On 08/04/2014 06:36 AM, Viresh Kumar wrote: > Sorry for the delay guys, was away :( > >> >> Possible unsafe locking scenario: >> >> CPU0 CPU1 >> ---- ---- >> lock(&policy->rwsem); >> lock(s_active#9); >> lock(&policy->rwsem); >> lock(s_active#9); >> > > Thanks for coming to my rescue Stephen :), I was quite sure I got this > with ondemand > as well..
Yeah, I'm confused by it a bit because I wasn't able to reproduce it. But I've got some pretty clear instructions on how to do it. > > I will be looking very closely at the code now to see what's going wrong. > And btw, does anybody here has the exact understanding of why this > lockdep does happen? I mean what was the real problem for which we The issue is the collision between the setup & teardown of the policy's governor sysfs files. On creation the kernel does: down_write(&policy->rwsem) mutex_lock(kernfs_mutex) <- note this is similar to the "old" sysfs_mutex. The opposite happens on a governor switch, specifically the existing governor's exit, and then we get a lockdep warning. I tried to reproduce with the instructions but was unable to ... ut that was on Friday ;) and I'm going to try again this morning. I've also ping'd some of the engineers here in the office who are working on ARM to get access to a system to do further analysis and testing. I'll ping back later in the day with some results. Sorry I don't have a better answer or solution yet, Viresh. P. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
