Hi! On Wed, Jun 29, 2005 at 05:25:33PM -0400, Guillaume Autran wrote: > In that case, what happen when a higher priority task steal the context > of the lower priority task after get_mmu_context() but before > set_mmu_context() ? > Then when the lower priority task resumes, its context may no longer be > valid... > Do I get this right ?
Yep... but its OK and expected for the "lower prio task" in question to have its context invalidated: In this case it will call get_mmu_context() again and reserve the next one available before executing. > I'm going to do like this instead of my previous attempt: > > /* Setup new userspace context */ > preempt_disable(); > get_mmu_context(next); > set_context(next->context, next->pgd); > preempt_enable(); > > To make sure we don't loose our context in between. There should be no need - the window for the race is inside get_mmu_context(). ie. It should be safe to preempt after setting "next_mm_context".
