linux-kernel - Re: [PATCH v2 26/31] arm64: Miscellaneous library functions

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, 16 Aug 2012 15:11:53 +0100
From:	Catalin Marinas <catalin.marinas@....com>
To:	Arnd Bergmann <arnd@...db.de>
Cc:	Will Deacon <Will.Deacon@....com>,
	"linux-arch@...r.kernel.org" <linux-arch@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Marc Zyngier <Marc.Zyngier@....com>
Subject: Re: [PATCH v2 26/31] arm64: Miscellaneous library functions

On Thu, Aug 16, 2012 at 02:00:32PM +0100, Arnd Bergmann wrote:
> On Thursday 16 August 2012, Will Deacon wrote:
> > > > +
> > > > +#include <linux/kernel.h>
> > > > +#include <linux/spinlock.h>
> > > > +#include <linux/atomic.h>
> > > > +
> > > > +#ifdef CONFIG_SMP
> > > > +arch_spinlock_t __atomic_hash[ATOMIC_HASH_SIZE] __lock_aligned = {
> > > > +       [0 ... (ATOMIC_HASH_SIZE-1)]  = __ARCH_SPIN_LOCK_UNLOCKED
> > > > +};
> > > > +#endif
> > > 
> > > What?
> > > 
> > > I suppose this is a leftover from an earlier version using the
> > > generic bitops, right?
> > 
> > We currently use the generic atomic bitops (asm-generic/bitops/atomic.h)
> > which contains:
> > 
> > #  define ATOMIC_HASH(a) (&(__atomic_hash[ (((unsigned long) a)/L1_CACHE_BYTES) & (ATOMIC_HASH_SIZE-1) ]))
> > 
> > so we have to provide a definition for the array. We have additional patches
> > containing optimised assembly implementations of the atomic bitops which we
> > will push later, once we've got some hardware to benchmark with.
> > 
> 
> Ah, I was confusing this with the asm/atomic.h stuff, for which you already
> provide an optimized version.
> 
> The generic atomic bitops are really horrible in performance and I would
> expect that there is just one obvious way to implement bitops using ldaxr/stlxr,
> so I recommend just doing that even if you have no hardware for benchmarking.

As Will said, we have the code already but I dropped it from the initial
set patches to be reviewed to keep them simpler. They will be added
later.

-- 
Catalin
--
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/