Re: possible deadlock in console_unlock

[Sergey Senozhatsky]

On (02/18/19 22:07), Yao HongBo wrote:
> >> I have tried GFP_NOWARN, but the problem still exists.
> >> Only print_safe contexts for tty locks can solve the problem.
> >> My test scenario is falt-injection.
> > 
> > Oh, I see. Yes, fault-injection is special.
> > 
> > I suspect that this patch series can be helpful then
> > https://lore.kernel.org/lkml/20181016050428.17966-1-sergey.senozhatsky@xxxxxxxxx/T/#u
> 
> hi, sergey.

Hello,

> I merged this patch series on linux-4.19.18, but it didn't work for the fault-injection cases.

Thanks!

> The failure seems to be the same as before.

OK... So tty_port lock must switch to printk_safe, after all...
I had it in one of the previous versions of the patchset which you
have tested, but people were strictly against new locking rules
in TTY, so I dropped that part. Need to think what we can do here.

BTW,
we are now looking at a completely new printk implementation; which
would not use printk_safe at all:
https://lore.kernel.org/lkml/20190212143003.48446-1-john.ogness@xxxxxxxxxxxxx/T/#u

	-ss