linux-kernel - Re: is printk() safe within a timekeeper

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]

Message-ID: <20140312092125.GA30305@midget.suse.cz>
Date:	Wed, 12 Mar 2014 10:21:25 +0100
From:	Jiri Bohac <jbohac@...e.cz>
To:	John Stultz <john.stultz@...aro.org>
Cc:	Thomas Gleixner <tglx@...utronix.de>, Jiri Bohac <jbohac@...e.cz>,
	linux-kernel@...r.kernel.org,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Subject: Re: is printk() safe within a timekeeper_seq write section?

On Tue, Mar 11, 2014 at 02:54:13PM -0700, John Stultz wrote:
> Ok, so a generic solution is probably not going to be worth it then. My
> thought was that since we do a very limited amount of informational
> printks in the timekeeping code, we can be fairly safe delaying the
> print-out until we drop the locks.
> 
> For timekeeping, its really 4 call sites:
> * invalid inject_sleep_time deltas
> * > 11% clocksource freq adjustments
> * insert leap second
> * delete leap second

I believe these last two were made safe by 
commit ca4523cd (timekeeping: Shorten seq_count region). 

write_seqcount_begin(&timekeeper_seq) is now done after the
accumulate_nsecs_to_secs(tk) from where the printks are called.

Regards,

-- 
Jiri Bohac <jbohac@...e.cz>
SUSE Labs, SUSE CZ

--
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/