On Thu, Apr 08, 2021 at 12:56:01PM +0200, Peter Zijlstra wrote: > On Wed, Apr 07, 2021 at 09:24:12PM +0100, Mel Gorman wrote: > > Why local_lock? PREEMPT_RT considers the following sequence to be unsafe > > as documented in Documentation/locking/locktypes.rst > > > > local_irq_disable(); > > raw_spin_lock(&lock); > > Almost, the above is actually OK on RT. The problematic one is: > > local_irq_disable(); > spin_lock(&lock); > > That doesn't work on RT since spin_lock() turns into a PI-mutex which > then obviously explodes if it tries to block with IRQs disabled. > > And it so happens, that's exactly the one at hand. Ok, I completely messed up the leader because it was local_irq_disable() + spin_lock() that I was worried about. Once the series is complete, it is replated with local_lock_irq(&lock_lock) spin_lock(&lock); According to Documentation/locking/locktypes.rst, that should be safe. I'll rephrase the justification. -- Mel Gorman SUSE Labs
