Commit b34111a8 authored by Linus Torvalds's avatar Linus Torvalds
Browse files

Merge tag 'smp-core-2025-07-27' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 

Pull smp updates from Thomas Gleixner:
 "A set of updates for SMP function calls:

   - Improve locality of smp_call_function_any() by utilizing
     sched_numa_find_nth_cpu() instead of picking a random CPU

   - Wait for work completion in smp_call_function_many_cond() only when
     there was actually work enqueued

   - Simplify functions by unutlizing the appropriate cpumask_*()
     interfaces

   - Trivial cleanups"

* tag 'smp-core-2025-07-27' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  smp: Wait only if work was enqueued
  smp: Defer check for local execution in smp_call_function_many_cond()
  smp: Use cpumask_any_but() in smp_call_function_many_cond()
  smp: Improve locality in smp_call_function_any()
  smp: Fix typo in comment for raw_smp_processor_id()
parents dba3ec9f 946a7281

include/linux/smp.h

+1 −1
Original line number Diff line number Diff line
@@ -234,7 +234,7 @@ static inline int get_boot_cpu_id(void) 
#endif /* !SMP */



/**

 * raw_processor_id() - get the current (unstable) CPU id

 * raw_smp_processor_id() - get the current (unstable) CPU id

 *

 * For then you know what you are doing and need an unstable

 * CPU id.

kernel/smp.c

+14 −30
Original line number Diff line number Diff line
@@ -741,32 +741,19 @@ EXPORT_SYMBOL_GPL(smp_call_function_single_async); 
 *

 * Selection preference:

 *	1) current cpu if in @mask

 *	2) any cpu of current node if in @mask

 *	3) any other online cpu in @mask

 *	2) nearest cpu in @mask, based on NUMA topology

 */

int smp_call_function_any(const struct cpumask *mask,

			  smp_call_func_t func, void *info, int wait)

{

	unsigned int cpu;

	const struct cpumask *nodemask;

	int ret;



	/* Try for same CPU (cheapest) */

	cpu = get_cpu();

	if (cpumask_test_cpu(cpu, mask))

		goto call;

	if (!cpumask_test_cpu(cpu, mask))

		cpu = sched_numa_find_nth_cpu(mask, 0, cpu_to_node(cpu));



	/* Try for same node. */

	nodemask = cpumask_of_node(cpu_to_node(cpu));

	for (cpu = cpumask_first_and(nodemask, mask); cpu < nr_cpu_ids;

	     cpu = cpumask_next_and(cpu, nodemask, mask)) {

		if (cpu_online(cpu))

			goto call;

	}



	/* Any online will do: smp_call_function_single handles nr_cpu_ids. */

	cpu = cpumask_any_and(mask, cpu_online_mask);

call:

	ret = smp_call_function_single(cpu, func, info, wait);

	put_cpu();

	return ret;
@@ -792,7 +779,6 @@ static void smp_call_function_many_cond(const struct cpumask *mask, 
	bool wait = scf_flags & SCF_WAIT;

	int nr_cpus = 0;

	bool run_remote = false;

	bool run_local = false;



	lockdep_assert_preemption_disabled();
@@ -814,19 +800,8 @@ static void smp_call_function_many_cond(const struct cpumask *mask, 
	 */

	WARN_ON_ONCE(!in_task());



	/* Check if we need local execution. */

	if ((scf_flags & SCF_RUN_LOCAL) && cpumask_test_cpu(this_cpu, mask) &&

	    (!cond_func || cond_func(this_cpu, info)))

		run_local = true;



	/* Check if we need remote execution, i.e., any CPU excluding this one. */

	cpu = cpumask_first_and(mask, cpu_online_mask);

	if (cpu == this_cpu)

		cpu = cpumask_next_and(cpu, mask, cpu_online_mask);

	if (cpu < nr_cpu_ids)

		run_remote = true;



	if (run_remote) {

	if (cpumask_any_and_but(mask, cpu_online_mask, this_cpu) < nr_cpu_ids) {

		cfd = this_cpu_ptr(&cfd_data);

		cpumask_and(cfd->cpumask, mask, cpu_online_mask);

		__cpumask_clear_cpu(this_cpu, cfd->cpumask);
@@ -840,6 +815,9 @@ static void smp_call_function_many_cond(const struct cpumask *mask, 
				continue;

			}



			/* Work is enqueued on a remote CPU. */

			run_remote = true;



			csd_lock(csd);

			if (wait)

				csd->node.u_flags |= CSD_TYPE_SYNC;
@@ -851,6 +829,10 @@ static void smp_call_function_many_cond(const struct cpumask *mask, 
#endif

			trace_csd_queue_cpu(cpu, _RET_IP_, func, csd);



			/*

			 * Kick the remote CPU if this is the first work

			 * item enqueued.

			 */

			if (llist_add(&csd->node.llist, &per_cpu(call_single_queue, cpu))) {

				__cpumask_set_cpu(cpu, cfd->cpumask_ipi);

				nr_cpus++;
@@ -869,7 +851,9 @@ static void smp_call_function_many_cond(const struct cpumask *mask, 
			send_call_function_ipi_mask(cfd->cpumask_ipi);

	}



	if (run_local) {

	/* Check if we need local execution. */

	if ((scf_flags & SCF_RUN_LOCAL) && cpumask_test_cpu(this_cpu, mask) &&

	    (!cond_func || cond_func(this_cpu, info))) {

		unsigned long flags;



		local_irq_save(flags);