even a single-threaded program can be cancellable, e.g. if it's called
pthread_cancel(pthread_self()). the correct predicate to check is not
whether multiple threads have been invoked, but whether pthread_self
has been invoked.
this fixes an issue using gold instead of gnu ld for linking. it also
should eliminate the need of the startup code to even load/pass the
got address to the dynamic linker.
based on patch submitted by sh4rm4 with minor cosmetic changes.
further cleanup will follow.
note that regardless of the name used, basename is always conformant.
it never takes on the bogus gnu behavior, unlike glibc where basename
is nonconformant when declared manually without including libgen.h.
CHUNK_SIZE macro was defined incorrectly and shaving off at least one
significant bit in the size of mmapped chunks, resulting in the test
for oldlen==newlen always failing and incurring a syscall. fortunately
i don't think this issue caused any other observable behavior; the
definition worked correctly for all non-mmapped chunks where its
correctness matters more, since their lengths are always multiples of
the alignment.
musl's dynamic linker does not support unloading dsos, so there's
nothing for this function to do. adding the symbol in case anything
depends on its presence..
the fcntl syscall can return a negative value when the command is
F_GETOWN, and this is not an error code but an actual value. thus we
must special-case it and avoid calling __syscall_ret to set errno.
this fix is better than the glibc fix (using F_GETOWN_EX) which only
works on newer kernels and is more complex.
right now it's questionable whether this change is an improvement or
not, but if we later want to support priority inheritance mutexes, it
will be important to have the code paths unified like this to avoid
major code duplication.
this simplifies the code paths slightly, but perhaps what's nicer is
that it makes recursive mutexes fully reentrant, i.e. locking and
unlocking from a signal handler works even if the interrupted code was
in the middle of locking or unlocking.
a reader unlocking the lock need only wake one waiter (necessarily a
writer, but a writer unlocking the lock must wake all waiters
(necessarily readers). if it only wakes one, the remainder can remain
blocked indefinitely, or at least until the first reader unlocks (in
which case the whole lock becomes serialized and behaves as a mutex
rather than a read lock).
there is no need to send a wake when the lock count does not hit zero,
but when it does, all waiters must be woken (since all with the same
sign are eligible to obtain the lock).
eliminate the sequence number field and instead use the counter as the
futex because of the way the lock is held, sequence numbers are
completely useless, and this frees up a field in the barrier structure
to be used as a waiter count for the count futex, which lets us avoid
some syscalls in the best case.
as of now, self-synchronized destruction and unmapping should be fully
safe. before any thread can return from the barrier, all threads in
the barrier have obtained the vm lock, and each holds a shared lock on
the barrier. the barrier memory is not inspected after the shared lock
count reaches 0, nor after the vm lock is released.
it was assuming the result of the condition it was supposed to be
checking for, i.e. that the thread ptr had already been initialized by
pthread_mutex_lock. use the slower call to be safe.
we're not required to check this except for error-checking mutexes,
but it doesn't hurt. the new test is actually simpler/lighter, and it
also eliminates the need to later check that pthread_mutex_unlock
succeeds.
when used with error-checking mutexes, pthread_cond_wait is required
to fail with EPERM if the mutex is not locked by the caller.
previously we relied on pthread_mutex_unlock to generate the error,
but this is not valid, since in the case of such invalid usage the
internal state of the cond variable has already been potentially
corrupted (due to access outside the control of the mutex). thus, we
have to check first.
Rich Felker