linux-kernel - Re: [PATCH 2/6] mm: mark all calls into the vmalloc subsystem as potentially sleeping

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Date:   Wed, 19 Oct 2016 20:43:33 +0100
From:   Chris Wilson <chris@...is-wilson.co.uk>
To:     Christoph Hellwig <hch@....de>
Cc:     Andy Lutomirski <luto@...capital.net>,
        Andrew Morton <akpm@...ux-foundation.org>, joelaf@...gle.com,
        jszhang@...vell.com, joaodias@...gle.com,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        linux-rt-users@...r.kernel.org,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/6] mm: mark all calls into the vmalloc subsystem as
 potentially sleeping

On Wed, Oct 19, 2016 at 06:31:12PM +0200, Christoph Hellwig wrote:
> On Wed, Oct 19, 2016 at 08:34:40AM -0700, Andy Lutomirski wrote:
> > 
> > It would be quite awkward for a task stack to get freed from a
> > sleepable context, because the obvious sleepable context is the task
> > itself, and it still needs its stack.  This was true even in the old
> > regime when task stacks were freed from RCU context.
> > 
> > But vfree has a magic automatic deferral mechanism.  Couldn't you make
> > the non-deferred case might_sleep()?
> 
> But it's only magic from interrupt context..
> 
> Chris, does this patch make virtually mapped stack work for you again?

So far, so good. No warns from anyone else.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre