Implement pthread_mutex_clocklock(3) and pthread_rwlock_clock{wr,rd}lock(3) from POSIX 2024

[kib]

Summary

kern_umtx.c: validate clockid used for _umtx_op(2) timeouts

Only allow clocks that make sense for the umtx_sleep().

While there, do not ignore errors from kern_clock_gettime(). The invalid
clock ids are filtered, but if the clock can't be read (CLOCK_TAI before
the TAI-UTC offset is known), the functions operate on uninitialized
memory.


_umtx_op.2: correct the description of the valid _clockid for _umtx_time

And remove the duplicated list from the description of the condition
variable.


umtxq_sleep(): do not wait forever for zero absolute timeouts

For msleep(), zero sbt means no timeout. If the timeout was specified as
absolute {0, 0} on MONOTONIC/UPTIME clocks, consider the call timed out
immediately, instead of sleeping until a signal is delivered.


lib/libthr: add helper to check valid clockid to use with _umtx_op(2)


pthread_cond_clockwait(3): explicitly reject unacceptable clockids

Otherwise they are rejected by kernel in do_wait(), reached through
_thr_sleep()/UMTX_OP_WAIT_UINT_PRIVATE on the user-mode path. Then,
since cond_wait_user() only leaves its loop on a wakeup, a cancellation
or ETIMEDOUT, the EINVAL from do_wait() results in a loop.

If hit, this indicates a bug in user code, but the system library
must be resilient to such misuse.


libthr cond_wait_user(): do not loop forever on clock error


pthread_mutex_timedlock(3): return EDEADLK on detected recursion attempt

for ERRORCHECK and ADAPTIVE_NP mutexes, instead of ETIMEDOUT. This is
explicitly specified by POSIX.


libthr: add pthread_mutex_clocklock(3)


libthr: add pthread_rwlock_clock{rd,wr}lock(3)


pthread_cond_timedwait.3: list pthread_cond_clockwait as .Nm


pthread_*_timed*lock.3: switch to .Fo/Fc


pthread_mutex_clocklock.3: document


pthread_rwlock_clock{rd,wr}lock(3): document


pthread_cond_timedwait.3: split STANDARDS and HISTORY

[kib]

I will add tests later.