From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: Harald Welte <laforge@gnumonks.org>
Cc: rmk+serial@arm.linux.org.uk,
linuxppc-dev list <linuxppc-dev@lists.linuxppc.org>
Subject: Re: [PATCH] pmac_zilog.c: Fix break handling, add sysrq support
Date: Tue, 10 Aug 2004 10:24:17 +1000 [thread overview]
Message-ID: <1092097456.14100.54.camel@gaston> (raw)
In-Reply-To: <20040808112147.GA31341@obroa-skai.de.gnumonks.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>
** Sent via the linuxppc-dev mail list. See http://lists.linuxppc.org/
prev parent reply other threads:[~2004-08-10 0:24 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-08-06 10:43 [PATCH] pmac_zilog.c: Fix break handling, add sysrq support Harald Welte
2004-08-06 10:44 ` Benjamin Herrenschmidt
2004-08-08 11:21 ` Harald Welte
2004-08-10 0:24 ` Benjamin Herrenschmidt [this message]
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