What are common mistakes developers make with deadlocks and livelocks?

Deadlocks and livelocks are common concurrency issues faced by developers. Here are some common mistakes that can lead to these problems:

  • Ignoring Lock Ordering: Developers often fail to acquire locks in a consistent order, which can lead to deadlocks.
  • Holding Multiple Locks: Holding more than one lock can increase the chances of a deadlock occurring.
  • Not Using Timeout: Failing to set timeouts can lead to processes waiting indefinitely, resulting in a deadlock situation.
  • Poor Exception Handling: Developers often overlook handling exceptions that occur during lock acquisition, which can leave resources locked.
  • Underestimating Resource Contention: Not analyzing resource contention can lead to livelocks when multiple threads keep changing their state in response to each other.

By understanding these common mistakes, developers can implement better patterns to prevent deadlocks and livelocks in their applications.

// Example demonstrating a potential deadlock situation class Foo { public function method1($lock1, $lock2) { $lock1->acquire(); sleep(1); // Simulate some work $lock2->acquire(); // Could cause a deadlock if another process has $lock2 $lock2->release(); $lock1->release(); } public function method2($lock2, $lock1) { $lock2->acquire(); sleep(1); // Simulate some work $lock1->acquire(); // Could cause a deadlock if another process has $lock1 $lock1->release(); $lock2->release(); } }

deadlocks livelocks concurrency issues lock ordering exception handling

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