jail: Clean up some function placement and improve comments.
Move prison_hold, prison_hold_locked ,prison_proc_hold, and prison_proc_free to a more intuitive part of the file (together with with prison_free and prison_free_locked), and add or improve comments to these and others, to better describe what's going in the prison reference cycle. No functional changes.
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@ -2604,8 +2604,35 @@ prison_allow(struct ucred *cred, unsigned flag)
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}
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/*
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* Remove a prison reference. If that was the last reference, remove the
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* prison itself - but not in this context in case there are locks held.
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* Hold a prison reference, by incrementing pr_ref. It is generally
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* an error to hold a prison that does not already have a reference.
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* A prison record will remain valid as long as it has at least one
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* reference, and will not be removed as long as either the prison
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* mutex or the allprison lock is held (allprison_lock may be shared).
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*/
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void
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prison_hold_locked(struct prison *pr)
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{
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mtx_assert(&pr->pr_mtx, MA_OWNED);
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KASSERT(pr->pr_ref > 0,
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("Trying to hold dead prison %p (jid=%d).", pr, pr->pr_id));
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pr->pr_ref++;
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}
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void
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prison_hold(struct prison *pr)
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{
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mtx_lock(&pr->pr_mtx);
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prison_hold_locked(pr);
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mtx_unlock(&pr->pr_mtx);
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}
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/*
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* Remove a prison reference. If that was the last reference, the
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* prison will be removed (at a later time). Return with the prison
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* unlocked.
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*/
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void
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prison_free_locked(struct prison *pr)
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@ -2615,9 +2642,14 @@ prison_free_locked(struct prison *pr)
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mtx_assert(&pr->pr_mtx, MA_OWNED);
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ref = --pr->pr_ref;
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mtx_unlock(&pr->pr_mtx);
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if (ref == 0)
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if (ref == 0) {
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/*
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* Don't remove the last reference in this context,
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* in case there are locks held.
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*/
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taskqueue_enqueue(taskqueue_thread, &pr->pr_task);
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}
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}
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void
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prison_free(struct prison *pr)
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@ -2627,6 +2659,54 @@ prison_free(struct prison *pr)
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prison_free_locked(pr);
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}
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/*
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* Hold a a prison for user visibility, by incrementing pr_uref.
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* It is generally an error to hold a prison that isn't already
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* user-visible, except through the the jail system calls. It is also
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* an error to hold an invalid prison. A prison record will remain
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* alive as long as it has at least one user reference, and will not
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* be set to the dying state was long as the prison mutex is held.
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*/
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void
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prison_proc_hold(struct prison *pr)
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{
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mtx_lock(&pr->pr_mtx);
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KASSERT(pr->pr_uref > 0,
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("Cannot add a process to a non-alive prison (jid=%d)", pr->pr_id));
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pr->pr_uref++;
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mtx_unlock(&pr->pr_mtx);
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}
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/*
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* Remove a prison user reference. If it was the last reference, the
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* prison will be considered "dying", and may be removed once all of
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* its references are dropped.
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*/
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void
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prison_proc_free(struct prison *pr)
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{
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mtx_lock(&pr->pr_mtx);
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KASSERT(pr->pr_uref > 0,
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("Trying to kill a process in a dead prison (jid=%d)", pr->pr_id));
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if (pr->pr_uref > 1)
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pr->pr_uref--;
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else {
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/*
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* Don't remove the last user reference in this context,
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* which is expected to be a process that is not only locked,
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* but also half dead. Add a reference so any calls to
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* prison_free() won't re-submit the task.
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*/
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pr->pr_ref++;
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mtx_unlock(&pr->pr_mtx);
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taskqueue_enqueue(taskqueue_thread, &pr->pr_task);
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return;
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}
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mtx_unlock(&pr->pr_mtx);
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}
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/*
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* Complete a call to either prison_free or prison_proc_free.
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*/
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@ -2637,16 +2717,24 @@ prison_complete(void *context, int pending)
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sx_xlock(&allprison_lock);
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mtx_lock(&pr->pr_mtx);
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prison_deref(pr, pr->pr_uref
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/*
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* If this is completing a call to prison_proc_free, there will still
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* be a user reference held; clear that as well as the reference that
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* was added. No references are expected if this is completing a call
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* to prison_free, but prison_deref is still called for the cleanup.
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*/
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prison_deref(pr, pr->pr_uref > 0
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? PD_DEREF | PD_DEUREF | PD_LOCKED | PD_LIST_XLOCKED
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: PD_LOCKED | PD_LIST_XLOCKED);
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}
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/*
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* Remove a prison reference (usually). This internal version assumes no
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* mutexes are held, except perhaps the prison itself. If there are no more
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* references, release and delist the prison. On completion, the prison lock
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* and the allprison lock are both unlocked.
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* Remove a prison reference and/or user reference (usually).
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* This assumes context that allows sleeping (for allprison_lock),
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* with no non-sleeping locks held, except perhaps the prison itself.
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* If there are no more references, release and delist the prison.
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* On completion, the prison lock and the allprison lock are both
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* unlocked.
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*/
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static void
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prison_deref(struct prison *pr, int flags)
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@ -2750,59 +2838,6 @@ prison_deref(struct prison *pr, int flags)
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}
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}
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void
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prison_hold_locked(struct prison *pr)
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{
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mtx_assert(&pr->pr_mtx, MA_OWNED);
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KASSERT(pr->pr_ref > 0,
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("Trying to hold dead prison %p (jid=%d).", pr, pr->pr_id));
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pr->pr_ref++;
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}
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void
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prison_hold(struct prison *pr)
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{
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mtx_lock(&pr->pr_mtx);
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prison_hold_locked(pr);
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mtx_unlock(&pr->pr_mtx);
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}
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void
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prison_proc_hold(struct prison *pr)
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{
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mtx_lock(&pr->pr_mtx);
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KASSERT(pr->pr_uref > 0,
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("Cannot add a process to a non-alive prison (jid=%d)", pr->pr_id));
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pr->pr_uref++;
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mtx_unlock(&pr->pr_mtx);
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}
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void
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prison_proc_free(struct prison *pr)
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{
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mtx_lock(&pr->pr_mtx);
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KASSERT(pr->pr_uref > 0,
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("Trying to kill a process in a dead prison (jid=%d)", pr->pr_id));
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if (pr->pr_uref > 1)
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pr->pr_uref--;
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else {
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/*
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* Don't remove the last user reference in this context, which
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* is expected to be a process that is not only locked, but
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* also half dead.
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*/
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pr->pr_ref++;
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mtx_unlock(&pr->pr_mtx);
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taskqueue_enqueue(taskqueue_thread, &pr->pr_task);
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return;
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}
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mtx_unlock(&pr->pr_mtx);
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}
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/*
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* Set or clear a permission bit in the pr_allow field, passing restrictions
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* (cleared permission) down to child jails.
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