On Tue, Apr 17, 2012 at 09:35:49PM -0600, Moore, Eric wrote: > Jan Schmidt suggested using raw_smp_processor_id() back in February, see this: http://marc.info/?t=132974687100003&r=1&w=2 > > Alex Shi recently suggested using preempt_disable() and preempt_enable() to solve the same issue, see this: http://marc.info/?t=133274303900003&r=1&w=2 > > I believe the stack traces are there in both email discussion, they occur when CONFIG_DEBUG_PREEMPT is enabled. > > I would rather go with the solution giving the best performance. James Bottomley is there on the discussion with Jan Schmidt, he suggested using get_cpu() and put_cpu(). I use get_cpu() / put_cpu() in the NVMe driver in similar circumstances. It's not noticable in the profiles :-) Where my usage differs from the patch for mpt2sas is that I hold a reference to the CPU over the submission. This works out well for me because I have per-CPU state. Might be worth considering for your driver ... -- Matthew Wilcox Intel Open Source Technology Centre "Bill, look, we understand that you're interested in selling us this operating system, but compare it to ours. We can't possibly take such a retrograde step." -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
