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Date: Tue, 27 Jan 2009 14:10:42 +0100
From: Jan Kiszka <jan.kiszka@domain.hid>
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Subject: Re: [Xenomai-core] Pending patches
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Philippe Gerum wrote:
> We should indeed postpone this just in case the upper layer indexes the extra
> state on the minor value. We can also simplify a few things doing so.
> 
> --- ksrc/nucleus/pipe.c	(revision 4565)
> +++ ksrc/nucleus/pipe.c	(working copy)
> @@ -77,11 +77,9 @@
> 
>  static inline void xnpipe_minor_free(int minor)
>  {
> -	if (minor < 0 || minor >= XNPIPE_NDEVS)
> -		return;
> -
> -	__clrbits(xnpipe_bitmap[minor / BITS_PER_LONG],
> -		  1UL << (minor % BITS_PER_LONG));
> +	/* May be called with nklock free. */
> +	clrbits(xnpipe_bitmap[minor / BITS_PER_LONG],
> +		1UL << (minor % BITS_PER_LONG));

Bad news: This doesn't fly as is. All modifying operations on
xnpipe_bitmap must be atomic and xnpipe_bitmap has to be
xnarch_atomic_t. But then find_first_zero_bit breaks. Is there some
version for atomic arrays? I guess we have to open-code this, at least
down to word-level...

Jan

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Siemens AG, Corporate Technology, CT SE 2
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