Hi! On 23:53 Sat 08 Oct , Dave Hylands wrote: > Hi Michi, > > On Sat, Oct 8, 2011 at 11:29 PM, Michael Blizek > <michi1@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx> wrote: ... > > Disabling interrupts actually disables preemption as well. Preemption is > > triggered by a timer interrupt, which cannot arrive in this case. Spinlocks > > can be aquired both by disabling interrupts (spin_lock_irqsave) or by > > disabling preemption (spin_lock_bh). However, you cannot use spin_lock_bh if > > the same spin_lock is aquired in an interrupt handler. spin_lock_bh allows > > interrupt handlers to be invoked while you are still in the critical section. > > If the interrupt handler is processed on the same CPU as the critical section, > > you are stuck in a deadlock. > > Disabling interrupts DOES NOT disable preemption on an SMP machine. It > only disables preemption on the core that interrupts are disabled on. AFAIK there is no "global" preemption disable in linux. This operation would be very slow. There is stop_machine for stuff like module loading, but I guess this is not what you mean. spin_lock_bh also disables preemption only on the local cpu. -Michi -- programing a layer 3+4 network protocol for mesh networks see http://michaelblizek.twilightparadox.com _______________________________________________ Kernelnewbies mailing list Kernelnewbies@xxxxxxxxxxxxxxxxx http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
