On (03/12/19 16:15), John Ogness wrote:
> > I suggest the following way forward (separate patchsets):
> >
> > 1. Replace log buffer (least controversial thing)
>
> Yes. I will post a series that only implements the ringbuffer using your
> simplified API. That will be enough to remove printk_safe and actually
> does most of the work of updating devkmsg, kmsg_dump, and syslog.
This may _not_ be enough to remove printk_safe. One of the reasons
printk_safe "condom" came into existence was console_sem (which
is a bit too important to ignore it):
printk()
console_trylock()
console_unlock()
up()
raw_spin_lock_irqsave(&sem->lock, flags)
__up()
wake_up_process()
WARN/etc
printk()
console_trylock()
down_trylock()
raw_spin_lock_irqsave(&sem->lock, flags) << deadlock
Back then we were looking at
printk->console_sem->lock->printk->console_sem->lock
deadlock report from LG, if I'm not mistaken.
-ss
