On Thu, Nov 22, 2018 at 11:04:22AM +0900, Sergey Senozhatsky wrote: > Some serial consoles call mod_timer(). So what we could have with the > debug objects enabled was > > mod_timer() > lock_timer_base() > debug_activate() > printk() > call_console_drivers() > foo_console() > mod_timer() > lock_timer_base() << deadlock > > That's one possible scenario. The other one can involve console's > IRQ handler, uart port spinlock, mod_timer, debug objects, printk, > and an eventual deadlock on the uart port spinlock. This one can > be mitigated with printk_safe. But mod_timer() deadlock will require > a different fix. > > So maybe we need to switch debug objects print-outs to _always_ > printk_deferred(). Debug objects can be used in code which cannot > do direct printk() - timekeeping is just one example. No, printk_deferred() is a disease, it needs to be eradicated, not spread around.
