linux-kernel - Re: [PATCH V3] KSM: allow dedup all tasks memory

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Message-ID: <CAGqmi75sDjHRT0efM4RW06UQEXvfneGoOtahidbk_jaSMzXCxw@mail.gmail.com>
Date:   Tue, 13 Nov 2018 20:44:47 +0300
From:   Timofey Titovets <timofey.titovets@...esis.ru>
To:     oleksandr@...alenko.name
Cc:     linux-doc@...r.kernel.org,
        Linux Kernel <linux-kernel@...r.kernel.org>,
        linux-mm@...ck.org, Matthew Wilcox <willy@...radead.org>
Subject: Re: [PATCH V3] KSM: allow dedup all tasks memory

вт, 13 нояб. 2018 г. в 20:27, Oleksandr Natalenko <oleksandr@...alenko.name>:
>
> On 13.11.2018 18:10, Timofey Titovets wrote:
> > You mean try do something, like that right?
> >
> > read_lock(&tasklist_lock);
> >   <get reference to task>
> >   task_lock(task);
> > read_unlock(&tasklist_lock);
> >     last_pid = task_pid_nr(task);
> >     ksm_import_task_vma(task);
> >   task_unlock(task);
>
> No, task_lock() uses spin_lock() under the bonnet, so this will be the
> same.
>
> Since the sole reason you have to lock/acquire/get a reference to
> task_struct here is to prevent it from disappearing, I was thinking
> about using get_task_struct(), which just increases atomic
> task_struct.usage value (IOW, takes a reference). I *hope* this will be
> enough to prevent task_struct from disappearing in the meantime.
>
> Someone, correct me if I'm wrong.

That brilliant, i just missing that api.
That must do exactly what i want.

Thanks!

> --
>    Oleksandr Natalenko (post-factum)
>