THE ABCS OF THREAD SAFETY郑宜霖

0 THREAD

0.0 WHAT ARE THREADS

0.1 WHY THREADS

1 THREAD “UNSAFETY”

1.0 RACE CONDITION

1.1 CASE I: READ-INCREASE-WRITE

1.2 CASE II: REMOVING A NODE

2 MUTEX

2.0 MUTUAL EXCLUSION

2.1 INCREMENT-MUTEX

2.2 SOUNDS GOOD?

•Hardware Interrupt

•Signal

2.3 REENTRANCY 

Lock the Mutex

Interrupt Call increment()

Unable to LockSome Operations

Unlock the Mutex

3 ATOMIC OPERATION

3.0 ATOMIC OPERATIONS

3.1 INCREMENT-ATOMIC

3.2 STD::ATOMIC

3.3 HOW DO THEY DO IT?

• Hardware Support for Atomic Operations (adding, incrementing, subtracting, etc.)

• Support for CAS (hardware / software)

3.4 COMPARE-AND-SWAP

3.5 INCREMENT-CAS

3.6 WHAT’S MORE

•Only CAS with 1, 2 ,4 ,8 Bytes

•How to implement an atomic class?

REFERENCES

• GStreamer Application Development Manual

• Wikipedia

• Cppreference

• GCC Wiki

THANKS