[PATCH] mm: Pair atomic_read_release() with _acquire()

[Linus Walleij]

The code for syncing vmalloc memory PGD pointers is using
atomic_read() in pair with atomic_read_release() but the
proper pairing is atomic_read_acquire() paired with
atomic_read_release().

Fixes: d31e23aff011 ("ARM: mm: make vmalloc_seq handling SMP safe")
Suggested-by: Mark Rutland <mark.rutland at arm.com>
Signed-off-by: Linus Walleij <linus.walleij at linaro.org>
---
This patch was done on top of Melon Liu's patch:
https://www.arm.linux.org.uk/developer/patches/viewpatch.php?id=9427/1
---
 arch/arm/mm/ioremap.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/arm/mm/ioremap.c b/arch/arm/mm/ioremap.c
index f952b0b0f8a5..257ed86f3474 100644
--- a/arch/arm/mm/ioremap.c
+++ b/arch/arm/mm/ioremap.c
@@ -138,7 +138,7 @@ void __check_vmalloc_seq(struct mm_struct *mm)
 	int seq;
 
 	do {
-		seq = atomic_read(&init_mm.context.vmalloc_seq);
+		seq = atomic_read_acquire(&init_mm.context.vmalloc_seq);
 		sync_vmalloc_pgds(mm);
 		/*
 		 * Use a store-release so that other CPUs that observe the

---
base-commit: d530f55d9fde0aae4ac90e072b288da13f6aae81
change-id: 20241021-atomic-read-acquire-52a667991cfc

Best regards,
-- 
Linus Walleij <linus.walleij at linaro.org>