Thread

OS allocates resources to process.

• Process: management unit
• Thread: execution unit included in a process

Context

• Each thread has its own context
  • TLS
  • Stack
  • Register set4

Shared resource

• Threads in a process share its resources
  • Heap, Data, File, etc…

→ Shared resources cause race condition

→ Synchronization is required

Overhead

• Context switching
• Synchronization → deadlock
• Cache miss
• Thread creation
• Scheduling

Synchronization

• Critical Section: Resource that more than one threads access

• Synchronization Object

  • User level - critical section
  • Kernel level - mutex, semaphore

• Deadlock

  • Thread1 locks resource1 and tries to get resource2
  • Thread2 locks resource2 and tries to get resource1
  • Both Thread1 and Thread2 do nothing but to wait for each locked resource

  

  Event-loop

  

  1. InputThread pushes an event

  2. UIThread pops out

  3. UIThread creates a thread that will handle the event

  4. UIThread can keep reacting to another event almost immediately

     obj.compare_exchange(expected, desired);
     
     if (obj == expected){
     	obj = desired;
     	return true;	
     }
     
     expected = desired;
     return false;