Re: [PATCH] ipc: optimize semget/shmget/msgget for lots of keys

From: Davidlohr Bueso <dave@stgolabs.net>
To: Guillaume Knispel <guillaume.knispel@supersonicimagine.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	Manfred Spraul <manfred@colorfullife.com>,
	Kees Cook <keescook@chromium.org>,
	Alexey Dobriyan <adobriyan@gmail.com>,
	"Eric W. Biederman" <ebiederm@xmission.com>,
	"Peter Zijlstra (Intel)" <peterz@infradead.org>,
	Ingo Molnar <mingo@kernel.org>,
	Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
	Serge Hallyn <serge@hallyn.com>, Andrey Vagin <avagin@openvz.org>,
	Marc Pardo <marc.pardo@supersonicimagine.com>,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH] ipc: optimize semget/shmget/msgget for lots of keys
Date: Wed, 2 Aug 2017 13:06:44 -0700	[thread overview]
Message-ID: <20170802200644.GA2395@linux-80c1.suse> (raw)
In-Reply-To: <20170731084237.GA123231@ubuntu>

On Mon, 31 Jul 2017, Guillaume Knispel wrote:
> static int __init ipc_init(void)
> {
>-	sem_init();
>-	msg_init();
>+	int err_sem, err_msg;
>+
>+	err_sem = sem_init();
>+	WARN(err_sem, "ipc: sysV sem_init failed: %d\n", err_sem);
>+	err_msg = msg_init();
>+	WARN(err_msg, "ipc: sysV msg_init failed: %d\n", err_msg);
> 	shm_init();

This shows the ugliness of the underlying ipc init asymmetry. Specifically,
140d0b2108f (Do 'shm_init_ns()' in an early pure_initcall) was the final
nail in the coffin to fix an exit_shm() race.

While normally we could just initialize the ipc_ids fields statically and
be over with initcall dependencies, your patch will require inits be done
dynamically for the rhashtable_init(). Oh well.

Also, why do you do this?

> -pure_initcall(ipc_ns_init);
> +core_initcall(ipc_ns_init);

Thanks,
Davidlohr