Hi Linus,
I've attached a patch to kill all subsidiary threads in a thread group when
the main thread exits. I've made it against 2.5.6-pre3.
Features:
- It sends the subsidiary threads SIGKILL with SI_DETHREAD.
- Subsidiary threads doing an execve() just leave the thread group (rather
than forcing the master thread to do an execve() which would be more POSIX
like).
David
diff -uNr linux-2.5.6-pre3/fs/exec.c linux-execve-256p3/fs/exec.c
--- linux-2.5.6-pre3/fs/exec.c Thu Mar 7 09:08:50 2002
+++ linux-execve-256p3/fs/exec.c Thu Mar 7 09:13:47 2002
@@ -509,23 +509,49 @@
/*
* An execve() will automatically "de-thread" the process.
- * Note: we don't have to hold the tasklist_lock to test
- * whether we migth need to do this. If we're not part of
- * a thread group, there is no way we can become one
- * dynamically. And if we are, we only need to protect the
- * unlink - even if we race with the last other thread exit,
- * at worst the list_del_init() might end up being a no-op.
+ * - if a master thread (PID==TGID) is doing this, then all subsidiary threads
+ * will be killed (otherwise there will end up being two independent thread
+ * groups with the same TGID).
+ * - if a subsidary thread is doing this, then it just leaves the thread group
*/
-static inline void de_thread(struct task_struct *tsk)
+static void de_thread(struct task_struct *tsk)
{
- if (!list_empty(&tsk->thread_group)) {
- write_lock_irq(&tasklist_lock);
+ struct task_struct *sub;
+ struct list_head *head, *ptr;
+ struct siginfo info;
+ int pause;
+
+ write_lock_irq(&tasklist_lock);
+
+ if (tsk->tgid != tsk->pid) {
+ /* subsidiary thread - just escapes the group */
+ list_del_init(&tsk->thread_group);
+ tsk->tgid = tsk->pid;
+ pause = 0;
+ }
+ else {
+ /* master thread - kill all subsidiary threads */
+ info.si_signo = SIGKILL;
+ info.si_errno = 0;
+ info.si_code = SI_DETHREAD;
+ info.si_pid = current->pid;
+ info.si_uid = current->uid;
+
+ head = tsk->thread_group.next;
list_del_init(&tsk->thread_group);
- write_unlock_irq(&tasklist_lock);
+
+ list_for_each(ptr,head) {
+ sub = list_entry(ptr,struct task_struct,thread_group);
+ send_sig_info(SIGKILL,&info,sub);
+ }
+
+ pause = 1;
}
- /* Minor oddity: this might stay the same. */
- tsk->tgid = tsk->pid;
+ write_unlock_irq(&tasklist_lock);
+
+ /* give the subsidiary threads a chance to clean themselves up */
+ if (pause) yield();
}
int flush_old_exec(struct linux_binprm * bprm)
@@ -566,7 +592,8 @@
flush_thread();
- de_thread(current);
+ if (!list_empty(¤t->thread_group))
+ de_thread(current);
if (bprm->e_uid != current->euid || bprm->e_gid != current->egid ||
permission(bprm->file->f_dentry->d_inode,MAY_READ))
diff -uNr linux-2.5.6-pre3/include/asm-i386/siginfo.h linux-execve-256p3/include/asm-i386/siginfo.h
--- linux-2.5.6-pre3/include/asm-i386/siginfo.h Thu Mar 7 09:07:06 2002
+++ linux-execve-256p3/include/asm-i386/siginfo.h Thu Mar 7 09:17:53 2002
@@ -108,6 +108,7 @@
#define SI_ASYNCIO -4 /* sent by AIO completion */
#define SI_SIGIO -5 /* sent by queued SIGIO */
#define SI_TKILL -6 /* sent by tkill system call */
+#define SI_DETHREAD -7 /* sent by execve() killing subsidiary threads */
#define SI_FROMUSER(siptr) ((siptr)->si_code <= 0)
#define SI_FROMKERNEL(siptr) ((siptr)->si_code > 0)
-
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This archive was generated by hypermail 2b29 : Thu Mar 07 2002 - 21:01:01 EST