Specifications

Red Hat Enterprise Linux to Oracle Solaris Porting Guide

developer to specify how. Within legacy code, execution loops, in particular, often represent

opportunities for optimization where previously repetitive serial operations can be divided into

multiple, independent execution threads. Several compiler flags are used with Oracle Solaris Studio

compilers to govern automatic parallelization behavior:

• The -xautopar compiler flag tells the compiler to look for loops that can be safely parallelized in

the code.

• The -xreduction compiler flag can be used to recognize and parallelize reduction operations that

take a range of values and output a single value, such as summing all the values in an array.

• The -xloopinfo compiler flag can be specified to generate information about loops that the

compiler has parallelized.

Addressing Multithreaded Application Issues

Using Thread Analyzer

The Oracle Solaris Studio Thread Analyzer is an advanced tool for application optimization, and it is

designed to help ensure multithreaded application correctness. Specifically, the Thread Analyzer can

help detect, analyze, and debug the special situations that can arise in multithreaded applications.

Detecting Race Conditions and Deadlocks

Data races can cause incorrect or unpredictable results, and they can occur arbitrarily far way from

where a problem seems to occur. Data races occur under the following conditions:

• Two or more threads in a single process concurrently access the same memory location.

• At least one of the threads is accessing the memory location for writing.

• The threads are not using any exclusive locks to control their accesses to that memory.

Deadlock conditions occur when one thread is blocked waiting on a resource held by a second thread,

while the second thread is blocked waiting on a resource held by the first (or an equivalent situation

with more threads involved).

To instrument the source code for the detection of data race and deadlock issues, the code is compiled

with a special flag, executed under control of the collect -r command, and then loaded into the

Thread Analyzer.

Applications are first compiled with the

-xinstrument=datarace compiler flag. It is recommended

that the

-g flag also be set and that no optimization level be used to help ensure that the line numbers

and call-stacks information are returned correctly.

The resulting application code is then executed within the

collect -r command, allowing for the

collection of key runtime information. Use the

collect –r all option to run the program and

create a data race detection and deadlock detection experiment during the execution of the process.