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Because it's rwlock_t, which is spinlock :-/ Yeah, sorry > > Here the write side always runs from a process context. > > > > So the write side will block the IRQ which ensures we don't spin > > during read in an IRQ. > > And, does write_lock_irqsave() disable global IRQ or local IRQ only? > > Documentation/locking/locktypes.rst mentions "local_irq_disable()".. It will only disable the local IRQ, since it is a spin type lock an IRQ on another CPU can spin until it is unlocked. The main issue is if this CPU takes an IRQ while the write side is locked and spins, then it will never unlock. Jason