On Sat, Nov 5, 2011 at 8:50 PM, Lin Ming <ming.m.lin@xxxxxxxxx> wrote: > On Fri, 2011-11-04 at 13:53 +0800, Rakib Mullick wrote: >> On Thu, Nov 3, 2011 at 11:40 PM, Srivatsa S. Bhat >> <srivatsa.bhat@xxxxxxxxxxxxxxxxxx> wrote: >> > Hi, >> > >> > On 11/03/2011 05:32 PM, Lin Ming wrote: >> >> On Thu, 2011-11-03 at 18:48 +0800, Rakib Mullick wrote: >> >>> Calling pm-suspend might trigger a recursive lock in it's code path. In function acpi_hw_clear_acpi_status, >> >> >> >> As I replied at https://lkml.org/lkml/2011/9/22/6, I still don't think >> >> there is a recursive lock. >> >> >> > >> > At first look, it definitely doesn't look like a recursive lock, as Lin said. >> > But, quoting Documentation/lockdep-design.txt: >> > >> > "Multi-lock dependency rules: >> > ---------------------------- >> > >> > The same lock-class must not be acquired twice, because this could lead >> > to lock recursion deadlocks." >> > >> > So, Rakib, do the 2 locks belong to the same lock-class? If yes, then I think >> > that is the reason for the lockdep splat. Could you show the lockdep warning? >> > >> Yes, same lock-class. And as per "Multi-lock dependency rules:", it >> leads to lock recursion deadlocks. >> Lockdep warning attached. >> >> > By the way, another way to look at this patch is as an optimization.. >> > i.e., if acpi_gbl_hardware_lock doesn't need to be held to call >> > acpi_ev_walk_gpe_list(), then we can move from the coarse-grained locking >> > to finer-grained locking by releasing it earlier, as you did in your patch. >> > [Note that you will have to update the goto label also, i.e., rename it as >> > 'exit' or something like that] >> > >> I can do it, thanks for suggestions. But, what does Lin thinks? Lin >> are you okay? > > I'm OK. > Thanks. Then, I'll come up with a follow up patch includes the suggestion from Srivatsa. > We need to figure out why the dead lock happens. I think its pretty clear from the lockdep warning, the reason of the possible (since not happened with mainline kernel) dead lock. > Could you also paste the patch which trigger this dead lock? > It's basically a modification of kernel scheduler, it does load distribution differently. Since it's different approach and needs to introduce properly. I wish I'll show it some day, if I can make some fair improvement. Hope you understand. Thanks, Rakib -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
