On 2020-04-16 17:38:44 [+0200], Uladzislau Rezki wrote: > > What is the worst thing that can happen if a CPU migration happens > > between raw_cpu_ptr() and spin_lock_irqsave() ? > > > You will just introduce higher rate of lock contention what we would > like to get rid of. The possibility of the migration is minimal. So it is not _always_ happening. > Could you please explain what is broken when you > do like: > > <snip> > local_irq_save(flags); > krcp = this_cpu_ptr(&krc); > spin_lock(&krcp->lock); > <snip> As written in my previous email to Joel (who somehow fell of the Cc list in this part of the thread): |local_irq_save() + spin_lock() is the problem, see | https://www.kernel.org/doc/html/latest/locking/locktypes.html#spinlock-t-and-rwlock-t Sebastian
