linux-kernel - Re: [PATCH] mm:Avoid soft lockup due to possible attempt of double locking object's lock in __delete

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Message-ID: <33981.1472677706@turing-police.cc.vt.edu>
Date:   Wed, 31 Aug 2016 17:08:26 -0400
From:   Valdis.Kletnieks@...edu
To:     Catalin Marinas <catalin.marinas@....com>
Cc:     Nicholas Krause <xerofoify@...il.com>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm:Avoid soft lockup due to possible attempt of double locking object's lock in __delete_object

On Wed, 31 Aug 2016 08:54:21 +0100, Catalin Marinas said:
> On Tue, Aug 30, 2016 at 02:35:12PM -0400, Nicholas Krause wrote:
> > This fixes a issue in the current locking logic of the function,
> > __delete_object where we are trying to attempt to lock the passed
> > object structure's spinlock again after being previously held
> > elsewhere by the kmemleak code. Fix this by instead of assuming
> > we are the only one contending for the object's lock their are
> > possible other users and create two branches, one where we get
> > the lock when calling spin_trylock_irqsave on the object's lock
> > and the other when the lock is held else where by kmemleak.
>
> Have you actually got a deadlock that requires this fix?

Almost certainly not, but that's never stopped Nicholas before.  He's a well-known
submitter of bad patches, usually totally incorrect, not even compile tested.

He's infamous enough that he's not allowed to post to any list hosted at vger.

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