Message-ID: <1433895192.3165.67.camel@stgolabs.net>
Subject: Re: [PATCH 1/5] ipc,shm: move BUG_ON check into shm_lock
From: Davidlohr Bueso <dave@stgolabs.net>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Manfred Spraul <manfred@colorfullife.com>, linux-kernel@vger.kernel.org,
        linux-mm@kvack.org
Date: Tue, 09 Jun 2015 17:13:12 -0700
In-Reply-To: <20150609152838.94774d7feafef3f7e6ccbd74@linux-foundation.org>
References: <1433597880-8571-1-git-send-email-dave@stgolabs.net>
	 <1433597880-8571-2-git-send-email-dave@stgolabs.net>
	 <20150609152838.94774d7feafef3f7e6ccbd74@linux-foundation.org>
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On Tue, 2015-06-09 at 15:28 -0700, Andrew Morton wrote:
> --- a/ipc/shm.c~ipcshm-move-bug_on-check-into-shm_lock-fix
> +++ a/ipc/shm.c
> @@ -155,14 +155,11 @@ static inline struct shmid_kernel *shm_l
>  {
>  	struct kern_ipc_perm *ipcp = ipc_lock(&shm_ids(ns), id);
>  
> -	if (IS_ERR(ipcp)) {
> -		/*
> -		 * We raced in the idr lookup or with shm_destroy(),
> -		 * either way, the ID is busted.
> -		 */
> -		BUG();
> -		return (struct shmid_kernel *)ipcp;
> -	}
> +	/*
> +	 * We raced in the idr lookup or with shm_destroy().  Either way, the
> +	 * ID is busted.
> +	 */
> +	BUG_ON(IS_ERR(ipcp));
>  
>  	return container_of(ipcp, struct shmid_kernel, shm_perm);
>  }
> 
> One benefit of the code you sent is that the unreachable `return' will
> prevent a compile warning when CONFIG_BUG=n, but CONFIG_BUG=n is silly
> and I never worry about it.

I took a closer look and the above looks Ok, and I don't care either way
about CONFIG_BUG=n.

Thanks,
Davidlohr

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