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rcu: Delete a redundant check in rcu_check_gp_kthread_starvation()

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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>
This commit is contained in:
Zhen Lei 2023-07-12 23:15:56 +08:00 committed by Frederic Weisbecker
parent 0bb80ecc33
commit b934b7ff5e
1 changed files with 5 additions and 7 deletions
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12
kernel/rcu/tree_stall.h
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@ -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);
}