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author | Lai Jiangshan <laijs@cn.fujitsu.com> | 2010-01-06 20:08:50 +0800 |
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committer | Steven Rostedt <rostedt@goodmis.org> | 2010-01-06 12:51:34 -0500 |
commit | 7e53bd42d14c75192b99674c40fcc359392da59d (patch) | |
tree | 65c3638604a2c03947da5cbd7ffb3e4dfee66370 /scripts/recordmcount.pl | |
parent | 0fa0edaf32b9a78b9854f1da98d4511a501089b0 (diff) | |
download | linux-stable-7e53bd42d14c75192b99674c40fcc359392da59d.tar.gz linux-stable-7e53bd42d14c75192b99674c40fcc359392da59d.tar.bz2 linux-stable-7e53bd42d14c75192b99674c40fcc359392da59d.zip |
tracing: Consolidate protection of reader access to the ring buffer
At the beginning, access to the ring buffer was fully serialized
by trace_types_lock. Patch d7350c3f4569 gives more freedom to readers,
and patch b04cc6b1f6 adds code to protect trace_pipe and cpu#/trace_pipe.
But actually it is not enough, ring buffer readers are not always
read-only, they may consume data.
This patch makes accesses to trace, trace_pipe, trace_pipe_raw
cpu#/trace, cpu#/trace_pipe and cpu#/trace_pipe_raw serialized.
And removes tracing_reader_cpumask which is used to protect trace_pipe.
Details:
Ring buffer serializes readers, but it is low level protection.
The validity of the events (which returns by ring_buffer_peek() ..etc)
are not protected by ring buffer.
The content of events may become garbage if we allow another process to consume
these events concurrently:
A) the page of the consumed events may become a normal page
(not reader page) in ring buffer, and this page will be rewritten
by the events producer.
B) The page of the consumed events may become a page for splice_read,
and this page will be returned to system.
This patch adds trace_access_lock() and trace_access_unlock() primitives.
These primitives allow multi process access to different cpu ring buffers
concurrently.
These primitives don't distinguish read-only and read-consume access.
Multi read-only access is also serialized.
And we don't use these primitives when we open files,
we only use them when we read files.
Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
LKML-Reference: <4B447D52.1050602@cn.fujitsu.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Diffstat (limited to 'scripts/recordmcount.pl')
0 files changed, 0 insertions, 0 deletions