On 02/23/2015 11:37 AM, Steven Rostedt wrote: > > OK, I believe I understand the issue. Perhaps it would be much better > to create a fake task per CPU that we use when grabbing locks in > interrupt mode. And make these have a priority of 0 (highest), since > they can not be preempted, they do have such a priority. > > Then in the fast trylock and unlock code, we can add: > > struct task_struct *curr = current; > > if (unlikely(in_irq())) > curr = this_cpu_read(irq_task); > > This way the priority inheritance will stop when it hits this task (no > need to boost a task of highest priority), and we can leave that code > alone. > Thanks again for the comments and suggestion. Yes, creating a per cpu fake task was one of the alternative considered. I believe one of the reasons I did not purse is the amount of extra storage it requires (sizeof(struct task_struct) * number of cpus. Though the changes may not be as intrusive as the one I sent, some are still required, mainly with current (one in particular came to mind is in wakeup_next-watier()). If I'm not mistaken, another reason could also be due to the rate of the timer interrupt, in the case that the mutex is highly contested IH could stall the non-real-time requester for a long time, even to the point of the cpu is perceived as hung. Anyway, I'll retry the fake task approach a try and report back if there is any issue. Thanks, Mak. > -- Steve > -- > To unsubscribe from this list: send the line "unsubscribe linux-rt-users" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html > -- To unsubscribe from this list: send the line "unsubscribe linux-rt-users" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
