Re: CONFIG_DEBUG_PREEMPT (was: [PATCH 04/04] Cpuset: skip rcu check ...)

[Greg Edwards]

On Mon, Dec 19, 2005 at 08:04:01AM -0800, Paul Jackson wrote:
| Greg - CONFIG_DEBUG_PREEMPT adds a couple of pages of assembly code 
| due to various BUG checks beneath rcu_read_lock() on some hot code
| paths (which is where rcu is most popular).  See the two calls
| add_preempt_count() and sub_preempt_count() in kernel/sched.c.
| 
| Was this intentional to enable CONFIG_DEBUG_PREEMPT in sn2_defconfig?

It wasn't intentional at the time.  I believe it was pulled in
automatically when we refreshed since we had CONFIG_PREEMPT on.  That
said, it has proven itself useful in turning up some bugs.

Greg
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