linux-kernel - Re: [PATCH 1/2] ipc,shm: move BUG_ON check into shm

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Message-ID: <1433444334.2320.30.camel@stgolabs.net>
Date:	Thu, 04 Jun 2015 11:58:54 -0700
From:	Davidlohr Bueso <dave@...olabs.net>
To:	Manfred Spraul <manfred@...orfullife.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] ipc,shm: move BUG_ON check into shm_lock

On Thu, 2015-06-04 at 20:35 +0200, Manfred Spraul wrote:
> Hi Davidlohr,
> 
> On 05/30/2015 02:03 AM, Davidlohr Bueso wrote:
> > Upon every shm_lock call, we BUG_ON if an error was returned,
> > indicating racing either in idr or in RMID. Move this logic
> > into the locking.
> >
> > Signed-off-by: Davidlohr Bueso <dbueso@...e.de>
> > ---
> >   ipc/shm.c | 11 +++++++----
> >   1 file changed, 7 insertions(+), 4 deletions(-)
> >
> > diff --git a/ipc/shm.c b/ipc/shm.c
> > index 6d76707..3152dea 100644
> > --- a/ipc/shm.c
> > +++ b/ipc/shm.c
> > @@ -155,8 +155,14 @@ static inline struct shmid_kernel *shm_lock(struct ipc_namespace *ns, int id)
> >   {
> >   	struct kern_ipc_perm *ipcp = ipc_lock(&shm_ids(ns), id);
> >   
> > -	if (IS_ERR(ipcp))
> > +	if (IS_ERR(ipcp)) {
> > +		/*
> > +		 * We raced in the idr lookup or with RMID,
> > +		 * either way, the ID is busted.
> The comment is wrong:
> "We raced in the idr lookup or with shm_destroy()"

Yes, you are absolutely right. Thanks for the review.

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