git: 107bc3da39d3 - stable/13 - filt_timerexpire: avoid process lock recursion

[Konstantin Belousov]

The branch stable/13 has been updated by kib:

URL: 
https://cgit.FreeBSD.org/src/commit/?id=107bc3da39d37bf81b1c9fd3d8b58452d4606404

commit 107bc3da39d37bf81b1c9fd3d8b58452d4606404
Author:     Konstantin Belousov <k...@freebsd.org>
AuthorDate: 2021-04-13 14:25:11 +0000
Commit:     Konstantin Belousov <k...@freebsd.org>
CommitDate: 2021-04-23 11:14:09 +0000

    filt_timerexpire: avoid process lock recursion
    
    (cherry picked from commit 75c5cf7a720f5a73f17aff60adbc4a7b2fa86f84)
---
 sys/kern/kern_event.c | 22 +++++++++++++++-------
 1 file changed, 15 insertions(+), 7 deletions(-)

diff --git a/sys/kern/kern_event.c b/sys/kern/kern_event.c
index 31b091e20984..45d505fca757 100644
--- a/sys/kern/kern_event.c
+++ b/sys/kern/kern_event.c
@@ -161,6 +161,7 @@ static void filt_procdetach(struct knote *kn);
 static int     filt_proc(struct knote *kn, long hint);
 static int     filt_fileattach(struct knote *kn);
 static void    filt_timerexpire(void *knx);
+static void    filt_timerexpire_l(struct knote *kn, bool proc_locked);
 static int     filt_timerattach(struct knote *kn);
 static void    filt_timerdetach(struct knote *kn);
 static void    filt_timerstart(struct knote *kn, sbintime_t to);
@@ -706,21 +707,19 @@ kqtimer_proc_continue(struct proc *p)
        TAILQ_FOREACH_SAFE(kc, &p->p_kqtim_stop, link, kc1) {
                TAILQ_REMOVE(&p->p_kqtim_stop, kc, link);
                if (kc->next <= now)
-                       filt_timerexpire(kc->kn);
+                       filt_timerexpire_l(kc->kn, true);
                else
                        kqtimer_sched_callout(kc);
        }
 }
 
 static void
-filt_timerexpire(void *knx)
+filt_timerexpire_l(struct knote *kn, bool proc_locked)
 {
-       struct knote *kn;
        struct kq_timer_cb_data *kc;
        struct proc *p;
        sbintime_t now;
 
-       kn = knx;
        kc = kn->kn_ptr.p_v;
 
        if ((kn->kn_flags & EV_ONESHOT) != 0 || kc->to == 0) {
@@ -742,17 +741,26 @@ filt_timerexpire(void *knx)
         */
        p = kc->p;
        if (P_SHOULDSTOP(p) || P_KILLED(p)) {
-               PROC_LOCK(p);
+               if (!proc_locked)
+                       PROC_LOCK(p);
                if (P_SHOULDSTOP(p) || P_KILLED(p)) {
                        TAILQ_INSERT_TAIL(&p->p_kqtim_stop, kc, link);
-                       PROC_UNLOCK(p);
+                       if (!proc_locked)
+                               PROC_UNLOCK(p);
                        return;
                }
-               PROC_UNLOCK(p);
+               if (!proc_locked)
+                       PROC_UNLOCK(p);
        }
        kqtimer_sched_callout(kc);
 }
 
+static void
+filt_timerexpire(void *knx)
+{
+       filt_timerexpire_l(knx, false);
+}
+
 /*
  * data contains amount of time to sleep
  */
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