| From: |
| Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca> |
| To: |
| Ingo Molnar <mingo@elte.hu>, akpm@linux-foundation.org,
Frederic Weisbecker <fweisbec@gmail.com>,
Steven Rostedt <rostedt@goodmis.org>,
LKML <linux-kernel@vger.kernel.org> |
| Subject: |
| [RFC patch 00/21] TIF_KERNEL_TRACE thread flags |
| Date: |
| Sun, 15 Mar 2009 15:03:40 -0400 |
| Message-ID: |
| <20090315190340.229569867@polymtl.ca> |
| Archive‑link: | |
Article |
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
--
Mathieu Desnoyers
OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68
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