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Date: Mon, 20 Jan 2014 10:48:01 +0100
From: Gilles Chanteperdrix <gilles.chanteperdrix@xenomai.org>
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Subject: Re: [Xenomai] xnarch_xchg infinite loop
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To: Henri Roosen <henriroosen@gmail.com>
Cc: "Xenomai@xenomai.org" <xenomai@xenomai.org>

On 01/20/2014 09:31 AM, Henri Roosen wrote:
> Hi all,
> 
> We have the problem that (hot-)rebooting our Xenomai system fails every 1
> out of 10 times.
> 
> The system is an ARM iMX6Solo (Cortex-A9) running Xenomai 2.6.2.1 and
> kernel 3.0 (freescale branch).
> 
> When the system hangs at reboot, it is in an infinite loop in the Xenomai
> atomic exchange implementation, with STREX always returning 1:
> 
> __xnarch_xchg
> S:0xC0094B2C : ADD      r3,r6,#0x890
> S:0xC0094B30 : LDREX    r2,[r3]
> S:0xC0094B34 : STREX    r1,r9,[r3]
> S:0xC0094B38 : TEQ      r1,#0
> S:0xC0094B3C : BNE      {pc}-0xc ; 0xc0094b30
> 
> Does anyone know what is causing the STREX to always return 0 and why it
> might get into this state?

Normally, strex fails if "something else" stores data in between ldrex
and strex. Do you have the full stack trace?

-- 
                                                                Gilles.