CVS commit: src/sys

["Taylor R Campbell" <riastradh%netbsd.org@localhost>]

Module Name:    src
Committed By:   riastradh
Date:           Sun May  3 01:24:38 UTC 2020

Modified Files:
        src/sys/kern: kern_condvar.c
        src/sys/sys: condvar.h

Log Message:
New cv_timedwaitclock, cv_timedwaitclock_sig.

Usage: given a struct timespec timeout copied from userland, along
with a clockid and TIMER_* flags,

        error = cv_timedwaitclock(cv, lock, timeout, clockid, flags,
            DEFAULT_TIMEOUT_EPSILON);
        if (error)
                /* fail */

If flags is relative (i.e., (flags & TIMER_ABSTIME) == 0), then this
deducts the time spent waiting from timeout, so you can run it in a
loop:

        struct timespec timeout;

        error = copyin(SCARG(uap, timeout), &timeout, sizeof timeout);
        if (error)
                return error;

        mutex_enter(lock);
        while (!ready()) {
                error = cv_timedwaitclock_sig(cv, lock, &timeout,
                    SCARG(uap, clockid), SCARG(uap, flags),
                    DEFAULT_TIMEOUT_EPSILON);
                if (error)
                        break;
        }
        mutex_exit(lock);

CAVEAT: If the system call is interrupted by a signal with SA_RESTART
so cv_timedwaitclock_sig fails with ERESTART, then the system call
will be restarted with the _original_ relative timeout, not counting
the time that was already spent waiting.  This is a problem but it's
not a problem I want to deal with at the moment.


To generate a diff of this commit:
cvs rdiff -u -r1.48 -r1.49 src/sys/kern/kern_condvar.c
cvs rdiff -u -r1.15 -r1.16 src/sys/sys/condvar.h

Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.