linux-kernel - Re: [PATCH -mm -next] ipc,sem: untangle RCU locking with find_alloc

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Message-ID: <515791A8.7010904@surriel.com>
Date:	Sat, 30 Mar 2013 21:30:16 -0400
From:	Rik van Riel <riel@...riel.com>
To:	Sasha Levin <sasha.levin@...cle.com>
CC:	torvalds@...ux-foundation.org, davidlohr.bueso@...com,
	linux-kernel@...r.kernel.org, akpm@...ux-foundation.org,
	hhuang@...hat.com, jason.low2@...com, walken@...gle.com,
	lwoodman@...hat.com, chegu_vinod@...com,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Subject: Re: [PATCH -mm -next] ipc,sem: untangle RCU locking with find_alloc_undo

On 03/30/2013 09:35 AM, Sasha Levin wrote:

> I'm thinking that the solution is as simple as:

Your patch is absolutely correct.  All it needs now is your
signed-off-by, so Andrew can merge it into -mm :)

Reviewed-by: Rik van Riel <riel@...hat.com>

> diff --git a/ipc/sem.c b/ipc/sem.c
> index 6e109ef..ac36671 100644
> --- a/ipc/sem.c
> +++ b/ipc/sem.c
> @@ -1333,8 +1333,10 @@ static int semctl_main(struct ipc_namespace *ns, int semid, int semnum,
>          /* GETVAL, GETPID, GETNCTN, GETZCNT: fall-through */
>          }
>          err = -EINVAL;
> -       if(semnum < 0 || semnum >= nsems)
> -               goto out_unlock;
> +       if(semnum < 0 || semnum >= nsems) {
> +               rcu_read_unlock();
> +               goto out_wakeup;
> +       }
>
>          sem_lock(sma, NULL, -1);
>          curr = &sma->sem_base[semnum];
>
> But I'm not 100% sure if I don't mess up anything else.

I checked the surrounding code, it all looks fine.

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