From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
To: Oleg Nesterov <oleg@redhat.com>
Cc: Ingo Molnar <mingo@elte.hu>,
Ananth N Mavinakayanahalli <ananth@in.ibm.com>,
Anton Arapov <anton@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>,
Peter Zijlstra <peterz@infradead.org>,
Roland McGrath <roland@hack.frob.com>,
Srikar Dronamraju <srikar@linux.vnet.ibm.com>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 0/2] ptrace: DEBUGCTLMSR_BTF fixes
Date: Mon, 06 Aug 2012 18:14:45 +0200 [thread overview]
Message-ID: <501FED75.5060206@linutronix.de> (raw)
In-Reply-To: <20120803162912.GA19767@redhat.com>
On 08/03/2012 06:29 PM, Oleg Nesterov wrote:
> Assuming this series passes the review of course. And it would
> be really nice if someone reviews 2/2, I am not confident that
> I fully understand this DEBUGCTLMSR_BTF magic.
Here is how the processor disables the BTF:
| The processor clears the BTF flag when it generates a debug
| exception. The debugger must set the BTF flag before resuming program
| execution to continue single-stepping on branches.
This was a quote from "253668-039US, May 2011" page 16-17.
So I think __switch_to_extra() should set the bit before putting the
task on the CPU. If this bit is enabled on the wrong CPU then in will
remain set forever if single steeping has not been / will not be
enabled.
> Oleg.
>
Sebastian
next prev parent reply other threads:[~2012-08-06 16:15 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-08-03 16:29 [PATCH 0/2] ptrace: DEBUGCTLMSR_BTF fixes Oleg Nesterov
2012-08-03 16:29 ` [PATCH 1/2] ptrace: introduce set_task_blockstep() helper Oleg Nesterov
2012-08-03 16:29 ` [PATCH 2/2] ptrace: fix set_task_blockstep()->update_debugctlmsr() logic Oleg Nesterov
2012-08-03 16:43 ` Sebastian Andrzej Siewior
2012-08-03 17:38 ` Oleg Nesterov
2012-08-03 18:28 ` Sebastian Andrzej Siewior
2012-08-07 15:13 ` Oleg Nesterov
2012-08-07 9:41 ` Sebastian Andrzej Siewior
2012-08-07 10:52 ` Sebastian Andrzej Siewior
2012-08-07 15:15 ` Oleg Nesterov
2012-08-07 15:29 ` Sebastian Andrzej Siewior
2012-08-07 15:31 ` Oleg Nesterov
2012-08-07 15:12 ` Oleg Nesterov
2012-08-06 16:14 ` Sebastian Andrzej Siewior [this message]
2012-08-07 15:15 ` [PATCH 0/2] ptrace: DEBUGCTLMSR_BTF fixes Oleg Nesterov
2012-08-07 15:38 ` Sebastian Andrzej Siewior
2012-08-07 15:46 ` Oleg Nesterov
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=501FED75.5060206@linutronix.de \
--to=bigeasy@linutronix.de \
--cc=ananth@in.ibm.com \
--cc=anton@redhat.com \
--cc=hpa@zytor.com \
--cc=linux-kernel@vger.kernel.org \
--cc=mingo@elte.hu \
--cc=oleg@redhat.com \
--cc=peterz@infradead.org \
--cc=roland@hack.frob.com \
--cc=srikar@linux.vnet.ibm.com \
/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
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox