linux-kernel - Re: [patch V2 2/7] futex: Hash private futexes per process

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: <20160527165211.GB28561@breakpoint.cc>
Date:	Fri, 27 May 2016 18:52:11 +0200
From:	Sebastian Andrzej Siewior <sebastian@...akpoint.cc>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	LKML <linux-kernel@...r.kernel.org>,
	Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Darren Hart <darren@...art.com>,
	Ingo Molnar <mingo@...nel.org>,
	Michael Kerrisk <mtk.manpages@...glemail.com>,
	Davidlohr Bueso <dave@...olabs.net>, Chris Mason <clm@...com>,
	Carlos O'Donell <carlos@...hat.com>,
	Torvald Riegel <triegel@...hat.com>,
	Eric Dumazet <edumazet@...gle.com>
Subject: Re: [patch V2 2/7] futex: Hash private futexes per process

On 2016-05-19 14:21:48 [+0200], Peter Zijlstra wrote:
> > +static void futex_populate_hash(unsigned int hash_bits)
> > +{
…
> > +	raw_spin_lock(&mm->futex_hash.lock);
> > +	/* We might have raced with another task allocating the hash. */
> > +	if (!mm->futex_hash.hash) {
> > +		mm->futex_hash.hash_bits = hash_bits;
> > +		/*
> > +		 * Ensure that the above is visible before we store
> > +		 * the pointer.
> > +		 */
> > +		smp_wmb(); /* (A0) Pairs with (B) */
> > +		mm->futex_hash.hash = hb;
> 
> 		smp_store_release(&mm->futex_hash.hash, hb); ?

just to be clear: You suggest to use "smp_store_release()" instead
smp_wmb() followed by the assignment?

Sebastian