rcu: Delete a redundant check in rcu_check_gp_kthread_starvation()

The rcu_check_gp_kthread_starvation() function uses task_cpu() to sample
the last CPU that the grace-period kthread ran on, and task_cpu() samples
the thread_info structure's ->cpu field.  But this field will always
contain a number corresponding to a CPU that was online some time in
the past, thus never a negative number.  This invariant is checked by
a WARN_ON_ONCE() in set_task_cpu().

This means that if the grace-period kthread exists, that is, if the "gpk"
local variable is non-NULL, the "cpu" local variable will be non-negative.
This in turn means that the existing check for non-negative "cpu" is
redundant with the enclosing check for non-NULL "gpk".

This commit threefore removes the redundant check of "cpu".

Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>

diff --git a/kernel/rcu/tree_stall.h b/kernel/rcu/tree_stall.h
index 6f06dc12904adb289b17a3531f9deac0777e2e4b..b5ce0580074e740d24e3a2bb3d936f5c877e49e3 100644 (file)
--- a/kernel/rcu/tree_stall.h
+++ b/kernel/rcu/tree_stall.h
@@ -537,13 +537,11 @@ static void rcu_check_gp_kthread_starvation(void)
                        pr_err("\tUnless %s kthread gets sufficient CPU time, OOM is now expected behavior.\n", rcu_state.name);
                        pr_err("RCU grace-period kthread stack dump:\n");
                        sched_show_task(gpk);
-                       if (cpu >= 0) {
-                               if (cpu_is_offline(cpu)) {
-                                       pr_err("RCU GP kthread last ran on offline CPU %d.\n", cpu);
-                               } else  {
-                                       pr_err("Stack dump where RCU GP kthread last ran:\n");
-                                       dump_cpu_task(cpu);
-                               }
+                       if (cpu_is_offline(cpu)) {
+                               pr_err("RCU GP kthread last ran on offline CPU %d.\n", cpu);
+                       } else  {
+                               pr_err("Stack dump where RCU GP kthread last ran:\n");
+                               dump_cpu_task(cpu);
                        }
                        wake_up_process(gpk);
                }