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Threads

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A thread is a struct proc that shares three counted objects with others of
its group: the address space (struct mm: page tables, heap top, VMAs and a
lock for changing them), the descriptor table, and the signal dispositions.
clone() shares what its flags say and fork() copies.

- clone(): pthread_create's shape (VM, FILES, SIGHAND, THREAD, SETTLS,
  PARENT_SETTID, CHILD_CLEARTID) and posix_spawn's (VM, VFORK, a stack).
- futex: WAIT, WAIT_BITSET with timeouts, WAKE, REQUEUE, CMP_REQUEUE, keyed
  by the word's kernel address so shared pages meet. set_tid_address keeps
  the word that exit zeroes and wakes, for pthread_join.
- exit ends a thread; exit_group, a fatal signal, or the leader exiting ends
  them all. reapd frees exited threads; the leader is reaped by its parent
  once the rest are gone. getpid is the group, gettid the thread.
- Stops and resumes reach every thread; other process signals the leader.
- exec kills the other threads and unshares the dispositions.
- No TLB shootdown, so pages unmapped from a shared address space are freed
  only once every CPU has reloaded CR3 or is idle.
- procfs: /proc lists processes, task/ lists threads, comm, Threads:, Tgid.
- The console honours VMIN 0 / VTIME (btop's input drain hung on it).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01S1giNvrHTrPMPw7V6x1kQ4
This commit is contained in:
Nexoniarz 2026-10-25 03:03:50 +01:00
commit f4d7f9100d
19 changed files with 1300 additions and 248 deletions
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12
kernel/sys/sys_event.c
View file

@ -143,7 +143,7 @@ ev_open(struct evobj *o, int flags, int readable, int writable)
return -EMFILE;
}
if (flags & O_CLOEXEC)
myproc()->ofile_flags[fd] |= FD_CLOEXEC;
myproc()->files->flags[fd] |= FD_CLOEXEC;
return fd;
}
@ -163,7 +163,7 @@ ev_arg(int n, int kind, struct file **pf)
{
int fd;
struct file *f;
if (argint(n, &fd) < 0 || fd < 0 || fd >= NOFILE || !(f = myproc()->ofile[fd]))
if (argint(n, &fd) < 0 || fd < 0 || fd >= NOFILE || !(f = myproc()->files->ofile[fd]))
return 0;
if (f->type != FD_EVENT || f->ev->kind != kind)
return 0;
@ -497,7 +497,7 @@ signalfd_common(int fd, addr_t umask, uint64 size, int flags)
// An existing signalfd: change its mask, keep the descriptor.
if (fd != -1) {
struct file *f;
if (fd < 0 || fd >= NOFILE || !(f = myproc()->ofile[fd]) ||
if (fd < 0 || fd >= NOFILE || !(f = myproc()->files->ofile[fd]) ||
f->type != FD_EVENT || f->ev->kind != EV_SIGNALFD)
return -EINVAL;
acquiresleep(&f->ev->lock);
@ -606,9 +606,9 @@ sys_epoll_ctl(void)
return -EBADF;
if (argint(1, &op) < 0 || argint(2, &fd) < 0 || argaddr(3, &uev) < 0)
return -EINVAL;
if (fd < 0 || fd >= NOFILE || !myproc()->ofile[fd])
if (fd < 0 || fd >= NOFILE || !myproc()->files->ofile[fd])
return -EBADF;
struct file *tf = myproc()->ofile[fd];
struct file *tf = myproc()->files->ofile[fd];
// A set cannot watch itself. (Nor contain a set that contains it; that
// check is the deep one Linux does, and nothing here builds such loops.)
if (tf == ef)
@ -662,7 +662,7 @@ ep_ready(struct evobj *o, struct epoll_event *out, int max)
acquiresleep(&o->lock);
for (int i = 0; i < o->ep.n && got < max; ) {
struct epitem *it = &o->ep.items[i];
struct file *now = (it->fd >= 0 && it->fd < NOFILE) ? myproc()->ofile[it->fd] : 0;
struct file *now = (it->fd >= 0 && it->fd < NOFILE) ? myproc()->files->ofile[it->fd] : 0;
if (now != it->f) {
ep_drop(o, i); // closed: it leaves the set
continue;