minor bugfix (avoid unlikely race)

[unix-history] / usr / src / lib / libc / gen / sleep.c

#ifndef lint
static char sccsid[] = "@(#)sleep.c     4.6 (Berkeley) %G%";
#endif

#include <sys/time.h>
#include <signal.h>

#define mask(s) (1<<((s)-1))
#define setvec(vec, a) \
       vec.sv_handler = a; vec.sv_mask = vec.sv_onstack = 0

static int ringring;

sleep(n)
       unsigned n;
{
       int sleepx(), omask;
       struct itimerval itv, oitv;
       register struct itimerval *itp = &itv;
       struct sigvec vec, ovec;

       if (n == 0)
               return;
       timerclear(&itp->it_interval);
       timerclear(&itp->it_value);
       if (setitimer(ITIMER_REAL, itp, &oitv) < 0)
               return;
       setvec(ovec, SIG_DFL);
       omask = sigblock(0);
       itp->it_value.tv_sec = n;
       if (timerisset(&oitv.it_value)) {
               if (timercmp(&oitv.it_value, &itp->it_value, >))
                       oitv.it_value.tv_sec -= itp->it_value.tv_sec;
               else {
                       itp->it_value = oitv.it_value;
                       /*
                        * This is a hack, but we must have time to
                        * return from the setitimer after the alarm
                        * or else it'll be restarted.  And, anyway,
                        * sleep never did anything more than this before.
                        */
                       oitv.it_value.tv_sec = 1;
                       oitv.it_value.tv_usec = 0;
               }
       }
       setvec(vec, sleepx);
       (void) sigvec(SIGALRM, &vec, &ovec);
       ringring = 0;
       (void) setitimer(ITIMER_REAL, itp, (struct itimerval *)0);
       while (!ringring)
               sigpause(omask &~ mask(SIGALRM));
       (void) sigvec(SIGALRM, &ovec, (struct sigvec *)0);
       (void) setitimer(ITIMER_REAL, &oitv, (struct itimerval *)0);
}

static
sleepx()
{

       ringring = 1;
}