What is there to a thread beside a stack

Question

In a Linux process, each thread has its own stack. Besides that, what else is local to each thread. I have read things such as file allocation table, etc... Can someone provide me a list of things which are specific to a thread and how they are arranged in the memory.

Secondly, I have noticed that when I allocate a stack to a thread (See code below), the address of the first variable in the thread function is somehow quite bytes after the stack address which I allocated (stackAddr). I think that is because the top of the stack is the end address of the allocated stack memory, as the difference in value of the address of the local variable and the allocated stack is approximately the size of the stack (STACKSIZE). In other words, it looks like its growing from bottom towards the top.

pthread_attr_init( &attr[tid] );
stackAddr = malloc(STACKSIZE);
pthread_attr_setstack( &attr, stackAddr, STACKSIZE );

Answer 1

For the first question I can think of:

• thread id
• Stack
• machine registers
• threads-specific variables (both key/value pairs set by pthread_setspecific and __thread storage class)
• signal mask
• set of pending signals
• errno value

Second, yes, you are right, on x86 the stack grows to lower addresses. So, if you're using pthread_attr_setstack the area will begin to be used from the end.

Answer 2

Per POSIX XBD 3.396

A single flow of control within a process. Each thread has its own thread ID, scheduling priority and policy, errno value, thread-specific key/value bindings, and the required system resources to support a flow of control. Anything whose address may be determined by a thread, including but not limited to static variables, storage obtained via malloc(), directly addressable storage obtained through implementation-defined functions, and automatic variables, are accessible to all threads in the same process.