On 02/07/2017 04:48 AM, Ingo Molnar wrote: > * Peter Zijlstra <[email protected]> wrote: > >> On Thu, Feb 02, 2017 at 09:15:26AM -0500, Waiman Long wrote: >>> v2->v3: >>> - Keep the original v1 patches but move patch 3 of v2 in front so >>> as to disable GENERIC_LOCKBREAK when DEBUG_LOCK_ALLOC is on. >>> >>> v1->v2: >>> - Pack lockup and break_lock into a single 4-byte slot so as not >>> to in increase spinlock size when GENERIC_LOCKBREAK is >>> on. Hopefully that will be enough to fix a frame size too large >>> warning in 0-day build. >>> - Add a new patch to disable GENERIC_LOCKBREAK when DEBUG_LOCK_ALLOC >>> is on. >>> >>> The current debug spinlock implementation is a TATAS unfair lock. This >>> can occasionally lead to system lockup with a debug kernel because >>> of the unfairness of the lock rather than inherent locking problem. >>> >>> This patch set changes the debug spinlock implementation to a >>> mostly fair spinlock based on the MCS lock similar to what is done >>> in qspinlock. It also includes a patch that disable GENERIC_LOCKBREAK >>> when DEBUG_LOCK_ALLOC is on. >> >> An alternative is to just delete the thing entirely.. >> >> Ingo, much of what this thing does seems to be superseded by both >> lockdep and a reliable NMI watchdog. Is there still value in >> spinlock_debug? > So there's still early stages when the NMI watchdog is not running, and > spinlock-debug can detect lockups in raw locks that lockdep does not cover, > right? > > But yeah ... it would simplify things all around, so I'm not unsympathetic to > the > idea... > > I've Cc:-ed a few other locking gents. > > Thanks, > > Ingo
I have no problem deleting the debug_spinlock code entirely. I can update the patch to delete the code if you guys think that is the right thing to do. Cheers, Longman
