> From: David Hildenbrand [mailto:dahi@xxxxxxxxxxxxxxxxxx] > > > From: David Hildenbrand > > > ... > > > > Although it might not be optimal, but keeping a separate counter for > > > > pagefault_disable() as part of the preemption counter seems to be the only > > > > doable thing right now. I am not sure if a completely separated counter is even > > > > possible, increasing the size of thread_info. > > > > > > What about adding (say) 0x10000 for the more restrictive test? > > > > > > David > > > > > > > You mean as part of the preempt counter? > > > > The current layout (on my branch) is > > > > * PREEMPT_MASK: 0x000000ff > > * SOFTIRQ_MASK: 0x0000ff00 > > * HARDIRQ_MASK: 0x000f0000 > > * NMI_MASK: 0x00100000 > > * PREEMPT_ACTIVE: 0x00200000 > > > > I would have added > > * PAGEFAULT_MASK: 0x03C00000 > > I'm not sure where you'd need to add the bits. > > I think the above works because disabling 'HARDIRQ' implicitly > disables 'SOFTIRQ' and 'PREEMPT' (etc), so if 256+ threads > disable PREEMPT everything still works. AFAIK 256+ levels of preempt will break the system :) Therefore with CONFIG_DEBUG_PREEMPT we verify that we don't have any over/underflows. But such bugs can only be found with CONFIG_DEBUG_PREEMPT enabled. > > So if disabling pagefaults implies that pre-emption is disabled > (but SOFTIRQ is still allowed) then you need to insert your bit(s) > between 0xff00 and 0x00ff. > OTOH if disabling pre-emption implies that pagefaults are disabled > then you'd need to use the lsb and change all the above values. > > Which makes me think that 'PREEMPT_ACTIVE' isn't right at all. > Two threads disabling NMIs (or 32 disabling HARDIRQ) won't DTRT. With threads you mean levels? This is a per thread information. > > OTOH I'm only guessing at how this is used. > > David > > > -- To unsubscribe from this list: send the line "unsubscribe linux-arch" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
