Messages in this thread | | | Date | Mon, 10 Jul 2023 12:03:35 -0700 | From | "Paul E. McKenney" <> | Subject | Re: [PATCH 1/2] rcu: Delete a redundant check in rcu_check_gp_kthread_starvation() |
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On Wed, Jul 05, 2023 at 03:30:19PM +0800, Zhen Lei wrote: > The above condition "if (gpk)" already ensures that gp_kthread is created, > so the local variable 'cpu' cannot be negative here. > > Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com> > --- > kernel/rcu/tree_stall.h | 12 +++++------- > 1 file changed, 5 insertions(+), 7 deletions(-) > > diff --git a/kernel/rcu/tree_stall.h b/kernel/rcu/tree_stall.h > index b10b8349bb2a48b..dcfaa3d5db2cbc7 100644 > --- 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) {
I am not quite this trusting of the relation between the relationship between the existence of the grace-period khread and its CPU number being in range. Let's please start with something like this:
if (!WARN_ON_ONCE(cpu < 0)) {
Please note that this is not just me. See for example the use of the cpumask_check() function, albeit the opposite concern.
> - 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); > } > -- > 2.25.1 >
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