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  1. 22 Jan, 2009 2 commits
    • Steven Rostedt's avatar
      trace: do not disable wake up tracer on output of trace · 5bc4564b
      Steven Rostedt authored 
      Impact: fix to erased trace output

To try not to have the outputing of a trace interfere with the wakeup
tracer, it would disable tracing while the output was printing. But
if a trace had started when it was disabled, it can show a partial
trace. To try to solve this, on closing of the tracer, it would
clear the trace buffer.

The latency tracers (wakeup and irqsoff) have two buffers. One for
recording and one for holding the max trace that is printed. The
clearing of the trace above should only affect the recording buffer.
But for some reason it would move the erased trace to the print
buffer. Probably due to a race with the closing of the trace and
the saving ofhe max race.

The above is all pretty useless, and if the user does not want the
printing of the trace to be traced itself, then the user can manual
disable tracing. This patch removes all the code that tries to keep
the output of the tracer from modifying the trace.
Signed-off-by: default avatarSteven Rostedt <srostedt@redhat.com>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
      5bc4564b
    • Ingo Molnar's avatar
      Merge branch 'tracing/ftrace' into tracing/core · 03b30d15
      Ingo Molnar authored
      03b30d15
  3. 20 Jan, 2009 7 commits
  5. 18 Jan, 2009 2 commits
    • Steven Rostedt's avatar
      ftrace: test for running of recordmcount.pl twice on an object · b43f7093
      Steven Rostedt authored 
      Impact: fix failure of dynamic function tracer selftest

In a course of development, a developer does several makes on their
kernel. Sometimes, the make might do something abnormal. In the
case of running the recordmcount.pl script on an object twice,
the script will duplicate all the calls to mcount in the __mcount_loc
section.

On boot up, the dynamic function tracer is careful when it modifies
code, and performs several consistency checks. One is to not modify
the call site if it is not what it expects it to be. If a function
call site is listed twice, the first entry will convert the site
to a nop, and the second will fail because it expected to see a
call to mcount, but instead it sees a nop. Thus, the function tracer
is disabled.

Eric Sesterhenn reported seeing:

[    1.055440] ftrace: converting mcount calls to 0f 1f 44 00 00
[    1.055568] ftrace: allocating 29418 entries in 116 pages
[    1.061000] ------------[ cut here ]------------
[    1.061000] WARNING: at kernel/trace/ftrace.c:441

 [...]

[    1.060000] ---[ end trace 4eaa2a86a8e2da23 ]---
[    1.060000] ftrace failed to modify [<c0118072>] check_corruption+0x3/0x2d
[    1.060000]  actual: 0f:1f:44:00:00

This warning shows that check_corruption+0x3 already had a nop in
its place (0x0f1f440000). After compiling another kernel the problem
went away.

Later Eric Paris notice the same type of issue. Luckily, he saved
the vmlinux file that caused it. In the file we found a bunch of
duplicate mcount call site records, which lead us to the script.

Perhaps this problem only happens to people named Eric.

This patch changes the script to test if the __mcount_loc already
exists in the object file, and if it does, it will print out
an error message and kill the compile.
Reported-by: default avatarEric Sesterhenn <snakebyte@gmx.de>
Reported-by: default avatarEric Paris <eparis@redhat.com>
Signed-off-by: default avatarSteven Rostedt <srostedt@redhat.com>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
      b43f7093
    • Ingo Molnar's avatar
      Merge branch 'tracing/ftrace'; commit 'v2.6.29-rc2' into tracing/core · 4092762a
      Ingo Molnar authored
      4092762a
  7. 16 Jan, 2009 29 commits
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