linux-kernel - Re: [RFC,PATCH 14/14] utrace core

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Message-ID: <20091124204152.GA9131@redhat.com>
Date:	Tue, 24 Nov 2009 21:41:52 +0100
From:	Oleg Nesterov <oleg@...hat.com>
To:	Andi Kleen <andi@...stfloor.org>
Cc:	Alexey Dobriyan <adobriyan@...il.com>,
	Ananth Mavinakayanahalli <ananth@...ibm.com>,
	Christoph Hellwig <hch@...radead.org>,
	"Frank Ch. Eigler" <fche@...hat.com>, Ingo@...stfloor.org,
	"Molnar <mingo"@firstfloor.org, utrace-devel@...hat.com,
	linux-kernel@...r.kernel.org
Subject: Re: [RFC,PATCH 14/14] utrace core

On 11/24, Andi Kleen wrote:
>
> Oleg Nesterov <oleg@...hat.com> writes:
>
> > From: Roland McGrath <roland@...hat.com>
> >
> > This adds the utrace facility, a new modular interface in the kernel
> > for implementing user thread tracing and debugging.  This fits on top
> > of the tracehook_* layer, so the new code is well-isolated.
>
> Could we just drop the tracehook layer if this finally merged
> and call the low level functions directly?

Not sure I understand. Tracehooks are trivial inline wrappers on
top utrace calls,

> It might have been reasonably early on when it was still out of tree,
> but longer term when it's integrated having strange opaque hooks
> like that just makes the coder harder to read and maintain.

Well, I don't think the code will be better if we remove tracehooks.

For example. tracehook_report_syscall_entry() has a lot of callers
in arch/, each callsite should be changed to do

	if ((task_utrace_flags(current) & UTRACE_EVENT(SYSCALL_ENTRY)) &&
		utrace_report_syscall_entry(regs))
		ret = -1; // this depends on machine

instead of simply calling tracehook_report_syscall_entry().

What is the point?

But again, perhaps I misunderstood you.

Oleg.

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