linux-kernel - Re: [PATCH 01/12] netvm: Prevent a stream-specific deadlock

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Message-ID: <1337075234.27694.9.camel@twins>
Date:	Tue, 15 May 2012 11:47:14 +0200
From:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
To:	Mel Gorman <mgorman@...e.de>
Cc:	David Miller <davem@...emloft.net>, akpm@...ux-foundation.org,
	linux-mm@...ck.org, netdev@...r.kernel.org,
	linux-nfs@...r.kernel.org, linux-kernel@...r.kernel.org,
	Trond.Myklebust@...app.com, neilb@...e.de, hch@...radead.org,
	michaelc@...wisc.edu, emunson@...bm.net
Subject: Re: [PATCH 01/12] netvm: Prevent a stream-specific deadlock

On Tue, 2012-05-15 at 10:14 +0100, Mel Gorman wrote:
> @@ -289,6 +289,18 @@ void sk_clear_memalloc(struct sock *sk)
>         sock_reset_flag(sk, SOCK_MEMALLOC);
>         sk->sk_allocation &= ~__GFP_MEMALLOC;
>         static_key_slow_dec(&memalloc_socks);
> +
> +       /*
> +        * SOCK_MEMALLOC is allowed to ignore rmem limits to ensure forward
> +        * progress of swapping. However, if SOCK_MEMALLOC is cleared while
> +        * it has rmem allocations there is a risk that the user of the
> +        * socket cannot make forward progress due to exceeding the rmem
> +        * limits. By rights, sk_clear_memalloc() should only be called
> +        * on sockets being torn down but warn and reset the accounting if
> +        * that assumption breaks.
> +        */
> +       if (WARN_ON(sk->sk_forward_alloc))

WARN_ON_ONCE() perhaps?

> +               sk_mem_reclaim(sk);
>  } 
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