linux-kernel - Re: [RFC PATCH 1/3] Unified trace buffer

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Thu, 25 Sep 2008 21:27:44 -0400 (EDT)
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Jeremy Fitzhardinge <jeremy@...p.org>
cc:	Ingo Molnar <mingo@...e.hu>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Martin Bligh <mbligh@...gle.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Martin Bligh <mbligh@...igh.org>, linux-kernel@...r.kernel.org,
	Thomas Gleixner <tglx@...utronix.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	prasad@...ux.vnet.ibm.com,
	Mathieu Desnoyers <compudj@...stal.dyndns.org>,
	"Frank Ch. Eigler" <fche@...hat.com>,
	David Wilder <dwilder@...ibm.com>, hch@....de,
	Tom Zanussi <zanussi@...cast.net>,
	Steven Rostedt <srostedt@...hat.com>
Subject: Re: [RFC PATCH 1/3] Unified trace buffer

On Thu, 25 Sep 2008, Jeremy Fitzhardinge wrote:
> 
> No, as I said:  "You just need to emit the current
> tsc+frequency+wallclock time before you emit any more delta records
> after the frequency change."
> 
> When an event which affects the tsc occurs, like a frequency change or
> pause, set a flag.  When you're next about to emit a delta, check the
> flag and emit new timing parameters (or instead).

This is where I get confused.  When do we add this to the trace buffer?
Every record (currently) records the delta time from the last event.
If a frequency changes, do we need to record the tuple at that moment?

If so, we have an issue. We can be in the middle of tracing the GTOD
and we can not recurse back into the GTOD for fear of deadlocking on
the GTOD spinlocks.

Do we add this data to the buffers when it happens?  This means every
allocated ring buffer (and yes you can have more than one), will need to
register a call back so that it can record this information into the
buffer.

Or am I just not getting it?

-- Steve

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/