Re: [PATCH] pmac_zilog.c: Fix break handling, add sysrq support

[Benjamin Herrenschmidt <benh@kernel.crashing.org>]

>
> Yes, I agree, that sounds way cleaner than just not lock at all in
> console_write().  But then of course you could still runt into a race
> condition where another thread is already spinning for the lock.  As
> soon as we drop the lock, the other thread would grab it... and when
> console_write() is called via handle_sysrq(), it's already too late,
> isn't it?

Ugh ? handle_sysrq() is called from irq, this should be an irqsafe
lock, another thread on another cpu would just cause us to wait a bit...

> I think this is a generic issue that all serial drivers supporting
> sysrq() face.  Instead of putting some special different solution into
> each driver, I'd say the code from sn_sal_console_write() needs to be
> generalized.
>
> Cc'ing the serial maintainer exactly for this reason.
>
> Russell, what is the preferred solution for this deadlock-prone
> situation?
>
> > I'll have a look, thanks much.
> > Ben.
--
Benjamin Herrenschmidt <benh@kernel.crashing.org>


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