dynamic thread creation is expensive
Dynamic decision
– if handler doesn’t lock => execute on interrupted threads stack
– if handler can block => turn into real thread
Optimization
– precreate z prenitialize thread structures for interrupt routines
Threads and Signal Handling
– disable => clear signal
– signal occurs – what to do with the signal?
SIGNAL-N, handler-N-start-addr
user, kernel mask
Optimize Common Case
– signals less frequent than signal mask updates
– system calls avoided cheaper to update UL mask
Task struct in Linux
– main execution abstraction => task
Struct task_struct {
// ...
pid_t pid;
pid_t tgid;
int prio;
volatile long state;
struct mm_struct **mm;
struct files_struct *files;
struct list_head tasks;
int on_cpu;
cpumask_t cpus_allowed;
// ...
}
