2022-04-06 17:10:44

by Guo Ren

Subject: [PATCH V3] xtensa: patch_text: Fixup last cpu should be master

From: Guo Ren <[email protected]>

These patch_text implementations are using stop_machine_cpuslocked
infrastructure with atomic cpu_count. The original idea: When the
master CPU patch_text, the others should wait for it. But current
implementation is using the first CPU as master, which couldn't
guarantee the remaining CPUs are waiting. This patch changes the
last CPU as the master to solve the potential risk.

Signed-off-by: Guo Ren <[email protected]>
Signed-off-by: Guo Ren <[email protected]>
Reviewed-by: Max Filippov <[email protected]>
Reviewed-by: Masami Hiramatsu <[email protected]>
Cc: <[email protected]>
---
arch/xtensa/kernel/jump_label.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/xtensa/kernel/jump_label.c b/arch/xtensa/kernel/jump_label.c
index 0dde21e0d3de..ad1841cecdfb 100644
--- a/arch/xtensa/kernel/jump_label.c
+++ b/arch/xtensa/kernel/jump_label.c
@@ -40,7 +40,7 @@ static int patch_text_stop_machine(void *data)
{
struct patch *patch = data;

- if (atomic_inc_return(&patch->cpu_count) == 1) {
+ if (atomic_inc_return(&patch->cpu_count) == num_online_cpus()) {
local_patch_text(patch->addr, patch->data, patch->sz);
atomic_inc(&patch->cpu_count);
} else {
--
2.25.1

2022-04-07 20:08:13

by Max Filippov

Subject: Re: [PATCH V3] xtensa: patch_text: Fixup last cpu should be master

On Wed, Apr 6, 2022 at 7:28 AM <[email protected]> wrote:
>
> From: Guo Ren <[email protected]>
>
> These patch_text implementations are using stop_machine_cpuslocked
> infrastructure with atomic cpu_count. The original idea: When the
> master CPU patch_text, the others should wait for it. But current
> implementation is using the first CPU as master, which couldn't
> guarantee the remaining CPUs are waiting. This patch changes the
> last CPU as the master to solve the potential risk.
>
> Signed-off-by: Guo Ren <[email protected]>
> Signed-off-by: Guo Ren <[email protected]>
> Reviewed-by: Max Filippov <[email protected]>
> Reviewed-by: Masami Hiramatsu <[email protected]>
> Cc: <[email protected]>
> ---
> arch/xtensa/kernel/jump_label.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)

Thanks. Applied to my xtensa tree.

-- Max

2022-04-07 21:12:52

by Guo Ren

Subject: Re: [PATCH V3] xtensa: patch_text: Fixup last cpu should be master

On Thu, Apr 7, 2022 at 11:35 AM Max Filippov <[email protected]> wrote:
>
> On Wed, Apr 6, 2022 at 7:28 AM <[email protected]> wrote:
> >
> > From: Guo Ren <[email protected]>
> >
> > These patch_text implementations are using stop_machine_cpuslocked
> > infrastructure with atomic cpu_count. The original idea: When the
> > master CPU patch_text, the others should wait for it. But current
> > implementation is using the first CPU as master, which couldn't
> > guarantee the remaining CPUs are waiting. This patch changes the
> > last CPU as the master to solve the potential risk.
> >
> > Signed-off-by: Guo Ren <[email protected]>
> > Signed-off-by: Guo Ren <[email protected]>
> > Reviewed-by: Max Filippov <[email protected]>
> > Reviewed-by: Masami Hiramatsu <[email protected]>
> > Cc: <[email protected]>
> > ---
> > arch/xtensa/kernel/jump_label.c | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
>
> Thanks. Applied to my xtensa tree.
I've missed the "Fixes:" for [email protected], so I would update
v3 to fix it.

>
> -- Max



--
Best Regards
Guo Ren

ML: https://lore.kernel.org/linux-csky/