On Fri, 4 Oct 2019 16:41:50 +0200 Michal Hocko <mhocko@xxxxxxxxxx> wrote: > > > This is just insane. The hotplug code is in no way special wrt printk. > > > It is never called from the printk code AFAIK and thus there is no real > > > reason why this particular code should be any special. Not to mention > > > it calls printk indirectly from a code that is shared with other code > > > paths. > > > > Basically, printk() while holding the zone_lock will be problematic as console > > is doing the opposite as it always needs to allocate some memory. Then, it will > > always find some way to form this chain, > > > > console_lock -> * -> zone_lock. > > So this is not as much a hotplug specific problem but zone->lock -> > printk -> alloc chain that is a problem, right? Who is doing an > allocation from this atomic context? I do not see any atomic allocation > in kernel/printk/printk.c. Apparently some console drivers can do memory allocation on the printk() path. This behavior is daft, IMO. Have we identified which ones and looked into fixing them?
