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Commit 251c617c authored by Paul E. McKenney's avatar Paul E. McKenney
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rcu: Make expedited RCU-preempt stall warnings count accurately 



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: default avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
parent 28728dd3

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)