Commit b324696d authored by Linus Torvalds's avatar Linus Torvalds
Browse files

Merge tag 'csd-lock.2023.07.15a' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu 

Pull CSD lock updates from Paul McKenney:
 "This series reduces the number of stack traces dumped during CSD-lock
  debugging. This helps to avoid console overrun on systems with large
  numbers of CPUs"

* tag 'csd-lock.2023.07.15a' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu:
  smp: Reduce NMI traffic from CSD waiters to CSD destination
  smp: Reduce logging due to dump_stack of CSD waiters
parents 6ae0c157 0d3a00b3

kernel/smp.c

+11 −2
Original line number Diff line number Diff line
@@ -46,6 +46,8 @@ static DEFINE_PER_CPU_ALIGNED(struct call_function_data, cfd_data); 


static DEFINE_PER_CPU_SHARED_ALIGNED(struct llist_head, call_single_queue);



static DEFINE_PER_CPU(atomic_t, trigger_backtrace) = ATOMIC_INIT(1);



static void __flush_smp_call_function_queue(bool warn_cpu_offline);



int smpcfd_prepare_cpu(unsigned int cpu)
@@ -253,12 +255,14 @@ static bool csd_lock_wait_toolong(struct __call_single_data *csd, u64 ts0, u64 * 
			 *bug_id, !cpu_cur_csd ? "unresponsive" : "handling this request");

	}

	if (cpu >= 0) {

		if (atomic_cmpxchg_acquire(&per_cpu(trigger_backtrace, cpu), 1, 0))

			dump_cpu_task(cpu);

		if (!cpu_cur_csd) {

			pr_alert("csd: Re-sending CSD lock (#%d) IPI from CPU#%02d to CPU#%02d\n", *bug_id, raw_smp_processor_id(), cpu);

			arch_send_call_function_single_ipi(cpu);

		}

	}

	if (firsttime)

		dump_stack();

	*ts1 = ts2;
@@ -433,9 +437,14 @@ static void __flush_smp_call_function_queue(bool warn_cpu_offline) 
	struct llist_node *entry, *prev;

	struct llist_head *head;

	static bool warned;

	atomic_t *tbt;



	lockdep_assert_irqs_disabled();



	/* Allow waiters to send backtrace NMI from here onwards */

	tbt = this_cpu_ptr(&trigger_backtrace);

	atomic_set_release(tbt, 1);



	head = this_cpu_ptr(&call_single_queue);

	entry = llist_del_all(head);

	entry = llist_reverse_order(entry);