Hi Philp, Yes. I am agree with you. Just drop is better to support recursive lock. I will send a new patch later. Regards Feng On Fri, Aug 19, 2016 at 12:48 AM, Philp Prindeville <philipp@xxxxxxxxxxxxxxxxxxxxx> wrote: > > > On 08/18/2016 09:05 AM, Feng Gao wrote: >> >> On Thu, Aug 18, 2016 at 10:11 PM, Philp Prindeville >> <philipp@xxxxxxxxxxxxxxxxxxxxx> wrote: >>> >>> >Feng, >>> > >>> >If the CPU can already be holding the lock, that implies re-entrancy. >>> >What's to stop the first flow of code which acquired the lock from >>> > releasing >>> >it again before the 2nd flow is done? Is the 2nd flow running at a >>> > higher >>> >priority or with interrupts disabled? >> >> There is no preemption happened. It is caused by wrong route policy by >> l2tp. >> For example, the cpu0 get the spinlock of channel1, then the channel1 >> is selected again after route. As a result, cpu0 tries to get the same >> spinlock again. >> >> The call flow is like this. >> ppp_write->ppp_channel_push->start_xmit->select inappropriate route >> .... -> dev_hard_start_xmit->ppp_start_xmit->ppp_xmit_process-> >> ppp_push. Now ppp_push tries to get the same spinlock which is held >> in ppp_channel_push. >> >> Regards >> Feng >> > > If we're detecting (through the fact that the lock has already been > acquired) that the wrong route is being applied, why don't we just punt the > packet instead? > > -Philip > -- To unsubscribe from this list: send the line "unsubscribe linux-ppp" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
