On Mon, Jun 27, 2016 at 01:18:48PM -0700, Ngie Cooper wrote:
> On Sun, Jun 26, 2016 at 1:08 PM, Konstantin Belousov <k...@freebsd.org> wrote:
> > Author: kib
> > Date: Sun Jun 26 20:08:42 2016
> > New Revision: 302216
> > URL: https://svnweb.freebsd.org/changeset/base/302216
> >
> > Log:
> > When sleeping waiting for either local or remote advisory lock,
> > interrupt sleeps with the ERESTART on the suspension attempts.
> > Otherwise, single-threading requests are deferred until the locks are
> > granted for NFS files, which causes hangs.
> >
> > When retrying local registration of the remotely-granted adv lock,
> > allow full suspension and check for suspension, for usual reasons.
> >
> > Reported by: markj, pho
> > Reviewed by: jilles
> > Tested by: pho
> > Sponsored by: The FreeBSD Foundation
> > MFC after: 2 weeks
> > Approved by: re (gjb)
>
> One of the NetBSD tests seems to be failing now:
> https://jenkins.freebsd.org/job/FreeBSD_HEAD/334/testReport/junit/sys.kern/lockf_test/randlock/
> .
Indeed. The reason is that TDF_SBDRY + TDF_SERESTART (or TDF_SEINTR)
combination should be treated almost as if TDF_SBDRY is not set, at least
for the purposes of filtering out stops. It must not allow the real stop
to occur at a protected sleep point, though.
The committed revision lacks updates to kern_sig.c to kick the sleeping
thread in TDF_SERESTART condition to make it runnable to reach boundary.
I attached the distilled case from the NetBSD test below. Another good
test case to illustrate that is to do in one terminal
echo 123 >/tmp/1
lockf /tmp/1 sleep 100000
and in another
lockf /tmp/1 date
^Z
This should have failed in similar way on NFS only, before the changes.
The patch attached fixed both cases for me.
diff --git a/sys/kern/kern_sig.c b/sys/kern/kern_sig.c
index 424f316..059103dc 100644
--- a/sys/kern/kern_sig.c
+++ b/sys/kern/kern_sig.c
@@ -107,7 +107,7 @@ static int killpg1(struct thread *td, int sig, int pgid, int all,
static int issignal(struct thread *td);
static int sigprop(int sig);
static void tdsigwakeup(struct thread *, int, sig_t, int);
-static void sig_suspend_threads(struct thread *, struct proc *, int);
+static int sig_suspend_threads(struct thread *, struct proc *, int);
static int filt_sigattach(struct knote *kn);
static void filt_sigdetach(struct knote *kn);
static int filt_signal(struct knote *kn, long hint);
@@ -2327,7 +2327,7 @@ tdsendsignal(struct proc *p, struct thread *td, int sig, ksiginfo_t *ksi)
p->p_flag |= P_STOPPED_SIG;
p->p_xsig = sig;
PROC_SLOCK(p);
- sig_suspend_threads(td, p, 1);
+ wakeup_swapper = sig_suspend_threads(td, p, 1);
if (p->p_numthreads == p->p_suspcount) {
/*
* only thread sending signal to another
@@ -2341,6 +2341,8 @@ tdsendsignal(struct proc *p, struct thread *td, int sig, ksiginfo_t *ksi)
sigqueue_delete_proc(p, p->p_xsig);
} else
PROC_SUNLOCK(p);
+ if (wakeup_swapper)
+ kick_proc0();
goto out;
}
} else {
@@ -2421,7 +2423,8 @@ tdsigwakeup(struct thread *td, int sig, sig_t action, int intrval)
* Don't awaken a sleeping thread for SIGSTOP if the
* STOP signal is deferred.
*/
- if ((prop & SA_STOP) && (td->td_flags & TDF_SBDRY))
+ if ((prop & SA_STOP) != 0 && (td->td_flags & (TDF_SBDRY |
+ TDF_SERESTART | TDF_SEINTR)) == TDF_SBDRY)
goto out;
/*
@@ -2449,14 +2452,16 @@ out:
kick_proc0();
}
-static void
+static int
sig_suspend_threads(struct thread *td, struct proc *p, int sending)
{
struct thread *td2;
+ int wakeup_swapper;
PROC_LOCK_ASSERT(p, MA_OWNED);
PROC_SLOCK_ASSERT(p, MA_OWNED);
+ wakeup_swapper = 0;
FOREACH_THREAD_IN_PROC(p, td2) {
thread_lock(td2);
td2->td_flags |= TDF_ASTPENDING | TDF_NEEDSUSPCHK;
@@ -2465,11 +2470,18 @@ sig_suspend_threads(struct thread *td, struct proc *p, int sending)
if (td2->td_flags & TDF_SBDRY) {
/*
* Once a thread is asleep with
- * TDF_SBDRY set, it should never
+ * TDF_SBDRY and without TDF_SERESTART
+ * or TDF_SEINTR set, it should never
* become suspended due to this check.
*/
KASSERT(!TD_IS_SUSPENDED(td2),
("thread with deferred stops suspended"));
+ if ((td2->td_flags & (TDF_SERESTART |
+ TDF_SEINTR)) != 0 && sending) {
+ wakeup_swapper |= sleepq_abort(td,
+ (td2->td_flags & TDF_SERESTART)
+ != 0 ? ERESTART : EINTR);
+ }
} else if (!TD_IS_SUSPENDED(td2)) {
thread_suspend_one(td2);
}
@@ -2483,6 +2495,7 @@ sig_suspend_threads(struct thread *td, struct proc *p, int sending)
}
thread_unlock(td2);
}
+ return (wakeup_swapper);
}
int
@@ -2705,7 +2718,8 @@ issignal(struct thread *td)
SIGSETOR(sigpending, p->p_sigqueue.sq_signals);
SIGSETNAND(sigpending, td->td_sigmask);
- if (p->p_flag & P_PPWAIT || td->td_flags & TDF_SBDRY)
+ if ((p->p_flag & P_PPWAIT) != 0 || (td->td_flags &
+ (TDF_SBDRY | TDF_SERESTART | TDF_SEINTR)) == TDF_SBDRY)
SIG_STOPSIGMASK(sigpending);
if (SIGISEMPTY(sigpending)) /* no signal to send */
return (0);
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