linux-kernel - Re: [PATCH v8 06/14] task_isolation: provide strict mode configurable signal

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Date:	Tue, 20 Oct 2015 18:42:52 -0700
From:	Andy Lutomirski <luto@...capital.net>
To:	Chris Metcalf <cmetcalf@...hip.com>
Cc:	Steven Rostedt <rostedt@...dmis.org>,
	Gilad Ben Yossef <giladb@...hip.com>,
	Ingo Molnar <mingo@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Rik van Riel <riel@...hat.com>, Tejun Heo <tj@...nel.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Christoph Lameter <cl@...ux.com>,
	Viresh Kumar <viresh.kumar@...aro.org>,
	Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will.deacon@....com>,
	"linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
	Linux API <linux-api@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v8 06/14] task_isolation: provide strict mode configurable signal

On Tue, Oct 20, 2015 at 6:30 PM, Chris Metcalf <cmetcalf@...hip.com> wrote:
> On 10/20/2015 8:56 PM, Steven Rostedt wrote:
>>
>> On Tue, 20 Oct 2015 16:36:04 -0400
>> Chris Metcalf <cmetcalf@...hip.com> wrote:
>>
>>> Allow userspace to override the default SIGKILL delivered
>>> when a task_isolation process in STRICT mode does a syscall
>>> or otherwise synchronously enters the kernel.
>>>
>> Is this really a good idea? This means that there's no way to terminate
>> a task in this mode, even if it goes astray.
>
>
> It doesn't map SIGKILL to some other signal unconditionally.  It just allows
> the "hey, you broke the STRICT contract and entered the kernel" signal
> to be something besides the default SIGKILL.
>

...which has the odd side effect that sending a non-fatal signal from
another process will cause the strict process to enter the kernel and
receive an extra signal.

I still dislike this thing.  It seems like a debugging feature being
implemented using signals instead of existing APIs.  I *still* don't
see why perf can't be used to accomplish your goal.

--Andy
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