Intel® Advisor User Guide

User Guide

Contents

Dangling Lock

Occurs when a task does not release a lock before the task ends.
Problem type: Dangling lock
ID
Code Location
Description
1
Allocation site
If present, represents the location and associated call stack when the lock was created.
2
Lock owned
If present, represents the location and its associated call stack when the lock was last acquired.
3
Parallel site
If present, represents the location and associated call stack of the site-begin annotation of the parallel site containing the task that acquired the lock.
Example
void problem()
{
    ANNOTATE_SITE_BEGIN(dangle_site1);        // Parallel site
        ANNOTATE_TASK_BEGIN(task1);
            ANNOTATE_LOCK_ACQUIRE(&dangle);   // Lock owned
        ANNOTATE_TASK_END();
     // ...
    ANNOTATE_SITE_END();
}
In this example:
  • There is a parallel site that contains a task.
  • The lock is acquired in the task.
  • The lock is not released before the end of the task - the
    ANNOTATE_LOCK_RELEASE()
     annotation is missing.
Possible Correction Strategies
  • Make sure that an
    ANNOTATE_LOCK_RELEASE(address)
     annotation is executed on every flow path from an
    ANNOTATE_LOCK_ACQUIRE(address)
     annotation to the end of the task. If a code region has multiple exit flow paths, make sure the lock is released on all the paths.
  • Consider putting the lock-acquire and lock-release in the constructor and destructor of a static object, so that lock release happens automatically.
  • Consider putting a lock release in an exception handler if a the locked region might exit from an exception.

Product and Performance Information

1

Performance varies by use, configuration and other factors. Learn more at www.Intel.com/PerformanceIndex.