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Date: Tue, 5 Jan 2016 13:06:15 +0800
From: "Wangnan (F)" <wangnan0@huawei.com>
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To: Will Deacon <will.deacon@arm.com>
CC: <takahiro.akashi@linaro.org>, <guohanjun@huawei.com>,
        <linux-arm-kernel@lists.infradead.org>, <linux-kernel@vger.kernel.org>,
        <pi3orama@163.com>, Fengguang Wu <fengguang.wu@intel.com>,
        Jiri Olsa <jolsa@kernel.org>
Subject: Re: [PATCH v2] arm64: Store breakpoint single step state into pstate
References: <1450860731-194418-1-git-send-email-wangnan0@huawei.com> <1450921362-198371-1-git-send-email-wangnan0@huawei.com> <20160104165535.GI1616@arm.com>
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Hi Will,

On 2016/1/5 0:55, Will Deacon wrote:
> Hello,
>
> On Thu, Dec 24, 2015 at 01:42:42AM +0000, Wang Nan wrote:

[SNIP]

> The problem seems to be that we take the debug exception before the
> breakpointed instruction has been executed and call perf_bp_event at
> that moment, so when we single-step the faulting instruction we actually
> step into the SIGIO handler and end up getting stuck.
>
> Your fix doesn't really address this afaict, in that you don't (can't?)
> handle:
>
>    * A longjmp out of a signal handler
>    * A watchpoint and a breakpoint that fire on the same instruction
>    * User-controlled single-step from a signal handler that enables a
>      breakpoint explicitly
>    * Nested signals

Please have a look at [1], which I improve test__bp_signal() to
check bullet 2 and 4 you mentioned above. Seems my fix is correct.

[1] 
http://lkml.kernel.org/g/1451969880-14877-1-git-send-email-wangnan0@huawei.com

Thank you.