svn commit: r236744 - in projects/calloutng/sys: kern sys

[Davide Italiano]

On Fri, Jun 8, 2012 at 2:52 PM, Attilio Rao <attilio at freebsd.org> wrote:
> 2012/6/8 Davide Italiano <davide at freebsd.org>:
>> Author: davide
>> Date: Fri Jun  8 11:53:51 2012
>> New Revision: 236744
>> URL: http://svn.freebsd.org/changeset/base/236744
>>
>> Log:
>>  Add (experimentally) a function to the sleepqueue(9) KPI
>>  sleepq_set_timeout_bt() in which the timeout may be specified in terms
>>  of bintime rather than ticks, and which takes advantage of the new
>>  precision capabilities of the callout subsystem.
>>
>>  Modify the kern_nanosleep() function so that it may rely on
>>  sleepq_set_timeout_bt() rather than tsleep().
>>
>> Modified:
>>  projects/calloutng/sys/kern/kern_time.c
>>  projects/calloutng/sys/kern/subr_sleepqueue.c
>>  projects/calloutng/sys/sys/sleepqueue.h
>>
>> Modified: projects/calloutng/sys/kern/kern_time.c
>> ==============================================================================
>> --- projects/calloutng/sys/kern/kern_time.c     Fri Jun  8 11:40:30 2012        (r236743)
>> +++ projects/calloutng/sys/kern/kern_time.c     Fri Jun  8 11:53:51 2012        (r236744)
>> @@ -43,6 +43,7 @@ __FBSDID("$FreeBSD$");
>>  #include <sys/resourcevar.h>
>>  #include <sys/signalvar.h>
>>  #include <sys/kernel.h>
>> +#include <sys/sleepqueue.h>
>>  #include <sys/syscallsubr.h>
>>  #include <sys/sysctl.h>
>>  #include <sys/sysent.h>
>> @@ -352,37 +353,40 @@ static int nanowait;
>>  int
>>  kern_nanosleep(struct thread *td, struct timespec *rqt, struct timespec *rmt)
>>  {
>> -       struct timespec ts, ts2, ts3;
>> -       struct timeval tv;
>> -       int error;
>> +       struct timespec ts;
>> +       struct bintime bt, bt2, tmp;
>> +       int catch = 0, error;
>>
>>        if (rqt->tv_nsec < 0 || rqt->tv_nsec >= 1000000000)
>>                return (EINVAL);
>>        if (rqt->tv_sec < 0 || (rqt->tv_sec == 0 && rqt->tv_nsec == 0))
>>                return (0);
>> -       getnanouptime(&ts);
>> -       timespecadd(&ts, rqt);
>> -       TIMESPEC_TO_TIMEVAL(&tv, rqt);
>> +       binuptime(&bt);
>> +       timespec2bintime(rqt, &tmp);
>> +       bintime_add(&bt,&tmp);
>>        for (;;) {
>> -               error = tsleep(&nanowait, PWAIT | PCATCH, "nanslp",
>> -                   tvtohz(&tv));
>> -               getnanouptime(&ts2);
>> -               if (error != EWOULDBLOCK) {
>> -                       if (error == ERESTART)
>> -                               error = EINTR;
>> -                       if (rmt != NULL) {
>> -                               timespecsub(&ts, &ts2);
>> -                               if (ts.tv_sec < 0)
>> -                                       timespecclear(&ts);
>> -                               *rmt = ts;
>> -                       }
>> +               sleepq_lock(&nanowait);
>> +               sleepq_add(&nanowait, NULL, "nanslp", PWAIT | PCATCH, 0);
>> +               sleepq_set_timeout_bt(&nanowait,bt);
>> +               error = sleepq_timedwait_sig(&nanowait,catch);
>> +               binuptime(&bt2);
>> +               if (catch) {
>> +                       if (error != EWOULDBLOCK) {
>> +                               if (error == ERESTART)
>> +                                       error = EINTR;
>> +                               if (rmt != NULL) {
>> +                                       tmp = bt;
>> +                                       bintime_sub(&tmp, &bt2);
>> +                                       bintime2timespec(&tmp,&ts);
>> +                                       if (ts.tv_sec < 0)
>> +                                               timespecclear(&ts);
>> +                                       *rmt = ts;
>> +                               }
>>                        return (error);
>> +                       }
>>                }
>> -               if (timespeccmp(&ts2, &ts, >=))
>> +               if (bintime_cmp(&bt2, &bt, >=))
>>                        return (0);
>> -               ts3 = ts;
>> -               timespecsub(&ts3, &ts2);
>> -               TIMESPEC_TO_TIMEVAL(&tv, &ts3);
>>        }
>>  }
>>
>>
>> Modified: projects/calloutng/sys/kern/subr_sleepqueue.c
>> ==============================================================================
>> --- projects/calloutng/sys/kern/subr_sleepqueue.c       Fri Jun  8 11:40:30 2012        (r236743)
>> +++ projects/calloutng/sys/kern/subr_sleepqueue.c       Fri Jun  8 11:53:51 2012        (r236744)
>> @@ -361,6 +361,22 @@ sleepq_add(void *wchan, struct lock_obje
>>  * Sets a timeout that will remove the current thread from the specified
>>  * sleep queue after timo ticks if the thread has not already been awakened.
>>  */
>> +void
>> +sleepq_set_timeout_bt(void *wchan, struct bintime bt)
>> +{
>> +
>> +       struct sleepqueue_chain *sc;
>> +       struct thread *td;
>> +
>> +       td = curthread;
>> +       sc = SC_LOOKUP(wchan);
>> +       mtx_assert(&sc->sc_lock, MA_OWNED);
>> +       MPASS(TD_ON_SLEEPQ(td));
>> +       MPASS(td->td_sleepqueue == NULL);
>> +       MPASS(wchan != NULL);
>> +       callout_reset_bt_on(&td->td_slpcallout, bt, sleepq_timeout, td, PCPU_GET(cpuid));
>> +}
>> +
>
> For this, I'd rather prefer that you patch sleepq_set_timeout() directly to be:
> void sleepq_set_timeout(void *wchan, int timo, struct bintime *bt);u
>
> Then, if you pass a NULL ptr to bt the 'timo' is used, otherwise bt is
> given preference in the logic. You will need to patch the current few
> callers of sleepq_set_timo() to get NULL, but it is a small patch.
> I would really like that you do the same also in the callout KPI,
> possibly, because this avoids a lot of code duplication.
>
> Attilio
>
>
> --
> Peace can only be achieved by understanding - A. Einstein

Attilio,
I agree with you about the few clients of sleepq_set_timeout(), and I
may change it easily.
About the callout_* KPI, if you refer to the recently added
callout_reset_bt_on() function, I have some concerns.
Right now, the number of consumers of callout_reset() or
callout_reset_on() is a lot bigger than the one of
sleepq_set_timeout() to consider a change, at least from my point of
view.
Moreover, differently from previous case, callout_reset_bt_on()
doesn't duplicate code because I've moved the old code there and made
callout_reset_on() a wrapper in which conversion is made and
callout_reset_bt_on() is called.

Davide