git: 65cd5ed09b66 - stable/15 - NOTES: IPI_PREEMPTION: Fix documentation, applies to all architectures

From: Olivier Certner <olce_at_FreeBSD.org>
Date: Thu, 08 Oct 2026 12:21:46 UTC
The branch stable/15 has been updated by olce:

URL: https://cgit.FreeBSD.org/src/commit/?id=65cd5ed09b663e61ae60b40d038751dfee8e8e10

commit 65cd5ed09b663e61ae60b40d038751dfee8e8e10
Author:     Olivier Certner <olce@FreeBSD.org>
AuthorDate: 2026-09-24 16:04:35 +0000
Commit:     Olivier Certner <olce@FreeBSD.org>
CommitDate: 2026-10-08 12:20:07 +0000

    NOTES: IPI_PREEMPTION: Fix documentation, applies to all architectures
    
    Move its description into 'sys/conf/NOTES' and update it to match reality.
    
    Reviewed by:    scheduler (mchoo)
    MFC after:      3 days
    Sponsored by:   The FreeBSD Foundation
    Differential Revision:  https://reviews.freebsd.org/D60013
    
    (cherry picked from commit d972d832f580c307cdfd87d563a382f40877dd10)
---
 sys/conf/NOTES     | 6 ++++++
 sys/x86/conf/NOTES | 7 -------
 2 files changed, 6 insertions(+), 7 deletions(-)

diff --git a/sys/conf/NOTES b/sys/conf/NOTES
index 040df12b3408..63ccd85c2317 100644
--- a/sys/conf/NOTES
+++ b/sys/conf/NOTES
@@ -282,6 +282,12 @@ options 	SX_NOINLINE
 #	  and allows interrupt threads to run sooner rather than waiting.
 options 	PREEMPTION
 
+# IPI_PREEMPTION instructs the 4BSD scheduler to immediately preempt a thread
+# running on a specific CPU when a thread pinned there has higher priority,
+# instead of waiting for a return to userland.  It has no effect on other
+# schedulers (e.g., ULE).
+options 	IPI_PREEMPTION
+
 # SMP Debugging Options:
 #
 # CALLOUT_PROFILING enables rudimentary profiling of the callwheel data
diff --git a/sys/x86/conf/NOTES b/sys/x86/conf/NOTES
index 3e8793e9d1ae..4adbe3fa1309 100644
--- a/sys/x86/conf/NOTES
+++ b/sys/x86/conf/NOTES
@@ -28,13 +28,6 @@
 #####################################################################
 # SMP OPTIONS:
 #
-# Notes:
-#
-# IPI_PREEMPTION instructs the kernel to preempt threads running on other
-# CPUS if needed.  Relies on the PREEMPTION option
-
-# Optional:
-options 	IPI_PREEMPTION
 
 # Debugging options.
 #