read lock
Test FAILED: rd_thread did not block on read lock, when a reader owns the lock, 
and an equal priority writer is waiting for the lock

In an 'ltrace' invocation, I see calls to pthread_rwlock_rdlock.
In an 'strace' invocation, I only see calls to futex, rt_sigaction,
rt_sigprocmask, which can be assumed to be correctly implemented.
So, the blame is clearly on glibc.

Bruno