linux-kernel - Re: [RFC PATCH 15/18] ring_buffer: Allow to exit the ring buffer benchmark immediately

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Message-ID: <20150608134417.3fb7a811@gandalf.local.home>
Date:	Mon, 8 Jun 2015 13:44:17 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Petr Mladek <pmladek@...e.cz>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Oleg Nesterov <oleg@...hat.com>, Tejun Heo <tj@...nel.org>,
	Ingo Molnar <mingo@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Richard Weinberger <richard@....at>,
	David Woodhouse <dwmw2@...radead.org>,
	linux-mtd@...ts.infradead.org,
	Trond Myklebust <trond.myklebust@...marydata.com>,
	Anna Schumaker <anna.schumaker@...app.com>,
	linux-nfs@...r.kernel.org, Chris Mason <clm@...com>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Jiri Kosina <jkosina@...e.cz>, Borislav Petkov <bp@...e.de>,
	Michal Hocko <mhocko@...e.cz>, live-patching@...r.kernel.org,
	linux-api@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH 15/18] ring_buffer: Allow to exit the ring buffer
 benchmark immediately

On Fri,  5 Jun 2015 17:01:14 +0200
Petr Mladek <pmladek@...e.cz> wrote:

> It takes a while until the ring_buffer_benchmark module is removed
> when the ring buffer hammer is running. It is because it takes
> few seconds and kthread_should_terminate() is not being checked.
> 
> This patch adds the check for kthread termination into the producer.
> It uses the existing kill_test flag to finish the kthreads as
> cleanly as possible.
> 
> It disables printing the "ERROR" message when the kthread is going.
> 
> Also it makes sure that producer does not go into the 10sec sleep
> when it is being killed.

This patch looks like something I may take regardless of the other
patches (if it applies cleanly).

As for the other patches, the ring buffer benchmark is just that, a
benchmark that I use when making changes to the ring buffer. It's not
something for production systems.

What about just adding a depend on !LIVE_PATCHING to
RING_BUFFER_BENCHMARK, or force it to shut down during patching.
There's no reason to make it safe to be running when you patch the
kernel. Just adds complexity to some simple code.

-- Steve
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