Thanks On Tue, Jun 3, 2014 at 4:00 PM, Thomas Gleixner <tglx@xxxxxxxxxxxxx> wrote: > 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
