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Date: Tue, 3 Feb 2009 00:14:01 -0800
From: Andrew Morton <akpm@linux-foundation.org>
To: Davide Libenzi <davidel@xmailserver.org>
Cc: Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
       Linus Torvalds <torvalds@linux-foundation.org>,
       Alan Cox <alan@lxorguk.ukuu.org.uk>, Ingo Molnar <mingo@elte.hu>,
       David Miller <davem@davemloft.net>
Subject: Re: [patch 2/6] epoll keyed wakeups v2 - introduce new *_poll()
 wakeup macros
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On Sun, 01 Feb 2009 12:04:23 -0800 Davide Libenzi <davidel@xmailserver.org> wrote:

> +#define wake_up_nested_poll(x, m, s)					\
> +do {									\
> +	unsigned long flags;						\
> +									\
> +	spin_lock_irqsave_nested(&(x)->lock, flags, (s));		\
> +	wake_up_locked_poll(x, m);					\
> +	spin_unlock_irqrestore(&(x)->lock, flags);			\
> +} while (0)

I had to go and find the callsite to work out the type of `x' :(

- this macro can be passed the address of any structure which has a
  `spinlock_t lock;' in it, which seems strange.

- It references its first arg three times.

Is there any reason why we can't implement this in C?