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Message-Id: <20090315190340.229569867@polymtl.ca>
Date: Sun, 15 Mar 2009 15:03:40 -0400
From: Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>
To: Ingo Molnar <mingo@...e.hu>, akpm@...ux-foundation.org,
Frederic Weisbecker <fweisbec@...il.com>,
Steven Rostedt <rostedt@...dmis.org>,
LKML <linux-kernel@...r.kernel.org>
Subject: [RFC patch 00/21] TIF_KERNEL_TRACE thread flags
Hello,
This is the implementatino of TIF_KERNEL_TRACE thread flags I did in the LTTng
tree. Basically, it offers :
- Setting a per-thread flag for _all_ threads to enable system-wide syscall
tracing.
- No performance impact when disabled, no need to stop threads upon
activation/deactivation (does not add latency to userspace threads upon
activation).
The most tricky bits are in the x86_64 architecture, because its entry_64.S
code does not expect the thread flags to be changed concurrently while the
thread is running. I modified entry_64.S so that the architecture does not
suffer of any performance impact when syscall audit or secure computing is
enabled, but tests for the TIF_KERNEL_TRACE flag upon return to userspace too.
Given this looks very much like what Frederic is currently doing, I think it's
good to post it for comments.
utrace tracehooks could potentially make this patchset obsolete, but I an not
yet convinced that utrace offers the same low-latency guarantees as this code.
It applies on top of kernel 2.6.29-rc7.
Mathieu
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Mathieu Desnoyers
OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68
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