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

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

[guoren]

From: Guo Ren <guoren@linux.alibaba.com>

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 <guoren@linux.alibaba.com>
Signed-off-by: Guo Ren <guoren@kernel.org>
Acked-by: Palmer Dabbelt <palmer@rivosinc.com>
Reviewed-by: Masami Hiramatsu <mhiramat@kernel.org>
Cc: <stable@vger.kernel.org>
---
 arch/riscv/kernel/patch.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/riscv/kernel/patch.c b/arch/riscv/kernel/patch.c
index 0b552873a577..765004b60513 100644
--- a/arch/riscv/kernel/patch.c
+++ b/arch/riscv/kernel/patch.c
@@ -104,7 +104,7 @@ static int patch_text_cb(void *data)
 	struct patch_insn *patch = data;
 	int ret = 0;
 
-	if (atomic_inc_return(&patch->cpu_count) == 1) {
+	if (atomic_inc_return(&patch->cpu_count) == num_online_cpus()) {
 		ret =
 		    patch_text_nosync(patch->addr, &patch->insn,
 					    GET_INSN_LENGTH(patch->insn));
-- 
2.25.1

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

[Greg KH]

On Wed, Apr 06, 2022 at 10:16:49PM +0800, guoren@kernel.org wrote:
> From: Guo Ren <guoren@linux.alibaba.com>
> 
> 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 <guoren@linux.alibaba.com>
> Signed-off-by: Guo Ren <guoren@kernel.org>
> Acked-by: Palmer Dabbelt <palmer@rivosinc.com>
> Reviewed-by: Masami Hiramatsu <mhiramat@kernel.org>
> Cc: <stable@vger.kernel.org>
> ---
>  arch/riscv/kernel/patch.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)

What commit id does this change fix?

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

[Palmer Dabbelt]

On Wed, 06 Apr 2022 11:13:36 PDT (-0700), Greg KH wrote:
> On Wed, Apr 06, 2022 at 10:16:49PM +0800, guoren@kernel.org wrote:
>> From: Guo Ren <guoren@linux.alibaba.com>
>>
>> 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 <guoren@linux.alibaba.com>
>> Signed-off-by: Guo Ren <guoren@kernel.org>
>> Acked-by: Palmer Dabbelt <palmer@rivosinc.com>
>> Reviewed-by: Masami Hiramatsu <mhiramat@kernel.org>
>> Cc: <stable@vger.kernel.org>
>> ---
>>  arch/riscv/kernel/patch.c | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> What commit id does this change fix?

I think it's been there since the beginning of our text patching, so

Fixes: 043cb41a85de ("riscv: introduce interfaces to patch kernel code")

seems like the best bet, but I'll go take another look before merging 
it.  That's confusing here, as I acked it, but that was for an earlier 
version that touched more than one arch so it was more ambiguous as to 
which tree it was going through (IIRC I said one of those "LMK if you 
want it through my tree, but here's an Ack in case someone else wants to 
take it" sort of things, as I usually do when it's ambiguous).

Without a changelog, cover letter, or the other patches in the set it's 
kind of hard to tell, though ;)

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

[Guo Ren]

On Thu, Apr 7, 2022 at 3:06 AM Palmer Dabbelt <palmer@rivosinc.com> wrote:
>
> On Wed, 06 Apr 2022 11:13:36 PDT (-0700), Greg KH wrote:
> > On Wed, Apr 06, 2022 at 10:16:49PM +0800, guoren@kernel.org wrote:
> >> From: Guo Ren <guoren@linux.alibaba.com>
> >>
> >> 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 <guoren@linux.alibaba.com>
> >> Signed-off-by: Guo Ren <guoren@kernel.org>
> >> Acked-by: Palmer Dabbelt <palmer@rivosinc.com>
> >> Reviewed-by: Masami Hiramatsu <mhiramat@kernel.org>
> >> Cc: <stable@vger.kernel.org>
> >> ---
> >>  arch/riscv/kernel/patch.c | 2 +-
> >>  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > What commit id does this change fix?
>
> I think it's been there since the beginning of our text patching, so
>
> Fixes: 043cb41a85de ("riscv: introduce interfaces to patch kernel code")
Yes, it the riscv origin.

>
> seems like the best bet, but I'll go take another look before merging
> it.  That's confusing here, as I acked it, but that was for an earlier
> version that touched more than one arch so it was more ambiguous as to
> which tree it was going through (IIRC I said one of those "LMK if you
> want it through my tree, but here's an Ack in case someone else wants to
> take it" sort of things, as I usually do when it's ambiguous).
Thx for the clarification, I would remove the acked in the next version.

>
> Without a changelog, cover letter, or the other patches in the set it's
> kind of hard to tell, though ;)
Okay, I should add a changelog for the patch with cover letter.


-- 
Best Regards
 Guo Ren

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

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

[Guo Ren]

On Thu, Apr 7, 2022 at 2:13 AM Greg KH <gregkh@linuxfoundation.org> wrote:
>
> On Wed, Apr 06, 2022 at 10:16:49PM +0800, guoren@kernel.org wrote:
> > From: Guo Ren <guoren@linux.alibaba.com>
> >
> > 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 <guoren@linux.alibaba.com>
> > Signed-off-by: Guo Ren <guoren@kernel.org>
> > Acked-by: Palmer Dabbelt <palmer@rivosinc.com>
> > Reviewed-by: Masami Hiramatsu <mhiramat@kernel.org>
> > Cc: <stable@vger.kernel.org>
> > ---
> >  arch/riscv/kernel/patch.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
>
> What commit id does this change fix?
Thx for pointing this out, I would follow the rule to add Cc:
<stable@vger.kernel.org>.

>


-- 
Best Regards
 Guo Ren

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

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

[Palmer Dabbelt]

On Wed, 06 Apr 2022 07:16:49 PDT (-0700), guoren@kernel.org wrote:
> From: Guo Ren <guoren@linux.alibaba.com>
>
> 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 <guoren@linux.alibaba.com>
> Signed-off-by: Guo Ren <guoren@kernel.org>
> Acked-by: Palmer Dabbelt <palmer@rivosinc.com>
> Reviewed-by: Masami Hiramatsu <mhiramat@kernel.org>
> Cc: <stable@vger.kernel.org>
> ---
>  arch/riscv/kernel/patch.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/riscv/kernel/patch.c b/arch/riscv/kernel/patch.c
> index 0b552873a577..765004b60513 100644
> --- a/arch/riscv/kernel/patch.c
> +++ b/arch/riscv/kernel/patch.c
> @@ -104,7 +104,7 @@ static int patch_text_cb(void *data)
>  	struct patch_insn *patch = data;
>  	int ret = 0;
>
> -	if (atomic_inc_return(&patch->cpu_count) == 1) {
> +	if (atomic_inc_return(&patch->cpu_count) == num_online_cpus()) {
>  		ret =
>  		    patch_text_nosync(patch->addr, &patch->insn,
>  					    GET_INSN_LENGTH(patch->insn));

Thanks, this is on fixes.

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

[Palmer Dabbelt]

On Thu, 21 Apr 2022 15:57:32 PDT (-0700), Palmer Dabbelt wrote:
> On Wed, 06 Apr 2022 07:16:49 PDT (-0700), guoren@kernel.org wrote:
>> From: Guo Ren <guoren@linux.alibaba.com>
>>
>> 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 <guoren@linux.alibaba.com>
>> Signed-off-by: Guo Ren <guoren@kernel.org>
>> Acked-by: Palmer Dabbelt <palmer@rivosinc.com>
>> Reviewed-by: Masami Hiramatsu <mhiramat@kernel.org>
>> Cc: <stable@vger.kernel.org>
>> ---
>>  arch/riscv/kernel/patch.c | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/arch/riscv/kernel/patch.c b/arch/riscv/kernel/patch.c
>> index 0b552873a577..765004b60513 100644
>> --- a/arch/riscv/kernel/patch.c
>> +++ b/arch/riscv/kernel/patch.c
>> @@ -104,7 +104,7 @@ static int patch_text_cb(void *data)
>>  	struct patch_insn *patch = data;
>>  	int ret = 0;
>>
>> -	if (atomic_inc_return(&patch->cpu_count) == 1) {
>> +	if (atomic_inc_return(&patch->cpu_count) == num_online_cpus()) {
>>  		ret =
>>  		    patch_text_nosync(patch->addr, &patch->insn,
>>  					    GET_INSN_LENGTH(patch->insn));
>
> Thanks, this is on fixes.

Sorry, I forgot to add the Fixes and stable tags.  I just fixed that up, 
but I'm going to hold off on this one until next week's PR to make sure 
it has time to go through linux-next.

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

[Guo Ren]

On Sat, Apr 23, 2022 at 12:02 AM Palmer Dabbelt <palmer@dabbelt.com> wrote:
>
> On Thu, 21 Apr 2022 15:57:32 PDT (-0700), Palmer Dabbelt wrote:
> > On Wed, 06 Apr 2022 07:16:49 PDT (-0700), guoren@kernel.org wrote:
> >> From: Guo Ren <guoren@linux.alibaba.com>
> >>
> >> 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 <guoren@linux.alibaba.com>
> >> Signed-off-by: Guo Ren <guoren@kernel.org>
> >> Acked-by: Palmer Dabbelt <palmer@rivosinc.com>
> >> Reviewed-by: Masami Hiramatsu <mhiramat@kernel.org>
> >> Cc: <stable@vger.kernel.org>
> >> ---
> >>  arch/riscv/kernel/patch.c | 2 +-
> >>  1 file changed, 1 insertion(+), 1 deletion(-)
> >>
> >> diff --git a/arch/riscv/kernel/patch.c b/arch/riscv/kernel/patch.c
> >> index 0b552873a577..765004b60513 100644
> >> --- a/arch/riscv/kernel/patch.c
> >> +++ b/arch/riscv/kernel/patch.c
> >> @@ -104,7 +104,7 @@ static int patch_text_cb(void *data)
> >>      struct patch_insn *patch = data;
> >>      int ret = 0;
> >>
> >> -    if (atomic_inc_return(&patch->cpu_count) == 1) {
> >> +    if (atomic_inc_return(&patch->cpu_count) == num_online_cpus()) {
> >>              ret =
> >>                  patch_text_nosync(patch->addr, &patch->insn,
> >>                                          GET_INSN_LENGTH(patch->insn));
> >
> > Thanks, this is on fixes.
>
> Sorry, I forgot to add the Fixes and stable tags.  I just fixed that up,
> but I'm going to hold off on this one until next week's PR to make sure
> it has time to go through linux-next.

https://lore.kernel.org/linux-riscv/20220407073323.743224-3-guoren@kernel.org/

-- 
Best Regards
 Guo Ren

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