From: arnd@arndb•de (Arnd Bergmann)
To: linux-arm-kernel@lists•infradead.org
Subject: [RFC] arm: Add for atomic half word exchange
Date: Tue, 19 May 2015 11:51:21 +0200 [thread overview]
Message-ID: <4497461.dn0jdrPFfy@wuerfel> (raw)
In-Reply-To: <1122007906.400701432028368414.JavaMail.weblogic@ep2mlwas07a>
On Tuesday 19 May 2015 09:39:33 Sarbojit Ganguly wrote:
> Since 16 bit half word exchange was not there and MCS based qspinlock by Waiman's xchg_tail() requires an atomic exchange on a half word,
> here is a small modification to __xchg() code.
We have discussed a similar patch before, see
https://lkml.org/lkml/2015/2/25/390
> #if __LINUX_ARM_ARCH__ >= 6
> @@ -50,6 +52,23 @@
> : "r" (x), "r" (ptr)
> : "memory", "cc");
> break;
> + /*
> + * halfword exclusive exchange
> + * This is new implementation as qspinlock
> + * wants 16 bit atomic CAS.
> + */
> + case 2:
> + asm volatile("@ __xchg2\n"
> + "1: ldrexh %0, [%3]\n"
> + " strexh %1, %2, [%3]\n"
> + " teq %1, #0\n"
> + " bne 1b"
> + : "=&r" (ret), "=&r" (tmp)
> + : "r" (x), "r" (ptr)
> + : "memory", "cc");
> + break;
> case 4:
> asm volatile("@ __xchg4\n"
> "1: ldrex %0, [%3]\n"
Please try to find a way to make this compile when CONFIG_CPU_V6
is set.
Arnd
next prev parent reply other threads:[~2015-05-19 9:51 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-05-19 9:39 [RFC] arm: Add for atomic half word exchange Sarbojit Ganguly
2015-05-19 9:51 ` Arnd Bergmann [this message]
-- strict thread matches above, loose matches on Subject: below --
2015-05-19 11:20 Sarbojit Ganguly
2015-05-19 11:42 ` Arnd Bergmann
2015-05-19 12:13 ` Russell King - ARM Linux
2015-05-19 12:43 ` Peter Zijlstra
[not found] <1348896100.440561432098574765.JavaMail.weblogic@ep2mlwas07a>
2015-05-20 6:51 ` Arnd Bergmann
2015-05-20 6:57 ` Peter Zijlstra
[not found] <1357570181.391771433224164775.JavaMail.weblogic@epmlwas06d>
2015-06-02 6:11 ` Raghavendra K T
[not found] <146879519.394951433226103227.JavaMail.weblogic@epmlwas06d>
2015-06-02 10:49 ` Arnd Bergmann
[not found] <274749765.566061433467033693.JavaMail.weblogic@epmlwas07c>
2015-06-05 12:33 ` Arnd Bergmann
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