rcu: Fix missing task information during rcu-preempt stall

The first item list_for_each_entry_continue(alist) iterates over is
alist->next, rather than alist itself. Consequently,
rcu_print_detail_task_stall_rnp() skips the task referenced by gp_tasks.

Use gp_tasks->prev as the argument to list_for_each_entry_continue()
instead.

Signed-off-by: Patrick Daly <pdaly@codeaurora.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 f8af20273868273427275aae1b0a03199cef08fc..853c7b8ea8332ebaf9446e38fdc76ae8a273bc22 100644 (file)
--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -395,7 +395,7 @@ static void rcu_print_detail_task_stall_rnp(struct rcu_node *rnp)
                raw_spin_unlock_irqrestore(&rnp->lock, flags);
                return;
        }
-       t = list_entry(rnp->gp_tasks,
+       t = list_entry(rnp->gp_tasks->prev,
                       struct task_struct, rcu_node_entry);
        list_for_each_entry_continue(t, &rnp->blkd_tasks, rcu_node_entry)
                sched_show_task(t);
@@ -452,7 +452,7 @@ static int rcu_print_task_stall(struct rcu_node *rnp)
        if (!rcu_preempt_blocked_readers_cgp(rnp))
                return 0;
        rcu_print_task_stall_begin(rnp);
-       t = list_entry(rnp->gp_tasks,
+       t = list_entry(rnp->gp_tasks->prev,
                       struct task_struct, rcu_node_entry);
        list_for_each_entry_continue(t, &rnp->blkd_tasks, rcu_node_entry) {
                pr_cont(" P%d", t->pid);