linux-kernel - Re: [PATCH] socfpga_a10: reset CPU1 in socfpga_cpu

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Message-ID: <20170515095513.GS22219@n2100.armlinux.org.uk>
Date:   Mon, 15 May 2017 10:55:14 +0100
From:   Russell King - ARM Linux <linux@...linux.org.uk>
To:     yanjiang.jin@...driver.com
Cc:     mark.rutland@....com, dinguyen@...nel.org,
        dinguyen@...nsource.altera.com, jinyanjiang@...il.com,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] socfpga_a10: reset CPU1 in socfpga_cpu_kill()

On Mon, May 15, 2017 at 05:13:36PM +0800, yanjiang.jin@...driver.com wrote:
> From: Yanjiang Jin <yanjiang.jin@...driver.com>
> 
> socfpga_cpu_die() just puts CPU in WFI, not actually off. So that Kexec's
> second kernel goes wrong since the kerenl text gets ovewritten.
> Now reset CPU1 in cpu_kill() to avoid this error.
> Also add flush_cache_all() to prevent data from being lost in cpu_die().

You should not need this, as the common code does the cache flushing
for you.

It's rather unsafe too - you are completely unsynchronised between the
CPU executing in cpu_die() and the CPU executing cpu_kill() - it's
quite possible for the code in cpu_kill() to take effect when you're
part-way through the flush_cache_all().

-- 
RMK's Patch system: http://www.armlinux.org.uk/developer/patches/
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