linux-kernel - Re: [PATCH] WorkStruct: Implement generic UP cmpxchg() where an arch doesn't support it

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] [day] [month] [year] [list]

Message-ID: <17007.1165835040@redhat.com>
Date:	Mon, 11 Dec 2006 11:04:00 +0000
From:	David Howells <dhowells@...hat.com>
To:	Russell King <rmk+lkml@....linux.org.uk>
Cc:	Linus Torvalds <torvalds@...l.org>,
	David Howells <dhowells@...hat.com>,
	Christoph Lameter <clameter@....com>,
	Nick Piggin <nickpiggin@...oo.com.au>, akpm@...l.org,
	linux-arm-kernel@...ts.arm.linux.org.uk,
	linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org
Subject: Re: [PATCH] WorkStruct: Implement generic UP cmpxchg() where an arch doesn't support it 

Russell King <rmk+lkml@....linux.org.uk> wrote:

> Yes you can.  Well, you can on ARM at least.  Between the load exclusive
> you can do anything you like until you hit the store exclusive.

How come atomic_set() on arm6 is implemented as:

	static inline void atomic_set(atomic_t *v, int i)
	{
		unsigned long tmp;

		__asm__ __volatile__("@ atomic_set\n"
	"1:	ldrex	%0, [%1]\n"
	"	strex	%0, %2, [%1]\n"
	"	teq	%0, #0\n"
	"	bne	1b"
		: "=&r" (tmp)
		: "r" (&v->counter), "r" (i)
		: "cc");
	}

Why LDREX/STREX and not direct assignment?

David
-
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/