On Tue, 3 Jun 2014, Grant Likely wrote: > On Wed, Jun 12, 2013 at 8:49 AM, Thomas Gleixner <tglx@xxxxxxxxxxxxx> wrote: > > On Tue, 11 Jun 2013, Scott Wood wrote: > > > >> I get the following lockdump output on p2020rdb using > >> v3.10-rc5-43-g34376a5. While it's not particularly polite for the > >> esdhc driver to be calling OF functions while holding another lock which > >> can be acquired from interrupt context, why is devtree_lock usually > >> acquired in an irqsafe manner but sometimes not? > >> > >> Both types of usage were added by the same commit: > >> > >> commit d6d3c4e656513dcea61ce900f0ecb9ca820ee7cd > >> Author: Thomas Gleixner <tglx@xxxxxxxxxxxxx> > >> Date: Wed Feb 6 15:30:56 2013 -0500 > >> > >> OF: convert devtree lock from rw_lock to raw spinlock > >> > >> Stephen, you asked about this here: > >> http://lkml.indiana.edu/hypermail/linux/kernel/1302.1/01383.html > >> > >> Did you ever get an answer? > > > > https://patchwork.kernel.org/patch/2470731/ > > > >> I'm also curious why devtree_lock was made raw to begin with... > >> Iterating over a device tree doesn't seem like something you'd want to > >> trust to be low-latency. > > > > The reason is that it's taken in low level cpu bringup code and I did > > not find a different solution. :( > > Hey, Thomas, > > Do you remember where the offending code is? I'm looking at completely > refactoring FDT locking so I'd like to take a crack and solving the > cpu bringup problem. Hmm, can't remember. All I found is where it got introduced: https://lkml.org/lkml/2007/11/9/114 without comments of course :) Ask someone with a pseries to grab RT and make the lock non raw. Enable debugging (mightsleep, lockdep ...) Boot with maxcpus=1 and then online cores from user space. Splat should come right away. I remember that I saw some of them in a pastebin. Thanks, tglx -- To unsubscribe from this list: send the line "unsubscribe linux-mmc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
