The following commit has been merged into the smp/core branch of tip:

Commit-ID:     947c397f5991b8ba9b5de2a5d3fb109ce663e75c
Gitweb:        https://git.kernel.org/tip/947c397f5991b8ba9b5de2a5d3fb109ce663e75c
Author:        Chuyi Zhou <zhouchuyi@bytedance.com>
AuthorDate:    Thu, 09 Jul 2026 20:29:27 +08:00
Committer:     Thomas Gleixner <tglx@kernel.org>
CommitterDate: Thu, 16 Jul 2026 09:24:55 +02:00

smp: Remove preempt_disable() from on_each_cpu_cond_mask()

smp_call_function_many_cond() handles the preemption and CPU pinning
requirements internally. on_each_cpu_cond_mask() only builds the call
flags and forwards the request to that helper.

Remove the outer preempt_disable() and preempt_enable() pair from
on_each_cpu_cond_mask().

Signed-off-by: Chuyi Zhou <zhouchuyi@bytedance.com>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Tested-by: Paul E. McKenney <paulmck@kernel.org>
Reviewed-by: Muchun Song <muchun.song@linux.dev>
Reviewed-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Link: https://patch.msgid.link/20260709122933.4021501-9-zhouchuyi@bytedance.com
---
 kernel/smp.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/kernel/smp.c b/kernel/smp.c
index 6c4c93e..6f8f4c9 100644
--- a/kernel/smp.c
+++ b/kernel/smp.c
@@ -1126,12 +1126,14 @@ void __init smp_init(void)
  * @func:	The function to run on all applicable CPUs.
  *		This must be fast and non-blocking.
  * @info:	An arbitrary pointer to pass to both functions.
- * @wait:	If true, wait (atomically) until function has
- *		completed on other CPUs.
+ * @wait:	If true, wait until function has completed on other CPUs.
  * @mask:	The set of cpus to run on (only runs on online subset).
  *
- * Preemption is disabled to protect against CPUs going offline but not online.
- * CPUs going online during the call will not be seen or sent an IPI.
+ * Target CPU selection and work queueing are done with preemption
+ * disabled. This protects against CPUs going offline, but not against
+ * CPUs coming online concurrently; newly online CPUs are not guaranteed
+ * to be seen or sent an IPI. If @wait is true, the final wait for remote
+ * completion happens after that preemption-disabled section.
  *
  * You must not call this function with disabled interrupts or
  * from a hardware interrupt handler or from a bottom half handler.
@@ -1144,9 +1146,7 @@ void on_each_cpu_cond_mask(smp_cond_func_t cond_func, smp_call_func_t func,
 	if (wait)
 		scf_flags |= SCF_WAIT;
 
-	preempt_disable();
 	smp_call_function_many_cond(mask, func, info, scf_flags, cond_func);
-	preempt_enable();
 }
 EXPORT_SYMBOL(on_each_cpu_cond_mask);