srcu: Add DEBUG_OBJECTS_RCU_HEAD functionality

This commit adds DEBUG_OBJECTS_RCU_HEAD checking to detect call_srcu()
counterparts to double-free bugs.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c
index 0b6ea105d9f81a687b523b0a5e3f80638f4cbf26..c6e2a4a1628bf565561f71508fc50bde2014e91a 100644 (file)
--- a/kernel/rcu/srcutree.c
+++ b/kernel/rcu/srcutree.c
@@ -761,6 +761,13 @@ static bool srcu_might_be_idle(struct srcu_struct *sp)
        return true; /* With reasonable probability, idle! */
 }
 
+/*
+ * SRCU callback function to leak a callback.
+ */
+static void srcu_leak_callback(struct rcu_head *rhp)
+{
+}
+
 /*
  * Enqueue an SRCU callback on the srcu_data structure associated with
  * the current CPU and the specified srcu_struct structure, initiating
@@ -799,6 +806,12 @@ void __call_srcu(struct srcu_struct *sp, struct rcu_head *rhp,
        struct srcu_data *sdp;
 
        check_init_srcu_struct(sp);
+       if (debug_rcu_head_queue(rhp)) {
+               /* Probable double call_srcu(), so leak the callback. */
+               WRITE_ONCE(rhp->func, srcu_leak_callback);
+               WARN_ONCE(1, "call_srcu(): Leaked duplicate callback\n");
+               return;
+       }
        rhp->func = func;
        local_irq_save(flags);
        sdp = this_cpu_ptr(sp->sda);
@@ -973,9 +986,12 @@ void srcu_barrier(struct srcu_struct *sp)
                spin_lock_irq(&sdp->lock);
                atomic_inc(&sp->srcu_barrier_cpu_cnt);
                sdp->srcu_barrier_head.func = srcu_barrier_cb;
+               debug_rcu_head_queue(&sdp->srcu_barrier_head);
                if (!rcu_segcblist_entrain(&sdp->srcu_cblist,
-                                          &sdp->srcu_barrier_head, 0))
+                                          &sdp->srcu_barrier_head, 0)) {
+                       debug_rcu_head_unqueue(&sdp->srcu_barrier_head);
                        atomic_dec(&sp->srcu_barrier_cpu_cnt);
+               }
                spin_unlock_irq(&sdp->lock);
        }
 
@@ -1100,6 +1116,7 @@ static void srcu_invoke_callbacks(struct work_struct *work)
        spin_unlock_irq(&sdp->lock);
        rhp = rcu_cblist_dequeue(&ready_cbs);
        for (; rhp != NULL; rhp = rcu_cblist_dequeue(&ready_cbs)) {
+               debug_rcu_head_unqueue(rhp);
                local_bh_disable();
                rhp->func(rhp);
                local_bh_enable();