JavaScript is required to for searching.
Skip Navigation Links
Exit Print View
Oracle Solaris Dynamic Tracing Guide     Oracle Solaris 11 Information Library
search filter icon
search icon

Document Information


1.  About DTrace

2.  D Programming Language

3.  Aggregations

4.  Actions and Subroutines

5.  Buffers and Buffering

6.  Output Formatting

7.  Speculative Tracing

8.  dtrace(1M) Utility

9.  Scripting

10.  Options and Tunables

11.  Providers

12.  User Process Tracing

copyin and copyinstr Subroutines

Avoiding Errors

Eliminating dtrace(1M) Interference

syscall Provider

ustack Action

uregs[] Array

pid Provider

User Function Boundary Tracing

Tracing Arbitrary Instructions

13.  Statically Defined Tracing for User Applications

14.  Security

15.  Anonymous Tracing

16.  Postmortem Tracing

17.  Performance Considerations

18.  Stability

19.  Translators

20.  Versioning

Eliminating dtrace(1M) Interference

If you trace every call to the write(2) system call, you will cause a cascade of output. Each call to write causes the dtrace(1M) command to call write as it displays the output, and so on. This feedback loop is a good example of how the dtrace command can interfere with the desired data. You can use a simple predicate to prevent these unwanted data from being traced:

/pid != $pid/
        printf("%s", stringof(copyin(arg1, arg2)));

The $pid macro variable expands to the process identifier of the process that enabled the probes. The pid variable contains the process identifier of the process whose thread was running on the CPU where the probe was fired. Therefore the predicate /pid != $pid/ ensures that the script does not trace any events related to the running of this script itself.