linux-kernel - Re: [PATCH 1/1] ftrace: adding other non-leaving .text sections

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Message-ID: <20081126031850.GB14685@linux-sh.org>
Date:	Wed, 26 Nov 2008 12:18:50 +0900
From:	Paul Mundt <lethal@...ux-sh.org>
To:	walimis <walimisdev@...il.com>
Cc:	Steven Rostedt <rostedt@...dmis.org>,
	Liming Wang <liming.wang@...driver.com>,
	Ingo Molnar <mingo@...e.hu>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/1] ftrace: adding other non-leaving .text sections

On Wed, Nov 26, 2008 at 11:14:38AM +0800, walimis wrote:
> On Wed, Nov 26, 2008 at 12:04:46PM +0900, Paul Mundt wrote:
> >On Tue, Nov 25, 2008 at 10:03:35PM -0500, Steven Rostedt wrote:
> >> 
> >> On Wed, 26 Nov 2008, Liming Wang wrote:
> >> 
> >> > Please review this patch, and I don't know whether new sections will conflict 
> >> > with sched tracer or others. 
> >> > This patch is against Steven tree's tip/devel latest commit.
> >> > 
> >> > Impact: improve recordmcount.pl
> >> > 
> >> > Besides .text section, there are three .text sections that won't
> >> > be freed after kernel booting. They are: .sched.text, .spinlock.text
> >> > and .kprobes.text, which contain functions we can trace. But the last
> >> > section ".kprobes.text" is particular, which has been marked as "notrace",
> >> > we ignore it. Thus we add other two sections.
> >> 
> >> Yep, only those sections that we know will not disappear are OK. I was
> >> conservative with only using ".text" but I knew there were other sections 
> >> that were OK, so I used the hash array to make it easy to add others.
> >> 
> >Does your .text cover .text.head by the way?
> No, and not needed. Because .text.head is of booting code, to which
> function tracer can't trace.
> 
In the case of CPU hotplug it can be entered at any time. I don't see why
it can't be traced from the boot CPU at least.
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