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[src/trunk]: src/sys/kern Oops. If a SCHED_RR thread is preempted and has ex...



details:   https://anonhg.NetBSD.org/src/rev/260c75d078d0
branches:  trunk
changeset: 1010360:260c75d078d0
user:      ad <ad%NetBSD.org@localhost>
date:      Sat May 23 21:24:41 2020 +0000

description:
Oops.  If a SCHED_RR thread is preempted and has exceeded its timeslice it
needs to go to the back of the run queue so round-robin actually happens,
otherwise it should go to the front.

diffstat:

 sys/kern/kern_runq.c  |  32 +++++++++++++++++++++++++++-----
 sys/kern/sched_4bsd.c |  14 +++++++-------
 sys/kern/sched_m2.c   |  12 ++++++------
 3 files changed, 40 insertions(+), 18 deletions(-)

diffs (168 lines):

diff -r 699637bcab4c -r 260c75d078d0 sys/kern/kern_runq.c
--- a/sys/kern/kern_runq.c      Sat May 23 21:14:55 2020 +0000
+++ b/sys/kern/kern_runq.c      Sat May 23 21:24:41 2020 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: kern_runq.c,v 1.68 2020/05/23 21:14:55 ad Exp $        */
+/*     $NetBSD: kern_runq.c,v 1.69 2020/05/23 21:24:41 ad Exp $        */
 
 /*-
  * Copyright (c) 2019, 2020 The NetBSD Foundation, Inc.
@@ -56,7 +56,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: kern_runq.c,v 1.68 2020/05/23 21:14:55 ad Exp $");
+__KERNEL_RCSID(0, "$NetBSD: kern_runq.c,v 1.69 2020/05/23 21:24:41 ad Exp $");
 
 #include "opt_dtrace.h"
 
@@ -206,9 +206,31 @@
                KASSERT((spc->spc_bitmap[i] & q) == 0);
                spc->spc_bitmap[i] |= q;
        }
-       /* Preempted SCHED_RR and SCHED_FIFO LWPs go to the queue head. */
-       if (l->l_class != SCHED_OTHER && (l->l_pflag & LP_PREEMPTING) != 0) {
-               TAILQ_INSERT_HEAD(q_head, l, l_runq);
+
+       /*
+        * Determine run queue position according to POSIX.  XXX Explicitly
+        * lowering a thread's priority with pthread_setschedparam() is not
+        * handled.
+        */
+       if ((l->l_pflag & LP_PREEMPTING) != 0) {
+               switch (l->l_class) {
+               case SCHED_OTHER:
+                       TAILQ_INSERT_TAIL(q_head, l, l_runq);
+                       break;
+               case SCHED_FIFO:
+                       TAILQ_INSERT_HEAD(q_head, l, l_runq);
+                       break;
+               case SCHED_RR:
+                       if (getticks() - l->l_rticks >= sched_rrticks) {
+                               TAILQ_INSERT_TAIL(q_head, l, l_runq);
+                       } else {
+                               TAILQ_INSERT_HEAD(q_head, l, l_runq);
+                       }
+                       break;
+               default: /* SCHED_OTHER */
+                       panic("sched_enqueue: LWP %p has class %d\n",
+                           l, l->l_class);
+               }
        } else {
                TAILQ_INSERT_TAIL(q_head, l, l_runq);
        }
diff -r 699637bcab4c -r 260c75d078d0 sys/kern/sched_4bsd.c
--- a/sys/kern/sched_4bsd.c     Sat May 23 21:14:55 2020 +0000
+++ b/sys/kern/sched_4bsd.c     Sat May 23 21:24:41 2020 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: sched_4bsd.c,v 1.43 2020/03/12 10:44:00 ad Exp $       */
+/*     $NetBSD: sched_4bsd.c,v 1.44 2020/05/23 21:24:41 ad Exp $       */
 
 /*
  * Copyright (c) 1999, 2000, 2004, 2006, 2007, 2008, 2019, 2020
@@ -69,7 +69,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: sched_4bsd.c,v 1.43 2020/03/12 10:44:00 ad Exp $");
+__KERNEL_RCSID(0, "$NetBSD: sched_4bsd.c,v 1.44 2020/05/23 21:24:41 ad Exp $");
 
 #include "opt_ddb.h"
 #include "opt_lockdebug.h"
@@ -93,11 +93,11 @@
 extern unsigned int sched_pstats_ticks; /* defined in kern_synch.c */
 
 /* Number of hardclock ticks per sched_tick() */
-static int rrticks __read_mostly;
+u_int sched_rrticks __read_mostly;
 
 /*
  * Force switch among equal priority processes every 100ms.
- * Called from hardclock every hz/10 == rrticks hardclock ticks.
+ * Called from hardclock every hz/10 == sched_rrticks hardclock ticks.
  */
 /* ARGSUSED */
 void
@@ -107,7 +107,7 @@
        pri_t pri = PRI_NONE;
        lwp_t *l;
 
-       spc->spc_ticks = rrticks;
+       spc->spc_ticks = sched_rrticks;
 
        if (CURCPU_IDLE_P()) {
                spc_lock(ci);
@@ -534,7 +534,7 @@
 sysctl_sched_rtts(SYSCTLFN_ARGS)
 {
        struct sysctlnode node;
-       int rttsms = hztoms(rrticks);
+       int rttsms = hztoms(sched_rrticks);
 
        node = *rnode;
        node.sysctl_data = &rttsms;
@@ -555,7 +555,7 @@
        if (node == NULL)
                return;
 
-       rrticks = hz / 10;
+       sched_rrticks = hz / 10;
 
        sysctl_createv(NULL, 0, &node, NULL,
                CTLFLAG_PERMANENT,
diff -r 699637bcab4c -r 260c75d078d0 sys/kern/sched_m2.c
--- a/sys/kern/sched_m2.c       Sat May 23 21:14:55 2020 +0000
+++ b/sys/kern/sched_m2.c       Sat May 23 21:24:41 2020 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: sched_m2.c,v 1.38 2020/04/13 15:54:45 maxv Exp $       */
+/*     $NetBSD: sched_m2.c,v 1.39 2020/05/23 21:24:41 ad Exp $ */
 
 /*
  * Copyright (c) 2007, 2008 Mindaugas Rasiukevicius <rmind at NetBSD org>
@@ -33,7 +33,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: sched_m2.c,v 1.38 2020/04/13 15:54:45 maxv Exp $");
+__KERNEL_RCSID(0, "$NetBSD: sched_m2.c,v 1.39 2020/05/23 21:24:41 ad Exp $");
 
 #include <sys/param.h>
 
@@ -68,9 +68,9 @@
  */
 static u_int   min_ts;                 /* Minimal time-slice */
 static u_int   max_ts;                 /* Maximal time-slice */
-static u_int   rt_ts;                  /* Real-time time-slice */
 static u_int   ts_map[PRI_COUNT];      /* Map of time-slices */
 static pri_t   high_pri[PRI_COUNT];    /* Map for priority increase */
+u_int          sched_rrticks;          /* Real-time time-slice */
 
 static void    sched_precalcts(void);
 
@@ -88,7 +88,7 @@
        /* Default timing ranges */
        min_ts = mstohz(20);                    /*  ~20 ms */
        max_ts = mstohz(150);                   /* ~150 ms */
-       rt_ts = mstohz(100);                    /* ~100 ms */
+       sched_rrticks = mstohz(100);                    /* ~100 ms */
        sched_precalcts();
 
 #ifdef notdef
@@ -117,7 +117,7 @@
 
        /* Real-time range */
        for (p = (PRI_HIGHEST_TS + 1); p < PRI_COUNT; p++) {
-               ts_map[p] = rt_ts;
+               ts_map[p] = sched_rrticks;
                high_pri[p] = p;
        }
 }
@@ -346,7 +346,7 @@
 sysctl_sched_rtts(SYSCTLFN_ARGS)
 {
        struct sysctlnode node;
-       int rttsms = hztoms(rt_ts);
+       int rttsms = hztoms(sched_rrticks);
 
        node = *rnode;
        node.sysctl_data = &rttsms;



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