On 2022/4/12 10:07, ying.huang@xxxxxxxxx wrote:
> On Sat, 2022-04-09 at 15:38 +0800, Miaohe Lin wrote:
>> rcu_read_lock is required by grabbing the task refcount but it's not
>> needed for ptrace_may_access. So we could release the rcu lock after
>> task refcount is successfully grabbed to reduce the rcu holding time.
>>
>> Reviewed-by: Muchun Song <songmuchun@xxxxxxxxxxxxx>
>> Signed-off-by: Miaohe Lin <linmiaohe@xxxxxxxxxx>
>> ---
>> mm/migrate.c | 3 +--
>> 1 file changed, 1 insertion(+), 2 deletions(-)
>>
>> diff --git a/mm/migrate.c b/mm/migrate.c
>> index a3d8c2be2631..d8aae6c75990 100644
>> --- a/mm/migrate.c
>> +++ b/mm/migrate.c
>> @@ -1907,17 +1907,16 @@ static struct mm_struct *find_mm_struct(pid_t pid, nodemask_t *mem_nodes)
>> return ERR_PTR(-ESRCH);
>> }
>> get_task_struct(task);
>> + rcu_read_unlock();
>>
>>
>> /*
>> * Check if this process has the right to modify the specified
>> * process. Use the regular "ptrace_may_access()" checks.
>> */
>> if (!ptrace_may_access(task, PTRACE_MODE_READ_REALCREDS)) {
>> - rcu_read_unlock();
>> mm = ERR_PTR(-EPERM);
>> goto out;
>> }
>> - rcu_read_unlock();
>>
>>
>> mm = ERR_PTR(security_task_movememory(task));
>> if (IS_ERR(mm))
>
> Why do you ignore our discussion for the previous version?
>
> https://lore.kernel.org/linux-mm/8735ju7as9.fsf@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx/
>
Sorry for confusing. I remember this patch is pending for verify. The reason I post this series is that
I want to move the other patches in this series forward while this patch is still pending for verify.
Thanks.
> Best Regards,
> Huang, Ying
>
>
> .
>
