rcu: Add lockdep_assert_held() teeth to tree_plugin.h

Comments can be helpful, but assertions carry more force.  This commit
therefore adds lockdep_assert_held() and RCU_LOCKDEP_WARN() calls to
enforce lock-held and interrupt-disabled preconditions.

Reported-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
index 9cb3dff78b6fdff3d3b661ab4d66fc7bdec3fc30..ee7cea75273eb96347ca2a071d359fb3f6c97d57 100644 (file)
--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -181,6 +181,8 @@ static void rcu_preempt_ctxt_queue(struct rcu_node *rnp, struct rcu_data *rdp)
                         (rnp->expmask & rdp->grpmask ? RCU_EXP_BLKD : 0);
        struct task_struct *t = current;
 
+       lockdep_assert_held(&rnp->lock);
+
        /*
         * Decide where to queue the newly blocked task.  In theory,
         * this could be an if-statement.  In practice, when I tried
@@ -289,6 +291,7 @@ static void rcu_preempt_ctxt_queue(struct rcu_node *rnp, struct rcu_data *rdp)
  */
 static void rcu_preempt_qs(void)
 {
+       RCU_LOCKDEP_WARN(preemptible(), "rcu_preempt_qs() invoked with preemption enabled!!!\n");
        if (__this_cpu_read(rcu_data_p->cpu_no_qs.s)) {
                trace_rcu_grace_period(TPS("rcu_preempt"),
                                       __this_cpu_read(rcu_data_p->gpnum),
@@ -318,6 +321,7 @@ static void rcu_preempt_note_context_switch(bool preempt)
        struct rcu_data *rdp;
        struct rcu_node *rnp;
 
+       RCU_LOCKDEP_WARN(!irqs_disabled(), "rcu_preempt_note_context_switch() invoked with interrupts enabled!!!\n");
        WARN_ON_ONCE(!preempt && t->rcu_read_lock_nesting > 0);
        if (t->rcu_read_lock_nesting > 0 &&
            !t->rcu_read_unlock_special.b.blocked) {
@@ -634,6 +638,7 @@ static int rcu_print_task_exp_stall(struct rcu_node *rnp)
  */
 static void rcu_preempt_check_blocked_tasks(struct rcu_node *rnp)
 {
+       RCU_LOCKDEP_WARN(preemptible(), "rcu_preempt_check_blocked_tasks() invoked with preemption enabled!!!\n");
        WARN_ON_ONCE(rcu_preempt_blocked_readers_cgp(rnp));
        if (rcu_preempt_has_tasks(rnp))
                rnp->gp_tasks = rnp->blkd_tasks.next;
@@ -1024,6 +1029,7 @@ static void rcu_initiate_boost(struct rcu_node *rnp, unsigned long flags)
 {
        struct task_struct *t;
 
+       lockdep_assert_held(&rnp->lock);
        if (!rcu_preempt_blocked_readers_cgp(rnp) && rnp->exp_tasks == NULL) {
                rnp->n_balk_exp_gp_tasks++;
                raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
@@ -1404,6 +1410,7 @@ int rcu_needs_cpu(u64 basemono, u64 *nextevt)
        struct rcu_dynticks *rdtp = this_cpu_ptr(&rcu_dynticks);
        unsigned long dj;
 
+       RCU_LOCKDEP_WARN(!irqs_disabled(), "rcu_needs_cpu() invoked with irqs enabled!!!");
        if (IS_ENABLED(CONFIG_RCU_NOCB_CPU_ALL)) {
                *nextevt = KTIME_MAX;
                return 0;
@@ -1456,6 +1463,7 @@ static void rcu_prepare_for_idle(void)
        struct rcu_state *rsp;
        int tne;
 
+       RCU_LOCKDEP_WARN(!irqs_disabled(), "rcu_prepare_for_idle() invoked with irqs enabled!!!");
        if (IS_ENABLED(CONFIG_RCU_NOCB_CPU_ALL) ||
            rcu_is_nocb_cpu(smp_processor_id()))
                return;
@@ -1511,6 +1519,7 @@ static void rcu_prepare_for_idle(void)
  */
 static void rcu_cleanup_after_idle(void)
 {
+       RCU_LOCKDEP_WARN(!irqs_disabled(), "rcu_cleanup_after_idle() invoked with irqs enabled!!!");
        if (IS_ENABLED(CONFIG_RCU_NOCB_CPU_ALL) ||
            rcu_is_nocb_cpu(smp_processor_id()))
                return;
@@ -2544,6 +2553,8 @@ static void rcu_sysidle_enter(int irq)
        unsigned long j;
        struct rcu_dynticks *rdtp = this_cpu_ptr(&rcu_dynticks);
 
+       RCU_LOCKDEP_WARN(!irqs_disabled(), "rcu_sysidle_enter() invoked with irqs enabled!!!");
+
        /* If there are no nohz_full= CPUs, no need to track this. */
        if (!tick_nohz_full_enabled())
                return;
@@ -2615,6 +2626,8 @@ static void rcu_sysidle_exit(int irq)
 {
        struct rcu_dynticks *rdtp = this_cpu_ptr(&rcu_dynticks);
 
+       RCU_LOCKDEP_WARN(!irqs_disabled(), "rcu_sysidle_exit() invoked with irqs enabled!!!");
+
        /* If there are no nohz_full= CPUs, no need to track this. */
        if (!tick_nohz_full_enabled())
                return;
@@ -2674,6 +2687,8 @@ static void rcu_sysidle_check_cpu(struct rcu_data *rdp, bool *isidle,
        unsigned long j;
        struct rcu_dynticks *rdtp = rdp->dynticks;
 
+       RCU_LOCKDEP_WARN(!irqs_disabled(), "rcu_sysidle_check_cpu() invoked with irqs enabled!!!");
+
        /* If there are no nohz_full= CPUs, don't check system-wide idleness. */
        if (!tick_nohz_full_enabled())
                return;
@@ -2842,6 +2857,8 @@ bool rcu_sys_is_idle(void)
        static struct rcu_sysidle_head rsh;
        int rss = READ_ONCE(full_sysidle_state);
 
+       RCU_LOCKDEP_WARN(!irqs_disabled(), "rcu_sys_is_idle() invoked with irqs enabled!!!");
+
        if (WARN_ON_ONCE(smp_processor_id() != tick_do_timer_cpu))
                return false;