LKML Archive on lore.kernel.org
help / color / mirror / Atom feed
From: Alan Stern <stern@rowland.harvard.edu>
To: Roland McGrath <roland@redhat.com>
Cc: Prasanna S Panchamukhi <prasanna@in.ibm.com>,
	Kernel development list <linux-kernel@vger.kernel.org>
Subject: Re: [RFC] hwbkpt: Hardware breakpoints (was Kwatch)
Date: Fri, 6 Jul 2007 16:48:59 -0400 (EDT)	[thread overview]
Message-ID: <Pine.LNX.4.44L0.0707061637530.4777-100000@iolanthe.rowland.org> (raw)
In-Reply-To: <20070628023100.E46AB4D05E6@magilla.localdomain>

On Wed, 27 Jun 2007, Roland McGrath wrote:

> In the first battle just to make it compile, the only issue was that you
> assume every machine has TIF_DEBUG, which is in fact an implementation
> detail chosen lately by i386 and x86_64.  AFAIK the only reason for it
> there is just to make a cheap test of multiple bits in the hot path
> deciding to call __switch_to_xtra.  Do you rely on it meaning something
> more precise than just being a shorthand for hw_breakpoint_info!=NULL?

Going over the code, I remembered that TIF_DEBUG really does mean moree
than just hw_breakpoint_info != NULL.  It means that the thread
actually has some breakpoints registered.

Why keep the hw_breakpoint_info structure if there are no registered 
breakpoints?  I did it so that the virtualized DR[0-3] values would 
remain intact.

For other processors that have only one debug register, this won't
matter so much.  But of course there are references to TIF_DEBUG in the 
arch-independent code.  Do you think there would be any problem about 
reserving a bit for TIF_DEBUG in the other architectures?

Alan Stern

P.S.: I'm just now getting around to doing the stuff we discussed last
week.  It has been a busy time...  At OLS somebody asked when 
hw-breakpoint would get into the mainline.  I guessed that it would be 
a few months before it is added to -mm.  Solving this 
pre/post-notification issue will be difficult.


  parent reply	other threads:[~2007-07-06 20:49 UTC|newest]

Thread overview: 48+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <20070628023100.E46AB4D05E6@magilla.localdomain>
2007-06-29  3:36 ` Alan Stern
2007-07-06 20:48 ` Alan Stern [this message]
2007-02-24  0:08 [PATCH] Kwatch: kernel watchpoints using CPU debug registers Roland McGrath
2007-03-02 17:19 ` [RFC] hwbkpt: Hardware breakpoints (was Kwatch) Alan Stern
2007-03-05  7:01   ` Roland McGrath
2007-03-05 13:36     ` Christoph Hellwig
2007-03-05 16:16       ` Alan Stern
2007-03-05 16:49         ` Christoph Hellwig
2007-03-05 22:04         ` Roland McGrath
2007-03-05 17:25     ` Alan Stern
2007-03-06  3:13       ` Roland McGrath
2007-03-06 15:23         ` Alan Stern
2007-03-07  3:49           ` Roland McGrath
2007-03-07 19:11             ` Alan Stern
2007-03-09  6:52               ` Roland McGrath
2007-03-09 18:40                 ` Alan Stern
2007-03-13  8:00                   ` Roland McGrath
2007-03-13 13:07                     ` Alan Cox
2007-03-13 18:56                     ` Alan Stern
2007-03-14  3:00                       ` Roland McGrath
2007-03-14 19:11                         ` Alan Stern
2007-03-28 21:39                           ` Roland McGrath
2007-03-29 21:35                             ` Alan Stern
2007-04-13 21:09                             ` Alan Stern
2007-05-11 15:25                             ` Alan Stern
2007-05-13 10:39                               ` Roland McGrath
2007-05-14 15:42                                 ` Alan Stern
2007-05-14 21:25                                   ` Roland McGrath
2007-05-16 19:03                                     ` Alan Stern
2007-05-23  8:47                                       ` Roland McGrath
2007-06-01 19:39                                         ` Alan Stern
2007-06-14  6:48                                           ` Roland McGrath
2007-06-19 20:35                                             ` Alan Stern
2007-06-25 10:52                                               ` Roland McGrath
2007-06-25 15:36                                                 ` Alan Stern
2007-06-26 20:49                                                   ` Roland McGrath
2007-06-27  3:26                                                     ` Alan Stern
2007-06-27 21:04                                                       ` Roland McGrath
2007-06-29  3:00                                                         ` Alan Stern
2007-07-11  6:59                                                           ` Roland McGrath
2007-06-28  3:02                                                       ` Roland McGrath
2007-06-25 11:32                                               ` Roland McGrath
2007-06-25 15:37                                                 ` Alan Stern
2007-06-25 20:51                                                 ` Alan Stern
2007-06-26 18:17                                                   ` Roland McGrath
2007-06-27  2:43                                                     ` Alan Stern
2007-05-17 20:39                                 ` Alan Stern
2007-03-16 21:07                         ` Alan Stern
2007-03-22 19:44                         ` Alan Stern

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=Pine.LNX.4.44L0.0707061637530.4777-100000@iolanthe.rowland.org \
    --to=stern@rowland.harvard.edu \
    --cc=linux-kernel@vger.kernel.org \
    --cc=prasanna@in.ibm.com \
    --cc=roland@redhat.com \
    --subject='Re: [RFC] hwbkpt: Hardware breakpoints (was Kwatch)' \
    /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).