linux-kernel - Re: [PATCH] printk: Avoid softlockups in console

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:	Tue, 15 Jan 2013 23:37:42 -0800
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Jan Kara <jack@...e.cz>
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	LKML <linux-kernel@...r.kernel.org>, jslaby@...e.cz
Subject: Re: [PATCH] printk: Avoid softlockups in console_unlock()

On Tue, 15 Jan 2013 18:58:34 +0100 Jan Kara <jack@...e.cz> wrote:

> A CPU can be caught in console_unlock() for a long time (tens of seconds are
> reported by our customers) when other CPUs are using printk heavily and serial
> console makes printing slow.  This triggers softlockup warnings because
> interrupts are disabled for the whole time console_unlock() runs (e.g.
> vprintk() calls console_unlock() with interrupts disabled).

It should trigger the NMI watchdog in that case?

> We fix the issue by printing at most 1 KB of messages (unless we are in an
> early boot stage or oops is happening) in one console_unlock() call. The rest
> of the buffer will be printed either by further callers to printk() or by a
> queued work.

Complex.  Did you try just putting a touch_nmi_watchdog() in the loop?
--
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/