linux-kernel - Re: [PATCH RFC nohz_full 0/8] Provide infrastructure for full-system idle

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 for Android: free password hash cracker in your pocket

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

Date:	Tue, 25 Jun 2013 15:01:52 -0700
From:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:	Thomas Gleixner <tglx@...utronix.de>
Cc:	linux-kernel@...r.kernel.org, mingo@...e.hu, laijs@...fujitsu.com,
	dipankar@...ibm.com, akpm@...ux-foundation.org,
	mathieu.desnoyers@...icios.com, josh@...htriplett.org,
	niv@...ibm.com, peterz@...radead.org, rostedt@...dmis.org,
	dhowells@...hat.com, edumazet@...gle.com, darren@...art.com,
	fweisbec@...il.com, sbw@....edu
Subject: Re: [PATCH RFC nohz_full 0/8] Provide infrastructure for full-system
 idle

On Tue, Jun 25, 2013 at 11:49:47PM +0200, Thomas Gleixner wrote:
> On Tue, 25 Jun 2013, Paul E. McKenney wrote:
> > Note that this version pays attention to CPUs that have taken an NMI
> > from idle.  It is not clear to me that NMI handlers can safely access
> > the time on a system that is long-term idle.  Unless someone tells me
> > that it is somehow safe to access time from an NMI from idle, I will
> > remove NMI support in the next version.
> 
> NMI cannot access any time related functions independent of NOHZ, long
> term idle or whatever you come up with:
> 
>        write_seqcount_begin(&timekeeper_seq);
> 
> ---> NMI
> 	...
> 	do {
> 	   seq = read_seqcount_begin(&timekeeper_seq);
> 	} while (read_seqcount_retry(&timekeeper_seq, seq));
> 
> Guess how well that works ....

Woo-hoo!!!  I will yank the NMI support on the next version.  Thank
you for the info!

							Thanx, Paul

--
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/