Author: rrs
Date: Tue Jul 19 18:31:19 2016
New Revision: 303037
URL: https://svnweb.freebsd.org/changeset/base/303037
Log:
This reverts out Gleb's changes and adds three small
fixes that I think closes up the races Gleb was
looking for. This is running quite nicely in Netflix and
now no longer causes TCP-tcb leaks.
Differential Revision: 7135
Modified:
head/sys/kern/kern_timeout.c
Modified: head/sys/kern/kern_timeout.c
==============================================================================
--- head/sys/kern/kern_timeout.c Tue Jul 19 18:15:22 2016
(r303036)
+++ head/sys/kern/kern_timeout.c Tue Jul 19 18:31:19 2016
(r303037)
@@ -1050,7 +1050,7 @@ callout_reset_sbt_on(struct callout *c,
*/
if (c->c_lock != NULL && !cc_exec_cancel(cc, direct))
cancelled = cc_exec_cancel(cc, direct) = true;
- if (cc_exec_waiting(cc, direct)) {
+ if (cc_exec_waiting(cc, direct) || cc_exec_drain(cc, direct)) {
/*
* Someone has called callout_drain to kill this
* callout. Don't reschedule.
@@ -1166,7 +1166,7 @@ _callout_stop_safe(struct callout *c, in
struct callout_cpu *cc, *old_cc;
struct lock_class *class;
int direct, sq_locked, use_lock;
- int cancelled, not_on_a_list;
+ int not_on_a_list;
if ((flags & CS_DRAIN) != 0)
WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, c->c_lock,
@@ -1234,17 +1234,47 @@ again:
panic("migration should not happen");
#endif
}
-
+ if ((drain != NULL) && (c->c_iflags & CALLOUT_PENDING) &&
+ (cc_exec_curr(cc, direct) != c)) {
+ /*
+ * This callout is executing and we are draining.
+ * The only way this can happen is if its also
+ * been rescheduled to run on one thread *and* asked to drain
+ * on this thread (at the same time it is waiting to execute).
+ */
+ if ((c->c_iflags & CALLOUT_PROCESSED) == 0) {
+ if (cc_exec_next(cc) == c)
+ cc_exec_next(cc) = LIST_NEXT(c, c_links.le);
+ LIST_REMOVE(c, c_links.le);
+ } else {
+ TAILQ_REMOVE(&cc->cc_expireq, c, c_links.tqe);
+ }
+ c->c_iflags &= ~CALLOUT_PENDING;
+ c->c_flags &= ~CALLOUT_ACTIVE;
+ }
/*
- * If the callout is running, try to stop it or drain it.
+ * If the callout isn't pending, it's not on the queue, so
+ * don't attempt to remove it from the queue. We can try to
+ * stop it by other means however.
*/
- if (cc_exec_curr(cc, direct) == c) {
+ if (!(c->c_iflags & CALLOUT_PENDING)) {
/*
- * Succeed we to stop it or not, we must clear the
- * active flag - this is what API users expect.
+ * If it wasn't on the queue and it isn't the current
+ * callout, then we can't stop it, so just bail.
+ * It probably has already been run (if locking
+ * is properly done). You could get here if the caller
+ * calls stop twice in a row for example. The second
+ * call would fall here without CALLOUT_ACTIVE set.
*/
c->c_flags &= ~CALLOUT_ACTIVE;
-
+ if (cc_exec_curr(cc, direct) != c) {
+ CTR3(KTR_CALLOUT, "failed to stop %p func %p arg %p",
+ c, c->c_func, c->c_arg);
+ CC_UNLOCK(cc);
+ if (sq_locked)
+ sleepq_release(&cc_exec_waiting(cc, direct));
+ return (-1);
+ }
if ((flags & CS_DRAIN) != 0) {
/*
* The current callout is running (or just
@@ -1278,7 +1308,6 @@ again:
old_cc = cc;
goto again;
}
-
/*
* Migration could be cancelled here, but
* as long as it is still not sure when it
@@ -1362,6 +1391,8 @@ again:
cc_exec_drain(cc, direct) = drain;
}
CC_UNLOCK(cc);
+ if (drain)
+ return(0);
return ((flags & CS_EXECUTING) != 0);
}
CTR3(KTR_CALLOUT, "failed to stop %p func %p arg %p",
@@ -1369,20 +1400,12 @@ again:
if (drain) {
cc_exec_drain(cc, direct) = drain;
}
- KASSERT(!sq_locked, ("sleepqueue chain still locked"));
- cancelled = ((flags & CS_EXECUTING) != 0);
- } else
- cancelled = 1;
-
- if (sq_locked)
- sleepq_release(&cc_exec_waiting(cc, direct));
-
- if ((c->c_iflags & CALLOUT_PENDING) == 0) {
- CTR3(KTR_CALLOUT, "failed to stop %p func %p arg %p",
- c, c->c_func, c->c_arg);
CC_UNLOCK(cc);
+ KASSERT(!sq_locked, ("sleepqueue chain still locked"));
return (0);
}
+ if (sq_locked)
+ sleepq_release(&cc_exec_waiting(cc, direct));
c->c_iflags &= ~CALLOUT_PENDING;
c->c_flags &= ~CALLOUT_ACTIVE;
@@ -1400,7 +1423,7 @@ again:
}
callout_cc_del(c, cc);
CC_UNLOCK(cc);
- return (cancelled);
+ return (1);
}
void
@@ -1615,7 +1638,6 @@ SYSCTL_PROC(_kern, OID_AUTO, callout_sta
CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_MPSAFE,
0, 0, sysctl_kern_callout_stat, "I",
"Dump immediate statistic snapshot of the scheduled callouts");
-
#ifdef DDB
static void
_show_callout(struct callout *c)
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