cpu4096 + smp_affinity breakage

From: Jiri Slaby
Date: Tue Jul 29 2008 - 10:34:26 EST


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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