| Message ID | 20241021-atomic-read-acquire-v1-1-4dee71191c06@linaro.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | mm: Pair atomic_read_release() with _acquire() | expand |
Hi Linus, On Mon, 21 Oct 2024 at 10:53, Linus Walleij <linus.walleij@linaro.org> wrote: > > 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(). > atomic_read_release() does not exist. Maybe explain here that the read_acquire() prevents sync_vmalloc_pgds() from observing stale init_mm contents? > Fixes: d31e23aff011 ("ARM: mm: make vmalloc_seq handling SMP safe") > Suggested-by: Mark Rutland <mark.rutland@arm.com> > Signed-off-by: Linus Walleij <linus.walleij@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@linaro.org> >
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
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@arm.com> Signed-off-by: Linus Walleij <linus.walleij@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(-) --- base-commit: d530f55d9fde0aae4ac90e072b288da13f6aae81 change-id: 20241021-atomic-read-acquire-52a667991cfc Best regards,