Pane: Analysis Type-Threading Errors

Pane position in window

Before Analysis

(One way) To access this Intel Inspector pane: Choose File > New > Analysis.... Then choose Threading Error Analysis from the Analysis Type drop-down list.

Use this pane on the Analysis Type window to:

  • Choose and, if necessary, fine-tune a preset threading error analysis type.

  • Configure a threading error analysis to investigate problems in an interactive debugging session.

Tip

If the combination of analysis type settings in the preset threading error analysis types does not meet your needs at all, try creating a custom threading error analysis type.

During Analysis

To access this pane: Click the Analysis Type button on the Navigation toolbar.

Use this to review the analysis type settings for this analysis run.

After Analysis Is Complete

To access this pane: Click the Analysis Type button on the Navigation toolbar.

Use this pane to:

  • Review the analysis type settings for this analysis run.

  • Re-inspect - run another analysis using the same analysis type settings.

Use This

To Do This

Analysis Type drop-down list

Switch to another category of analysis types.

Configuration slider

Choose a preset analysis type (drag slider).

Analysis Time Overhead gauge

Analysis Time gauge

Quickly estimate the time it may take to collect a result using various preset analysis types. Time is expressed in relation to normal application execution time.

For example, 2x - 20x is 2 to 20 times longer than normal application execution time. If normal application execution time is 5 seconds, estimated collection time is 10 to 100 seconds.

Memory Overhead gauge

Memory Overhead gauge

The Memory Overhead gauge helps you quickly estimate the memory the Intel Inspector may consume to detect errors using this preset analysis type. Memory is expressed in blue-filled bars.

Note

The gauge does not show memory used by the running application during analysis.

Copy button

Create a new custom analysis type based on the currently selected analysis type.

Analyze without debugger radio button

Select to run an analysis without launching an interactive debugging session. Useful for investigating all types of memory and threading problems.

Tip

You can later use the Debug This Problem function from within a result to launch a new analysis in conjunction with a debugger to stop at problems of interest. The rerun analysis is automatically focused to find the selected problems, making it return to the problems more quickly. The Debug This Problem function is the recommended method for investigating threading errors in an interactive debugging session.

Enable debugger when problem detected radio button

Select to allow investigation of every problem detected in an interactive debugging session. Useful for investigating all types of memory problems except memory and resource leaks.

Select analysis start location with debugger radio button

Select to allow investigation of problems in a particular area of code during an interactive debugging session. Typical scenario: You need to check for errors in a specific section of application code, but the Intel Inspector does not provide the appropriate granularity to analyze only that code section. This option quickly takes you near that execution point in a debugging session. Useful for investigating all types of memory problems except memory and resource leaks.

Tip

You can also use this option to investigate all types of threading errors, but it may be quicker to use the Debug This Problem function in a result if you plan to investigate a single threading problem.

Configurable Threading Error Analysis Type Settings

The following list shows the configurable settings (in alphabetical order) for preset threading analysis types. Configurable means you can change the setting without creating a custom analysis type.

  • Remove duplicates checkbox (configurable for the Locate Deadlocks and Data Races analysis type only)

  • Scope drop-down list (configurable for the Locate Deadlocks and Data Races analysis type only)
  • Stack frame depth drop-down list

  • Terminate on deadlock checkbox

  • Use maximum resources checkbox (configurable for the Locate Deadlocks and Data Races analysis type only)

Threading Error Analysis Type Settings

Use the Details region to review current analysis type settings. The following table describes the purpose, usefulness, and cost (low, medium, high, or proportional in terms of time and resources) for each threading error analysis type configuration setting. (The settings are listed in alphabetical order.)

Setting

Purpose, Usefulness, and Cost

Cross-thread stack access detection

Use to set the alert mechanism for when a thread accesses stack memory of another thread.

The alert mechanism helps you decide if this is an issue that requires handling.

All options are low cost if Detect data races is selected.

Recommendation:

  • Use Hide problems/Hide warnings if using an OpenMP* or Intel® Threading Building Blocks programming model; or if cross-thread stack accesses are anticipated. Also select Detect races on stack.

  • Use Hide problems/Show warnings if cross-thread stack accesses are not anticipated. Also deselect Detect data races on stack.

  • Use Show problems/Hide warnings if cross-thread stack accesses are not anticipated but a previous analysis indicated they exist and you are not using an OpenMP* or Intel Threading Building Blocks programming model. Also deselect Detect data races on stack.

Detect data races

Select to detect problems where multiple threads access the same memory location without proper synchronization and at least one access is a write.

Selecting is useful when you suspect data races that are not yet evident.

High cost.

Recommendation: Select. Consider also deselecting Use maximum resources to reduce cost.

Detect data races on stack (previously called Detect data races on stack accesses)

Available only if Detect data races is selected.

Select to detect data races for variables allocated on the stack.

Selecting is useful when threads in an application share variables from the stack and you suspect data races on the variables.

High cost.

Recommendation: Deselect. If you select, consider also deselecting Use maximum resources to reduce cost.

Detect deadlocks

Select to detect problems where two or more threads are waiting for the other to release resources, but none of the threads releases the resources. Thus no thread can proceed.

Selecting is useful when you want to troubleshoot the location of a deadlock.

Low cost.

Detect lock hierarchy violations

Select to detect problems where the acquisition hierarchy order of multiple synchronization objects in one thread differs from the acquisition hierarchy order in another thread, and could cause a deadlock under certain conditions.

Selecting is useful when an application has complicated synchronization and it is hard to verify correctness.

Low cost unless an application has a significant number of locks.

Race analysis byte granularity (previously called Memory access byte granularity)

Available only if Detect data races is selected.

Use to set the size of the smallest memory block the Intel Inspector considers a single block of memory when determining if non-synchronized accesses to a memory block constitute a data race.

Selecting is useful to control memory consumption during analysis for some applications.

High cost when set to 1 byte.

Recommendation: Set to 4 unless you continually see data races based on safe access to smaller memory blocks. If so, reset to 1.

Remove duplicates

Deselect to show all occurrences of a detected problem in the Code Locations pane.

Deselecting is:

  • Useful when you need to fully visualize all threads and problem occurrences in relation to time

  • Low cost in terms of time; however, the number of duplicate errors could crowd out the number of unique errors.

Recommendation: Select.

Save stack on first access

Available only if Detect data races is selected.

Select to show as much information as possible on all threads involved in a data race.

Selecting is useful when investigating complex data race problems.

High cost.

Recommendation: Deselect on initial analysis runs. Select only when you need the maximum information and context about all threads involved in a data race to solve the problem.

Save stack on lock creation

Select to show creation information on synchronization objects involved in deadlocks, lock hierarchy violations, and data races.

Selecting is useful when acquisition stacks are not sufficient to understand the problem.

Low cost.

Save stack on memory allocation (previously called Save stack on allocation)

Available only if Detect data races is selected.

Select to identify the allocation site of dynamically allocated memory objects involved in data races.

Medium cost.

Recommendation: Select when you need to identify the object hierarchy of low-level objects involved in data races. For example: If object R is involved in a data race and is instantiated within objects O1, O2, and O3, the allocation call stack can help you identify which encapsulating object is not properly protecting access to object R.

Stack frame depth

Use to provide more or less call stack context for detected errors.

A high setting is useful when analyzing highly object-oriented applications.

A higher number does not significantly impact cost with one exception: Choosing a higher number plus selecting Save stack on first access increases cost.

Recommendation: Use only as large a value as an application requires to display complete call paths.

Terminate on deadlock

Available only if Detect deadlocks is selected.

Select to stop analysis and application execution if the Intel Inspector detects a deadlock.

Selecting is useful when running your application as part of a kernel or unit testing suite.

Low cost.

Recommendation: Deselect. Instead, use the corresponding knob in the command line interface to perform kernel or unit testing in a nightly scenario. If the Intel Inspector identifies a deadlock, decide if it is appropriate to continue analysis.

Use maximum resources

Select to potentially find more problems.

High cost.

Recommendation: Deselect to run a quicker analysis that should find most of your data race and cross-thread stack access problems. Once you have found and fixed these problems, select to get more complete analysis coverage of possible data race and cross-thread stack access problems.

For more complete information about compiler optimizations, see our Optimization Notice.