linux-kernel - Re: [PATCH v2] arm64: Store breakpoint single step state into pstate

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Message-ID: <568B4F47.5080307@huawei.com>
Date:	Tue, 5 Jan 2016 13:06:15 +0800
From:	"Wangnan (F)" <wangnan0@...wei.com>
To:	Will Deacon <will.deacon@....com>
CC:	<takahiro.akashi@...aro.org>, <guohanjun@...wei.com>,
	<linux-arm-kernel@...ts.infradead.org>,
	<linux-kernel@...r.kernel.org>, <pi3orama@....com>,
	Fengguang Wu <fengguang.wu@...el.com>,
	Jiri Olsa <jolsa@...nel.org>
Subject: Re: [PATCH v2] arm64: Store breakpoint single step state into pstate

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.


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