LKML Archive on lore.kernel.org
help / color / mirror / Atom feed
From: Peter Zijlstra <a.p.zijlstra@chello.nl>
To: Arjan van de Ven <arjan@infradead.org>
Cc: Pekka Paalanen <pq@iki.fi>, Ingo Molnar <mingo@elte.hu>,
	Christoph Hellwig <hch@infradead.org>,
	linux-kernel@vger.kernel.org
Subject: Re: [RFC PATCH] x86: explicit call to mmiotrace in do_page_fault()
Date: Sat, 09 Feb 2008 19:39:47 +0100	[thread overview]
Message-ID: <1202582388.16505.8.camel@lappy> (raw)
In-Reply-To: <20080209100133.60406c00@laptopd505.fenrus.org>


On Sat, 2008-02-09 at 10:01 -0800, Arjan van de Ven wrote:
> >  	default n
> >  	help
> >  	  This will build a kernel module called mmiotrace.
> > +	  Making this a built-in is heavily discouraged.
> 
> why is this? Wouldn't it be nice if distros just shipped with this in their kernel by default
> for example?

so default m?

> > -#ifdef CONFIG_PAGE_FAULT_HANDLERS
> > -static HLIST_HEAD(pf_handlers); /* protected by RCU */
> > -static DEFINE_SPINLOCK(pf_handlers_writer);
> > +#ifdef CONFIG_MMIOTRACE_HOOKS
> > +static pf_handler_func mmiotrace_pf_handler; /* protected by RCU */
> > +static DEFINE_SPINLOCK(mmiotrace_handler_lock);
> >  
> > -void register_page_fault_handler(struct pf_handler *new_pfh)
> > +int mmiotrace_register_pf(pf_handler_func new_pfh)
> >  {
> > +	int ret = 0;
> >  	unsigned long flags;
> > -	spin_lock_irqsave(&pf_handlers_writer, flags);
> > -	hlist_add_head_rcu(&new_pfh->hlist, &pf_handlers);
> > -	spin_unlock_irqrestore(&pf_handlers_writer, flags);
> > +	spin_lock_irqsave(&mmiotrace_handler_lock, flags);
> > +	if (mmiotrace_pf_handler)
> > +		ret = -EBUSY;
> > +	else
> > +		mmiotrace_pf_handler = new_pfh;
> > +	spin_unlock_irqrestore(&mmiotrace_handler_lock, flags);
> > +	return ret;
> >  }
> > -EXPORT_SYMBOL_GPL(register_page_fault_handler);
> > +EXPORT_SYMBOL_GPL(mmiotrace_register_pf);
> 
> why not use a weak function instead? should be a ton simpler.

AFAIC weak functions are a built time thing, not fixed up on module
load. So I'm not seeing the applicability there.

Also, it would force a function call, even for the unlikely case the
tracer is set.




  parent reply	other threads:[~2008-02-09 18:40 UTC|newest]

Thread overview: 43+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-01-27 16:52 [PATCH] x86: Add a list for custom page fault handlers Pekka Paalanen
2008-01-27 17:55 ` [RFC PATCH] x86: mmiotrace - trace memory mapped IO Pekka Paalanen
2008-01-30 22:39   ` Pekka Paalanen
2008-01-27 19:29 ` [PATCH] x86: Add a list for custom page fault handlers Ingo Molnar
2008-01-27 21:03 ` Peter Zijlstra
2008-01-30  2:28 ` Harvey Harrison
2008-01-30  2:34   ` Harvey Harrison
2008-01-30 18:08     ` Pekka Paalanen
2008-01-31 15:07       ` Ingo Molnar
2008-01-31 16:02         ` [PATCH v2] " Pekka Paalanen
2008-01-31 16:15           ` Arjan van de Ven
2008-02-03  6:55             ` Pekka Paalanen
2008-02-03  7:03               ` Ingo Molnar
2008-02-03 21:40                 ` Pekka Paalanen
2008-02-05 20:28                 ` [PATCH 1/4] x86 mmiotrace: use lookup_address() Pekka Paalanen
2008-02-05 20:30                   ` [PATCH 2/4] x86 mmiotrace: fix relay-buffer-full flag for SMP Pekka Paalanen
2008-02-05 20:44                     ` Eric Dumazet
2008-02-05 21:14                       ` Pekka Paalanen
2008-02-05 21:35                         ` Eric Dumazet
2008-02-09 17:53                           ` [PATCH] x86 mmiotrace: Use percpu instead of arrays Pekka Paalanen
2008-02-05 20:31                   ` [PATCH 3/4] x86 mmiotrace: comment about user space ABI Pekka Paalanen
2008-02-05 20:39                   ` [PATCH 4/4] x86 mmiotrace: move files into arch/x86/mm/ Pekka Paalanen
2008-02-06  3:02                     ` Randy Dunlap
2008-02-09 11:21                       ` Pekka Paalanen
2008-02-07 12:53                     ` Ingo Molnar
2008-02-07 12:56                       ` Christoph Hellwig
2008-02-09 17:52                         ` [RFC PATCH] x86: explicit call to mmiotrace in do_page_fault() Pekka Paalanen
2008-02-09 18:01                           ` Arjan van de Ven
2008-02-09 18:23                             ` Pekka Paalanen
2008-02-09 18:56                               ` Pekka Enberg
2008-02-09 19:11                                 ` Pekka Paalanen
2008-02-09 19:19                                   ` Pekka Enberg
2008-02-09 18:39                             ` Peter Zijlstra [this message]
2008-02-09 18:39                           ` Peter Zijlstra
2008-02-10 18:05                             ` [RFC PATCH v2] " Pekka Paalanen
2008-02-11  2:12                               ` Pavel Roskin
2008-02-11 18:04                                 ` Pekka Paalanen
2008-02-06  5:00                   ` [PATCH 1/4] x86 mmiotrace: use lookup_address() Christoph Hellwig
2008-02-07 12:52                     ` Ingo Molnar
2008-01-31 16:16           ` [RFC PATCH v2] x86: mmiotrace - trace memory mapped IO Pekka Paalanen
2008-01-31 16:29             ` Arjan van de Ven
2008-02-03  7:21               ` Pekka Paalanen
2008-01-30 18:20 ` [PATCH] x86: Add a list for custom page fault handlers Arjan van de Ven

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=1202582388.16505.8.camel@lappy \
    --to=a.p.zijlstra@chello.nl \
    --cc=arjan@infradead.org \
    --cc=hch@infradead.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=mingo@elte.hu \
    --cc=pq@iki.fi \
    --subject='Re: [RFC PATCH] x86: explicit call to mmiotrace in do_page_fault()' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).