linux-kernel - Re: [PATCH 0/2] [RFC] RT: Optionally allow IRQF

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Mon, 08 Oct 2007 10:22:41 -0400
From:	Gregory Haskins <ghaskins@...ell.com>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	Thomas Gleixner <tglx@...utronix.de>, mingo@...e.hu,
	linux-rt-users@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/2] [RFC] RT: Optionally allow IRQF_NODELAY on serial
	console

On Mon, 2007-10-08 at 10:10 -0400, Steven Rostedt wrote:

> This issue has hit me enough times where I've played with a few other
> ideas. I just haven't had the time to finish them. The main problem is if
> the system locks up somewhere we have a lock held that keeps us from
> scheduling. Once that happens in -rt, we are as good as dead. Since you
> can't get much info out without a JTAG or some other mechanism.
> 
> One thought I had was to create a small handler that could read the serial
> and place data into a buffer. This handler would be a IRQ_NODELAY, and it
> would wake up a serial thread to handle the data just like it would for
> normal serial output. But the serial thread would just read from the
> buffer instead of the serial itself.  In the case of a sysrq key coming
> in, the IRQ_NODELAY handler would handle it.
> 

Hi Steve,
  What you describe is exactly what I did.  The IRQF_NODELAY handler
just minimally checks to see if the character is a sysrq related one (or
KDB, if you have the KDB patches applied).  If it is not, it puts the
character into a ring-buffer and wakes a (kthread-based) tasklet to do
the normal serial/tty rx path by processing the ring.

Hope that helps to clarify.

Regards,
-Greg



-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/