On Tue, 2005-06-28 at 09:42 -0400, Guillaume Autran wrote:

Hi,

I happen to notice a race condition in the mmu_context code for the 8xx 
with very few context (16 MMU contexts) and kernel preemption enable. It 
is hard to reproduce has it shows only when many processes are 
created/destroy and the system is doing a lot of IRQ processing.

In short, one process is trying to steal a context that is in the 
process of being freed (mm->context == NO_CONTEXT) but not completely 
freed (nr_free_contexts == 0).
The steal_context() function does not do anything and the process stays 
in the loop forever.

Anyway, I got a patch that fixes this part. Does not seem to affect 
scheduling latency at all.

Comments are appreciated.

Your patch seems to do a hell lot more than fixing this race ... What
about just calling preempt_disable() in destroy_context() instead ?

Ben.