Author: jamie
Date: Wed Apr 27 02:25:21 2016
New Revision: 298683
URL: https://svnweb.freebsd.org/changeset/base/298683
Log:
Delay revmoing the last jail reference in prison_proc_free, and instead
put it off into the pr_task. This is similar to prison_free, and in fact
uses the same task even though they do something slightly different.
This resolves a LOR between the process lock and allprison_lock, which
came about in r298565.
PR: 48471
Modified:
head/sys/kern/kern_jail.c
head/sys/sys/jail.h
Modified: head/sys/kern/kern_jail.c
==============================================================================
--- head/sys/kern/kern_jail.c Wed Apr 27 02:13:57 2016 (r298682)
+++ head/sys/kern/kern_jail.c Wed Apr 27 02:25:21 2016 (r298683)
@@ -1328,6 +1328,7 @@ kern_jail_set(struct thread *td, struct
LIST_INIT(&pr->pr_children);
mtx_init(&pr->pr_mtx, "jail mutex", NULL, MTX_DEF | MTX_DUPOK);
+ TASK_INIT(&pr->pr_task, 0, prison_complete, pr);
#ifdef VIMAGE
/* Allocate a new vnet if specified. */
@@ -2575,16 +2576,13 @@ prison_allow(struct ucred *cred, unsigne
void
prison_free_locked(struct prison *pr)
{
+ int ref;
mtx_assert(&pr->pr_mtx, MA_OWNED);
- pr->pr_ref--;
- if (pr->pr_ref == 0) {
- mtx_unlock(&pr->pr_mtx);
- TASK_INIT(&pr->pr_task, 0, prison_complete, pr);
- taskqueue_enqueue(taskqueue_thread, &pr->pr_task);
- return;
- }
+ ref = --pr->pr_ref;
mtx_unlock(&pr->pr_mtx);
+ if (ref == 0)
+ taskqueue_enqueue(taskqueue_thread, &pr->pr_task);
}
void
@@ -2595,11 +2593,17 @@ prison_free(struct prison *pr)
prison_free_locked(pr);
}
+/*
+ * Complete a call to either prison_free or prison_proc_free.
+ */
static void
prison_complete(void *context, int pending)
{
+ struct prison *pr = context;
- prison_deref((struct prison *)context, 0);
+ mtx_lock(&pr->pr_mtx);
+ prison_deref(pr, pr->pr_uref
+ ? PD_DEREF | PD_DEUREF | PD_LOCKED : PD_LOCKED);
}
/*
@@ -2618,6 +2622,9 @@ prison_deref(struct prison *pr, int flag
mtx_lock(&pr->pr_mtx);
for (;;) {
if (flags & PD_DEUREF) {
+ KASSERT(pr->pr_uref > 0,
+ ("prison_deref PD_DEUREF on a dead prison (jid=%d)",
+ pr->pr_id));
pr->pr_uref--;
lasturef = pr->pr_uref == 0;
if (lasturef)
@@ -2625,8 +2632,12 @@ prison_deref(struct prison *pr, int flag
KASSERT(prison0.pr_uref != 0, ("prison0 pr_uref=0"));
} else
lasturef = 0;
- if (flags & PD_DEREF)
+ if (flags & PD_DEREF) {
+ KASSERT(pr->pr_ref > 0,
+ ("prison_deref PD_DEREF on a dead prison (jid=%d)",
+ pr->pr_id));
pr->pr_ref--;
+ }
ref = pr->pr_ref;
mtx_unlock(&pr->pr_mtx);
@@ -2740,7 +2751,20 @@ prison_proc_free(struct prison *pr)
mtx_lock(&pr->pr_mtx);
KASSERT(pr->pr_uref > 0,
("Trying to kill a process in a dead prison (jid=%d)", pr->pr_id));
- prison_deref(pr, PD_DEUREF | PD_LOCKED);
+ if (pr->pr_uref > 1)
+ pr->pr_uref--;
+ else {
+ /*
+ * Don't remove the last user reference in this context, which
+ * is expected to be a process that is not only locked, but
+ * also half dead.
+ */
+ pr->pr_ref++;
+ mtx_unlock(&pr->pr_mtx);
+ taskqueue_enqueue(taskqueue_thread, &pr->pr_task);
+ return;
+ }
+ mtx_unlock(&pr->pr_mtx);
}
Modified: head/sys/sys/jail.h
==============================================================================
--- head/sys/sys/jail.h Wed Apr 27 02:13:57 2016 (r298682)
+++ head/sys/sys/jail.h Wed Apr 27 02:25:21 2016 (r298683)
@@ -149,7 +149,6 @@ struct prison_racct;
* (p) locked by pr_mtx
* (c) set only during creation before the structure is shared, no mutex
* required to read
- * (d) set only during destruction of jail, no mutex needed
*/
struct prison {
TAILQ_ENTRY(prison) pr_list; /* (a) all prisons */
@@ -161,7 +160,7 @@ struct prison {
LIST_ENTRY(prison) pr_sibling; /* (a) next in parent's
list */
struct prison *pr_parent; /* (c) containing jail
*/
struct mtx pr_mtx;
- struct task pr_task; /* (d) destroy task */
+ struct task pr_task; /* (c) destroy task */
struct osd pr_osd; /* (p) additional data
*/
struct cpuset *pr_cpuset; /* (p) cpuset */
struct vnet *pr_vnet; /* (c) network stack */
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