From mboxrd@z Thu Jan  1 00:00:00 1970
From: "Shi, Yang" <yang.shi@linaro.org>
Subject: Re: [PATCH] bpf: convert hashtab lock to raw lock
Date: Mon, 02 Nov 2015 09:31:50 -0800
Message-ID: <56379E06.3040008@linaro.org>
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Cc: Daniel Borkmann <daniel@iogearbox.net>,
	Alexei Starovoitov <alexei.starovoitov@gmail.com>,
	ast@kernel.org, linux-kernel@vger.kernel.org,
	linux-rt-users@vger.kernel.org, netdev@vger.kernel.org,
	linaro-kernel@lists.linaro.org
To: Steven Rostedt <rostedt@goodmis.org>
Return-path: <netdev-owner@vger.kernel.org>
In-Reply-To: <20151102122405.56dd97a1@gandalf.local.home>
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List-Id: linux-rt-users.vger.kernel.org

On 11/2/2015 9:24 AM, Steven Rostedt wrote:
> On Mon, 02 Nov 2015 09:12:29 -0800
> "Shi, Yang" <yang.shi@linaro.org> wrote:
>
>> Yes, it is common practice for converting sleepable spin lock to raw
>> spin lock in -rt to avoid scheduling in atomic context bug.
>
> Note, in a lot of cases we don't just convert spin_locks to raw because
> of atomic context. There's times we need to change the design where the
> lock is not taken in atomic context (switching preempt_disable() to a
> local_lock() for example).

Yes, definitely. Understood.

Thanks,
Yang

>
> But bpf is much like ftrace and kprobes where they can be taken almost
> anywhere, and the do indeed need to be raw.
>
> -- Steve
>