tree e8375c49cbeb8012e55967f325be99b01ab66648
parent 6918bc5c830e890681eabb3c6cb6b8d117a52d14
author Nick Piggin <nickpiggin@yahoo.com.au> 1222771827 +1000
committer Ingo Molnar <mingo@elte.hu> 1222772185 +0200

sched: improve preempt debugging

This patch helped me out with a problem I recently had....

Basically, when the kernel lock is held, then preempt_count underflow does not
get detected until it is released which may be a long time (and arbitrarily,
eg at different points it may be rescheduled). If the bkl is released at
schedule, the resulting output is actually fairly cryptic...

With any other lock that elevates preempt_count, it is illegal to schedule
under it (which would get found pretty quickly). bkl allows scheduling with
preempt_count elevated, which makes underflows hard to debug.

Signed-off-by: Ingo Molnar <mingo@elte.hu>