any threads are created turned out to be not such a good idea.
there are stronger requirements on what has to work in a forked child
while a process is still single-threaded. so take all that stuff
back out and fix the problems with single-threaded programs that
are linked with libpthread differently, by checking if the library
has been started and doing completely different stuff if it hasn't been:
- for pthread_rwlock_timedrdlock(), just fail with EDEADLK immediately.
- for sem_wait(), the only thing that can unlock the semaphore is a
signal handler, so use sigsuspend() to wait for a signal.
- for pthread_mutex_lock_slow(), just go into an infinite loop
waiting for signals.
I also noticed that there's a "sem2" test that has never worked in its
single-threaded form. the problem there is that a signal handler tries
to take a sem_t interlock which is already held when the signal is received.
fix this too, by adding a single-threaded case for sig_trywait() that
blocks signals instead of using the userland interlock.
if the target thread is a zombie.
in all the functions that didn't do so already, verify a pthread_t before
dereferencing it (under #ifdef ERRORCHECK, since these checks are not
mandated by the standard).
clean up some debugging stuff.
call pthread__start() if it hasn't already been called. this avoids
an internal assertion from the library if these routines are used
before any threads are created and they need to sleep.
fixes PR 20256, PR 24241, PR 25722, PR 26096.
SCHED_OTHER happens to be 0, so this assignment to "int *" succeeds,
and becomes a no-op.
Fix by dereferencing "policy" to do the assignment, thus filling the
return buffer with 0.
setting a new signal action; this makes sigaction(sig, NULL, &oact)
return a sensible value in the signal mask instead of stack trash.
Addresses PR lib/29536.
XXX the mask seen by signal handlers in a program linked with
libpthread but not yet multithreaded will not reflect masks set here.
After exiting the try-again loop, make one more test of the lock
conditions, in case it was released while a signal handler kept the
thread busy past the alarm expiration.
blockgen!=unblockgen. I'm not sure this is 100% correct, but it partly
alleviates a problem with multiple unblocks for the same thread getting
stacked up.
a timer, as that will clear the timer instead. Pass in a safely in-the-past
value instead.
Addresses PR lib/28700.
(XXX passing in values between 0 and 1000 nanoseconds will still fail, but
that bug needs to be fixed in timer_settime(), not here)
scheduling stuff: only handle SCHED_OTHER. Like the rest of the scheduling
stuff, this is for the benefit of code that can't be bothered to test against
_POSIX_THREAD_PRIORITY_SCHEDULING.
pthread_cond_timedwait().
XXX as noted in the comments, in the situations where these are
useful, they should never be called in a single-threaded
process. Perhaps they should die rather than return 0.
Addresses xsrc/28630.
to be transformed into the do-nothing-when-libpthread-isn't-linked libc
stub names. This will permit library code that uses <pthread.h> and pthread
functions "defensively" to not need to link against libpthread and not need
to be patched to the threadlib.h API.
chs