Effects: Attempts to obtain
shared lock ownership for the calling thread within the relative
timeout (
[thread.req.timing]) specified by
rel_time. If the time
specified by
rel_time is less than or equal to
rel_time.zero(),
the function attempts to obtain ownership without blocking (as if by calling
try_lock_shared())
. The function returns within the timeout
specified by
rel_time only if it has obtained shared ownership of the
mutex object
. [
Note 2:
As with
try_lock(), there is no guarantee that
ownership will be obtained if the lock is available, but implementations are
expected to make a strong effort to do so
. —
end note]
If an exception is thrown then a shared lock has not been acquired for
the current thread
.