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

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Date:   Tue, 06 Sep 2016 20:45:19 -0400
From:   Rik van Riel <riel@...hat.com>
To:     nick <xerofoify@...il.com>,
        Catalin Marinas <catalin.marinas@....com>
Cc:     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, 2016-08-31 at 09:24 -0400, nick wrote:
> 
> On 2016-08-31 03:54 AM, Catalin Marinas wrote:
> > 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?
> > 
> Yes I have got a deadlock that this does fix.

Why don't you share the backtrace with us?

Claiming you have a deadlock, but not sharing
it on the list means nobody can see what the
problem is you are trying to address.

It would be good if every email with a patch
that you post starts with an actual detailed
problem description.

Can you do that?

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