Re: heavy handed exit() in latest BK

From: Roland McGrath (
Date: Sun Feb 09 2003 - 06:56:50 EST

> - a read_lock(&tasklist_lock) is missing around the group_send_sig_info()
> in send_sig_info().

Indeed. I still intend to clean up those entry points and haven't gotten
to it, so I hadn't bothered with this yet either (though I think I sent it
to you for the backport). It certainly does bite in practice, e.g. SIGPIPE.

There is a similar failure to take the lock before using zap_other_threads.
I thought I sent this patch before, but it's not in 2.5 yet.

--- /home/roland/redhat/linux-2.5.59-1.1007/fs/exec.c.~1~ Fri Feb 7 20:04:27 2003
+++ /home/roland/redhat/linux-2.5.59-1.1007/fs/exec.c Sun Feb 9 03:43:36 2003
@@ -601,9 +601,12 @@ static inline int de_thread(struct task_
         if (thread_group_empty(current))
                 goto no_thread_group;
- * Kill all other threads in the thread group:
+ * Kill all other threads in the thread group.
+ * We must hold tasklist_lock to call zap_other_threads.
+ read_lock(&tasklist_lock);
         if (oldsig->group_exit) {
@@ -611,6 +614,7 @@ static inline int de_thread(struct task_
                  * return so that the signal is processed.
+ read_unlock(&tasklist_lock);
                 kmem_cache_free(sighand_cachep, newsighand);
                 if (newsig)
                         kmem_cache_free(signal_cachep, newsig);
@@ -629,12 +633,15 @@ static inline int de_thread(struct task_
                 oldsig->group_exit_task = current;
                 current->state = TASK_UNINTERRUPTIBLE;
+ read_unlock(&tasklist_lock);
+ read_lock(&tasklist_lock);
                 if (oldsig->group_exit_task)
+ read_unlock(&tasklist_lock);
          * At this point all other threads have exited, all we have to

> - session-IDs and group-IDs are set outside the tasklist lock. This
> causes breakage in the USB code. The correct fix is to do this:

This is outside the part of the code that I've touched lately.

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This archive was generated by hypermail 2b29 : Sat Feb 15 2003 - 22:00:21 EST