rcu: Make expedited RCU-preempt stall warnings count accurately (251c617c) · Commits · 戴 / test

Currently, synchronize_sched_expedited_wait() simply sets the ndetected variable to the rcu_print_task_exp_stall() return value. This means that if the last rcu_node structure has no stalled tasks, record of any stalled tasks in previous rcu_node structures is lost, which can in turn result in failure to dump out the blocking rcu_node structures. Or could, had the test been correct. This commit therefore adds the return value of rcu_print_task_exp_stall() to ndetected and corrects the later test for ndetected. Signed-off-by:

Paul E. McKenney <paulmck@linux.vnet.ibm.com>

kernel/rcu/tree.c

+2 −2

Original line number	Diff line number	Diff line
		@@ -3778,7 +3778,7 @@ static void synchronize_sched_expedited_wait(struct rcu_state *rsp)
		rsp->name);
		ndetected = 0;
		rcu_for_each_leaf_node(rsp, rnp) {
		ndetected = rcu_print_task_exp_stall(rnp);
		ndetected += rcu_print_task_exp_stall(rnp);
		mask = 1;
		for (cpu = rnp->grplo; cpu <= rnp->grphi; cpu++, mask <<= 1) {
		struct rcu_data *rdp;
		@@ -3797,7 +3797,7 @@ static void synchronize_sched_expedited_wait(struct rcu_state *rsp)
		pr_cont(" } %lu jiffies s: %lu root: %#lx/%c\n",
		jiffies - jiffies_start, rsp->expedited_sequence,
		rnp_root->expmask, ".T"[!!rnp_root->exp_tasks]);
		if (!ndetected) {
		if (ndetected) {
		pr_err("blocking rcu_node structures:");
		rcu_for_each_node_breadth_first(rsp, rnp) {
		if (rnp == rnp_root)

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