linux-kernel - Re: Query regarding synchronize_sched_expedited and resched

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:   Thu, 21 Sep 2017 15:55:46 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     Neeraj Upadhyay <neeraju@...eaurora.org>,
        paulmck@...ux.vnet.ibm.com, josh@...htriplett.org,
        mathieu.desnoyers@...icios.com, jiangshanlai@...il.com,
        linux-kernel@...r.kernel.org, sramana@...eaurora.org,
        prsood@...eaurora.org, pkondeti@...eaurora.org,
        markivx@...eaurora.org
Subject: Re: Query regarding synchronize_sched_expedited and resched_cpu

On Mon, Sep 18, 2017 at 11:11:05AM -0400, Steven Rostedt wrote:
> On Sun, 17 Sep 2017 11:37:06 +0530
> Neeraj Upadhyay <neeraju@...eaurora.org> wrote:
> 
> > Hi Paul, how about replacing raw_spin_trylock_irqsave with
> > raw_spin_lock_irqsave in resched_cpu()? Are there any paths
> > in RCU code, which depend on trylock check/spinlock recursion?
> 
> It looks to me that resched_cpu() was added for nohz full sched
> balancing, but is not longer used by that. The only user is currently
> RCU. Perhaps we should change that from a trylock to a lock.

No, regular NOHZ balancing. NOHZ FULL wasn't conceived back then.

  46cb4b7c88fa ("sched: dynticks idle load balancing")

And yeah, its no longer used for that.

And given RCU is the only user of that thing, I suppose we can indeed
change it to a full lock.