On Fri, 2014-04-25 at 08:28 -0400, Tejun Heo wrote: > On Fri, Apr 25, 2014 at 09:56:10AM +0800, Li Zhong wrote: > > > A nests cpu subsys mutex under s_active of the online node. B nests > > > s_active of the online node under the cpu subsys mutex. What am I > > > missing? > > > > From the above two chain, I think the problem is cpu_subsys_mutex and > > s_active(online), which is the deadlock we are trying to solve in patch > > Yeap, that one was what I was thinking about. > > > #2. I seems to me s_active(release) here doesn't have lock issues? > > And your patch doesn't change the situation for online.
I'm a little confused here... To clarify for this patch(#1): Currently(before patch#2), the s_active(online) and cpu subsys mutex deadlock is solved by lock_device_hotplug_sysfs(). (lockdep warnings are still there, so we want to change the implementation of lock_device_hotplug_sysfs() in patch #2 to take out of s_active_online, instead of device_hotplug_lock, which is grabbed before cpu subsys mutex). But here, for the probe/release, I think we really don't need to use this _sysfs() version. So it is replaced with lock_device_hotplug() directly to avoid two unnecessary conversions of lock_device_hotplug_sysfs(), that otherwise need to be done in patch #2. Thanks, Zhong > Alright, > thanks a lot for the explanation. > -- 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/
