linux-kernel - cpu4096 + smp

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Message-ID: <488F2A65.2090405@gmail.com>
Date:	Tue, 29 Jul 2008 16:34:13 +0200
From:	Jiri Slaby <jirislaby@...il.com>
To:	Ingo Molnar <mingo@...e.hu>
CC:	Mike Travis <travis@....com>,
	Linux kernel mailing list <linux-kernel@...r.kernel.org>
Subject: cpu4096 + smp_affinity breakage

Hi,

I see cpu4096 branches in -tip. Do you know about /proc/irq/*/*smp_affinity 
(irq_affinity_read_proc, default_affinity_read) breakage with NR_CPUS=4096? 
Reading by `cat' from those files fails due to bitmap sent out is about 1150 
bytes, but cat provides only 1024B sized buffer. Can you think about any fix 
for this?

Using file offset and utilize only portion of that buffer returned to the 
userspace will break atomicity I guess (does this matter?). If we get a 
snapshot, it would get old if some reader breaks up. And if we use 
per-reader buffer, we will be unable to free it. Any ideas?

I think the same problem is for not-at-once-writes.
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