The patch titled
Subject: mm/hugetlb: sort out global lock annotations
has been added to the -mm mm-unstable branch. Its filename is
mm-hugetlb-sort-out-global-lock-annotations.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-hugetlb-sort-out-global-lock-annotations.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Mateusz Guzik <mjguzik@xxxxxxxxx>
Subject: mm/hugetlb: sort out global lock annotations
Date: Wed, 28 Aug 2024 18:07:04 +0200
The mutex array pointer shares a cacheline with the spinlock:
ffffffff84187480 B hugetlb_fault_mutex_table
ffffffff84187488 B hugetlb_lock
This is because the former is annotated with a macro forcing cacheline
alignment. I suspect it was meant to be the variant which on top of it
makes sure the object does not share the cacheline with anyone.
Since array pointer itself is de facto read-only such an annotation does
not make sense there anyway. Instead mark it __ro_after_init along with
the size var.
Do however move the spinlock out of the way.
Link: https://lkml.kernel.org/r/20240828160704.1425767-1-mjguzik@xxxxxxxxx
Signed-off-by: Mateusz Guzik <mjguzik@xxxxxxxxx>
Cc: Davidlohr Bueso <dave@xxxxxxxxxxxx>
Cc: Muchun Song <muchun.song@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/hugetlb.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
--- a/mm/hugetlb.c~mm-hugetlb-sort-out-global-lock-annotations
+++ a/mm/hugetlb.c
@@ -72,14 +72,14 @@ static unsigned int default_hugepages_in
* Protects updates to hugepage_freelists, hugepage_activelist, nr_huge_pages,
* free_huge_pages, and surplus_huge_pages.
*/
-DEFINE_SPINLOCK(hugetlb_lock);
+__cacheline_aligned_in_smp DEFINE_SPINLOCK(hugetlb_lock);
/*
* Serializes faults on the same logical page. This is used to
* prevent spurious OOMs when the hugepage pool is fully utilized.
*/
-static int num_fault_mutexes;
-struct mutex *hugetlb_fault_mutex_table ____cacheline_aligned_in_smp;
+static __ro_after_init int num_fault_mutexes;
+__ro_after_init struct mutex *hugetlb_fault_mutex_table;
/* Forward declaration */
static int hugetlb_acct_memory(struct hstate *h, long delta);
_
Patches currently in -mm which might be from mjguzik@xxxxxxxxx are
mm-hugetlb-sort-out-global-lock-annotations.patch
ratelimit-convert-flags-to-int-to-save-8-bytes-in-size.patch
