further select refinements (from torek via karels)

SCCS-vsn: sys/kern/sys_generic.c 8.8

diff --git a/usr/src/sys/kern/sys_generic.c b/usr/src/sys/kern/sys_generic.c
index be609f2..403f824 100644 (file)
--- a/usr/src/sys/kern/sys_generic.c
+++ b/usr/src/sys/kern/sys_generic.c
@@ -9,7 +9,7 @@
  *
  * %sccs.include.redist.c%
  *
  *
  * %sccs.include.redist.c%
  *

- *     @(#)sys_generic.c       8.7 (Berkeley) %G%
+ *     @(#)sys_generic.c       8.8 (Berkeley) %G%

  */
 
 #include <sys/param.h>
  */
 
 #include <sys/param.h>


@@ -463,6 +463,7 @@ struct select_args {
        fd_set  *in, *ou, *ex;
        struct  timeval *tv;
 };
        fd_set  *in, *ou, *ex;
        struct  timeval *tv;
 };

+

 select(p, uap, retval)
        register struct proc *p;
        register struct select_args *uap;
 select(p, uap, retval)
        register struct proc *p;
        register struct select_args *uap;


@@ -470,7 +471,7 @@ select(p, uap, retval)
 {
        fd_set ibits[3], obits[3];
        struct timeval atv;
 {
        fd_set ibits[3], obits[3];
        struct timeval atv;

-       int s, ncoll, error = 0, timo, doblock;
+       int s, ncoll, error, timo = 0;

        u_int ni;
 
        bzero((caddr_t)ibits, sizeof(ibits));
        u_int ni;
 
        bzero((caddr_t)ibits, sizeof(ibits));


@@ -499,17 +500,10 @@ select(p, uap, retval)
                        error = EINVAL;
                        goto done;
                }
                        error = EINVAL;
                        goto done;
                }

-               /*
-                * Don't let a short time get rounded down to zero
-                * and cause us to sleep forever, but exactly zero
-                * means "do not block".
-                */
-               doblock = (atv.tv_usec || atv.tv_sec);

                s = splclock();
                timevaladd(&atv, (struct timeval *)&time);
                splx(s);
                s = splclock();
                timevaladd(&atv, (struct timeval *)&time);
                splx(s);

-       } else
-               timo = 0;
+       }

 retry:
        ncoll = nselcoll;
        p->p_flag |= P_SELECT;
 retry:
        ncoll = nselcoll;
        p->p_flag |= P_SELECT;


@@ -522,11 +516,15 @@ retry:
                        splx(s);
                        goto done;
                }
                        splx(s);
                        goto done;
                }

-               timo = hzto(&atv);

                /*
                /*

-                * Avoid inadvertently sleeping forever.
+                * If poll wait was tiny, this could be zero; we will
+                * have to round it up to avoid sleeping forever.  If
+                * we retry below, the timercmp above will get us out.
+                * Note that if wait was 0, the timercmp will prevent
+                * us from getting here the first time.

                 */
                 */

-               if (doblock && timo == 0)
+               timo = hzto(&atv);
+               if (timo == 0)

                        timo = 1;
        }
        if ((p->p_flag & P_SELECT) == 0 || nselcoll != ncoll) {
                        timo = 1;
        }
        if ((p->p_flag & P_SELECT) == 0 || nselcoll != ncoll) {


@@ -534,7 +532,6 @@ retry:
                goto retry;
        }
        p->p_flag &= ~P_SELECT;
                goto retry;
        }
        p->p_flag &= ~P_SELECT;

-       doblock = 0;

        error = tsleep((caddr_t)&selwait, PSOCK | PCATCH, "select", timo);
        splx(s);
        if (error == 0)
        error = tsleep((caddr_t)&selwait, PSOCK | PCATCH, "select", timo);
        splx(s);
        if (error == 0)