Thread life cycle

The number of threads within a process can vary widely, with threads being created and destroyed dynamically.

Thread creation (pthread_create() ) involves allocating and initializing the necessary resources within the process's address space (e.g. thread stack) and starting the execution of the thread at some function in the address space.

Thread termination (pthread_exit() , pthread_cancel() ) involves stopping the thread and reclaiming the thread's resources. As a thread executes, its state can generally be described as either ready or blocked. More specifically, it can be one of the following:

Figure showing possible thread states.
CONDVAR
The thread is blocked on a condition variable (e.g. it called pthread_cond_wait() ).
DEAD
The thread has terminated and is waiting for a join by another thread.
INTERRUPT
The thread is blocked waiting for an interrupt (i.e. it called InterruptWait() ).
JOIN
The thread is blocked waiting to join another thread (e.g. it called pthread_join() ).
MUTEX
The thread is blocked on a mutual exclusion lock (e.g. it called pthread_mutex_lock() ).
NANOSLEEP
The thread is sleeping for a short time interval (e.g. it called nanosleep() ).
NET_REPLY
The thread is waiting for a reply to be delivered across the network (i.e. it called MsgReply*() ).
NET_SEND
The thread is waiting for a pulse or signal to be delivered across the network (i.e. it called MsgSendPulse() , MsgDeliverEvent() , or SignalKill() ).
READY
The thread is waiting to be executed while the processor executes another thread of equal or higher priority.
RECEIVE
The thread is blocked on a message receive (e.g. it called MsgReceive() ).
REPLY
The thread is blocked on a message reply (i.e. it called MsgSend() , and the server received the message).
RUNNING
The thread is being executed by a processor. The kernel uses an array (with one entry per processor in the system) to keep track of the running threads.
SEM
The thread is waiting for a semaphore to be posted (i.e. it called SyncSemWait() ).
SEND
The thread is blocked on a message send (e.g. it called MsgSend() , but the server hasn't yet received the message).
SIGSUSPEND
The thread is blocked waiting for a signal (i.e. it called sigsuspend() ).
SIGWAITINFO
The thread is blocked waiting for a signal (i.e. it called sigwaitinfo() ).
STACK
The thread is waiting for the virtual address space to be allocated for the thread's stack (parent will have called ThreadCreate() ).
STOPPED
The thread is blocked waiting for a SIGCONT signal.
WAITCTX
The thread is waiting for a noninteger (e.g. floating point) context to become available for use.
WAITPAGE
The thread is waiting for physical memory to be allocated for a virtual address.
WAITTHREAD
The thread is waiting for a child thread to finish creating itself (i.e. it called ThreadCreate() ).