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Message-ID: <175365568477.581055.6002001481718640290.tglx@xen13>
Date: Mon, 28 Jul 2025 00:37:56 +0200 (CEST)
From: Thomas Gleixner <tglx@...utronix.de>
To: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: linux-kernel@...r.kernel.org, x86@...nel.org
Subject: [GIT pull] smp/core for v6.17-rc1
Linus,
please pull the latest smp/core branch from:
git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git smp-core-2025-07-27
up to: 946a72819825: smp: Wait only if work was enqueued
A set of updates for SMP function calls:
- Improve localitu 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
Thanks,
tglx
------------------>
Rik van Riel (1):
smp: Wait only if work was enqueued
Viresh Kumar (1):
smp: Fix typo in comment for raw_smp_processor_id()
Yury Norov [NVIDIA] (3):
smp: Improve locality in smp_call_function_any()
smp: Use cpumask_any_but() in smp_call_function_many_cond()
smp: Defer check for local execution in smp_call_function_many_cond()
include/linux/smp.h | 2 +-
kernel/smp.c | 44 ++++++++++++++------------------------------
2 files changed, 15 insertions(+), 31 deletions(-)
diff --git a/include/linux/smp.h b/include/linux/smp.h
index f1aa0952e8c3..bea8d2826e09 100644
--- a/include/linux/smp.h
+++ b/include/linux/smp.h
@@ -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.
diff --git a/kernel/smp.c b/kernel/smp.c
index 974f3a3962e8..c5e1da7a88da 100644
--- a/kernel/smp.c
+++ b/kernel/smp.c
@@ -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;
-
- /* 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;
- }
+ if (!cpumask_test_cpu(cpu, mask))
+ cpu = sched_numa_find_nth_cpu(mask, 0, cpu_to_node(cpu));
- /* 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);
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