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- Move the 'clk' spinlock below other spin locks since KTR trace events
may need the clock lock for nanotime(). - Add KTR trace events for lock list manipulations and other witness operations. - Use a temporary variable instead of setting the lock list head directly and then setting up the links to add a new lock list entry to the lock list. This small race could result in witness "forgetting" about all the locks held by this process temporarily during an interrupt. - Close a more fatal race condition when removing a lock from a list. Removing a lock from the list entails both decrementing the count of items in this bucket as well as shuffling items in the current bucket up a notch to replace the gap left by the removed item. Wrap these operations in a critical section.
This commit is contained in:
John Baldwin
parent
1715f07da3
commit
b7e554f5d6
Notes:
svn2git
2020-12-20 02:59:44 +00:00
svn path=/head/; revision=78785
@ -208,7 +208,6 @@ static struct witness_order_list_entry order_lists[] = {
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{ "ng_worklist", &lock_class_mtx_spin },
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{ "ithread table lock", &lock_class_mtx_spin },
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{ "sched lock", &lock_class_mtx_spin },
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{ "clk", &lock_class_mtx_spin },
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{ "callout", &lock_class_mtx_spin },
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/*
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* leaf locks
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@ -220,6 +219,7 @@ static struct witness_order_list_entry order_lists[] = {
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#endif
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{ "smp rendezvous", &lock_class_mtx_spin },
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#endif
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{ "clk", &lock_class_mtx_spin },
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{ NULL, NULL },
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{ NULL, NULL }
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};
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@ -284,6 +284,7 @@ witness_initialize(void *dummy __unused)
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mtx_unlock(&Giant);
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mtx_assert(&Giant, MA_NOTOWNED);
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CTR1(KTR_WITNESS, "%s: initializing witness", __func__);
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STAILQ_INSERT_HEAD(&all_locks, &all_mtx.mtx_object, lo_list);
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mtx_init(&w_mtx, "witness lock", MTX_SPIN | MTX_QUIET | MTX_NOWITNESS);
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for (i = 0; i < WITNESS_COUNT; i++)
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@ -380,6 +381,8 @@ witness_destroy(struct lock_object *lock)
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mtx_lock_spin(&w_mtx);
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w->w_refcount--;
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if (w->w_refcount == 0) {
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CTR1(KTR_WITNESS, "Marking witness %s as dead",
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w->w_name);
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w->w_name = "(dead)";
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w->w_file = "(dead)";
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w->w_line = 0;
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@ -538,6 +541,9 @@ witness_lock(struct lock_object *lock, int flags, const char *file, int line)
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lock1->li_line);
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panic("recurse");
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}
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CTR3(KTR_WITNESS, "witness_lock: pid %d recursed on %s r=%d",
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curproc->p_pid, lock->lo_name,
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lock1->li_flags & LI_RECURSEMASK);
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lock1->li_file = file;
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lock1->li_line = line;
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return;
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@ -662,6 +668,8 @@ witness_lock(struct lock_object *lock, int flags, const char *file, int line)
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}
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}
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lock1 = &(*lock_list)->ll_children[(*lock_list)->ll_count - 1];
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CTR2(KTR_WITNESS, "Adding %s as a child of %s", lock->lo_name,
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lock1->li_lock->lo_name);
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if (!itismychild(lock1->li_lock->lo_witness, w))
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mtx_unlock_spin(&w_mtx);
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@ -675,11 +683,13 @@ out:
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lle = *lock_list;
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if (lle == NULL || lle->ll_count == LOCK_NCHILDREN) {
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*lock_list = witness_lock_list_get();
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if (*lock_list == NULL)
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lle = witness_lock_list_get();
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if (lle == NULL)
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return;
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(*lock_list)->ll_next = lle;
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lle = *lock_list;
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lle->ll_next = *lock_list;
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CTR2(KTR_WITNESS, "witness_lock: pid %d added lle %p",
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curproc->p_pid, lle);
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*lock_list = lle;
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}
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lock1 = &lle->ll_children[lle->ll_count++];
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lock1->li_lock = lock;
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@ -689,6 +699,8 @@ out:
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lock1->li_flags = LI_EXCLUSIVE;
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else
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lock1->li_flags = 0;
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CTR3(KTR_WITNESS, "witness_lock: pid %d added %s as lle[%d]",
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curproc->p_pid, lock->lo_name, lle->ll_count - 1);
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}
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void
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@ -698,6 +710,7 @@ witness_unlock(struct lock_object *lock, int flags, const char *file, int line)
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struct lock_instance *instance;
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struct lock_class *class;
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struct proc *p;
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critical_t s;
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int i, j;
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if (witness_cold || witness_dead || lock->lo_witness == NULL ||
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@ -739,16 +752,30 @@ witness_unlock(struct lock_object *lock, int flags, const char *file, int line)
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}
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/* If we are recursed, unrecurse. */
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if ((instance->li_flags & LI_RECURSEMASK) > 0) {
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CTR3(KTR_WITNESS,
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"witness_unlock: pid %d unrecursed on %s r=%d",
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curproc->p_pid,
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instance->li_lock->lo_name,
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instance->li_flags);
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instance->li_flags--;
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goto out;
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}
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s = critical_enter();
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CTR3(KTR_WITNESS,
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"witness_unlock: pid %d removed %s from lle[%d]",
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curproc->p_pid, instance->li_lock->lo_name,
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(*lock_list)->ll_count - 1);
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(*lock_list)->ll_count--;
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for (j = i; j < (*lock_list)->ll_count; j++)
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(*lock_list)->ll_children[j] =
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(*lock_list)->ll_children[j + 1];
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critical_exit(s);
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if ((*lock_list)->ll_count == 0) {
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lle = *lock_list;
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*lock_list = lle->ll_next;
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CTR2(KTR_WITNESS,
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"witness_unlock: pid %d removed lle %p",
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curproc->p_pid, lle);
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witness_lock_list_free(lle);
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}
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goto out;
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@ -803,8 +830,14 @@ again:
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lock1->li_lock == &Giant.mtx_object)
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continue;
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if ((lock1->li_lock->lo_flags & LO_SLEEPABLE) != 0) {
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if (check_only == 0)
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if (check_only == 0) {
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CTR3(KTR_WITNESS,
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"pid %d: sleeping with (%s) %s held",
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curproc->p_pid,
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lock1->li_lock->lo_class->lc_name,
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lock1->li_lock->lo_name);
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lock1->li_flags |= LI_SLEPT;
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}
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continue;
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}
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n++;
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