linux-kernel - Re: [PATCH] bpf: convert hashtab lock to raw lock

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Message-ID: <20151102122405.56dd97a1@gandalf.local.home>
Date:	Mon, 2 Nov 2015 12:24:05 -0500
From:	Steven Rostedt <rostedt@...dmis.org>
To:	"Shi, Yang" <yang.shi@...aro.org>
Cc:	Daniel Borkmann <daniel@...earbox.net>,
	Alexei Starovoitov <alexei.starovoitov@...il.com>,
	ast@...nel.org, linux-kernel@...r.kernel.org,
	linux-rt-users@...r.kernel.org, netdev@...r.kernel.org,
	linaro-kernel@...ts.linaro.org
Subject: Re: [PATCH] bpf: convert hashtab lock to raw lock

On Mon, 02 Nov 2015 09:12:29 -0800
"Shi, Yang" <yang.shi@...aro.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).

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

-- Steve

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