linux-kernel - Re: [PATCH v2] exit: combine work under lock in synchronize_group_exit() and coredump_task

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Message-ID: <CAGudoHEg3k96oNSK-kOe+3StBv3z86iMVQjPd1pn1=SjtPQUVA@mail.gmail.com>
Date: Wed, 19 Mar 2025 20:18:12 +0100
From: Mateusz Guzik <mjguzik@...il.com>
To: Oleg Nesterov <oleg@...hat.com>
Cc: akpm@...ux-foundation.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] exit: combine work under lock in synchronize_group_exit()
 and coredump_task_exit()

On Wed, Mar 19, 2025 at 8:10 PM Oleg Nesterov <oleg@...hat.com> wrote:
>
> On 03/19, Mateusz Guzik wrote:
> >
> > +     spin_lock_irq(&sighand->siglock);
> > +     synchronize_group_exit(tsk, code);
> > +     core_state = coredump_task_exit_prep(tsk);
> > +     spin_unlock_irq(&sighand->siglock);
>
> Well, but why do we need the new (and trivial) coredump_task_exit_prep?
>

it's not *needed*, i claim it is cleaner

but i'm not going to argue about this, i'll submit and updated patch
later this evening or tomorrow

> Can't synchronize_group_exit() be
>
>         static struct core_state *synchronize_group_exit(struct task_struct *tsk, long code)
>         {
>                 struct sighand_struct *sighand = tsk->sighand;
>                 struct signal_struct *signal = tsk->signal;
>                 struct core_state *core_state = NULL;
>
>                 spin_lock_irq(&sighand->siglock);
>                 signal->quick_threads--;
>                 if ((signal->quick_threads == 0) &&
>                     !(signal->flags & SIGNAL_GROUP_EXIT)) {
>                         signal->flags = SIGNAL_GROUP_EXIT;
>                         signal->group_exit_code = code;
>                         signal->group_stop_count = 0;
>                 }
>                 /*
>                  * Serialize with any possible pending coredump.
>                  * We must hold siglock around checking core_state
>                  * and setting PF_POSTCOREDUMP.  The core-inducing thread
>                  * will increment ->nr_threads for each thread in the
>                  * group without PF_POSTCOREDUMP set.
>                  */
>                 tsk->flags |= PF_POSTCOREDUMP;
>                 core_state = tsk->signal->core_state;
>                 spin_unlock_irq(&sighand->siglock);
>
>                 return core_state;
>         }
>
> ?
>
> No need to shift spin_lock_irq(siglock) from synchronize_group_exit() to do_exit(),
> no need to rename coredump_task_exit...
>
> Oleg.
>


-- 
Mateusz Guzik <mjguzik gmail.com>