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

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Message-ID: <20250319190950.GF26879@redhat.com>
Date: Wed, 19 Mar 2025 20:09:50 +0100
From: Oleg Nesterov <oleg@...hat.com>
To: Mateusz Guzik <mjguzik@...il.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 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?

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.