On Wed, Nov 10, 2021 at 12:20:05PM +0100, Peter Zijlstra wrote: > On Wed, Nov 10, 2021 at 11:50:38AM +0100, Petr Mladek wrote: > > On Tue 2021-11-09 12:06:48, Sultan Alsawaf wrote: > > > Hi, > > > > > > I encountered a printk deadlock on 5.13 which appears to still affect the latest > > > kernel. The deadlock occurs due to printk being used while having the current > > > CPU's runqueue locked, and the underlying framebuffer console attempting to lock > > > the same runqueue when printk tries to flush the log buffer. > > > > > > I'm not sure what the *correct* solution is here (don't use printk while having > > > a runqueue locked? don't use schedule_work() from the fbcon path? tell printk > > > to use one of its lock-less backends?), so I've cc'd all the relevant folks. > > > > At the moment, printk_deferred() could be used here. It defers the > > console handling via irq_work(). > > I think I've rejected that patch at least twice now :-) John's printk > stuff will really land real soon now, right. Yeah whacking all affected prinkt callers just because of fbcon does not sound like a good idea to me either. -Daniel -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch
