Please enable JavaScript.
Coggle requires JavaScript to display documents.
10.2 Avoiding and Diagnosing Deadlocks - Coggle Diagram
10.2 Avoiding and Diagnosing Deadlocks
General Deadlock Avoidance
Single-lock strategy
Programs acquiring only one lock at a time cannot deadlock
Simple but impractical in complex systems
Multi-lock strategy
Lock ordering must be part of design
Minimize potential locking interactions
Document lock-ordering protocol
Fine-grained locking
Use a two-part strategy:
Identify locations where multiple locks may be acquired
Perform global analysis to check consistent lock ordering
Open calls simplify deadlock detection
Makes multiple lock acquisition easier to spot
Enables code review or automated analysis
Timed Lock Attempts
Use tryLock with timeout (explicit Lock classes)
Alternative to intrinsic locking (synchronized)
Allows timeout and failure handling
When timed lock fails:
Log failure
Record context
Attempt graceful recovery (instead of crashing)
Timed locking for multiple locks:
Can break deadlocks by:
Releasing held locks
Backing off and retrying
Limitation: Not effective for nested lock acquisition
Deadlock Analysis with Thread Dumps
Thread dump = snapshot of thread stack traces
Shows:
Locks held by each thread
Locks awaited
Acquisition locations
Deadlock detection
JVM analyzes “is-waiting-for” graph for cycles
If cycle found, deadlock info is included:
Involved threads
Involved locks
Lock acquisition points
Triggering a thread dump:
Unix: kill -3 (SIGQUIT) or Ctrl-\
Windows: Ctrl-Break
IDEs: Usually provide GUI thread-dump functionality
Java 6 and later:
Includes support for:
Thread dumps with intrinsic and explicit locks
Note: Info about explicit locks less precise
Intrinsic: tied to stack frame
Explicit: tied only to thread