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Date: Sun, 9 Feb 2003 12:40:32 +0100 (CET)
From: Ingo Molnar <mingo@elte.hu>
Reply-To: Ingo Molnar <mingo@elte.hu>
To: Roland McGrath <roland@redhat.com>
Cc: Linus Torvalds <torvalds@transmeta.com>, Anton Blanchard <anton@samba.org>,
       Andrew Morton <akpm@digeo.com>, Arjan van de Ven <arjanv@redhat.com>,
       <linux-kernel@vger.kernel.org>
Subject: Re: heavy handed exit() in latest BK
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Roland,

there are two bugs in the signal code still:

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

 - 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:

void __set_special_pids(pid_t session, pid_t pgrp)
{
        struct task_struct *curr = current;

        if (curr->session != session) {
                detach_pid(curr, PIDTYPE_SID);
                curr->session = session;
                attach_pid(curr, PIDTYPE_SID, session);
        }
        if (curr->pgrp != pgrp) {
                detach_pid(curr, PIDTYPE_PGID);
                curr->pgrp = pgrp;
                attach_pid(curr, PIDTYPE_PGID, pgrp);
        }
}

void set_special_pids(pid_t session, pid_t pgrp)
{
        write_lock_irq(&tasklist_lock);
        __set_special_pids(session, pgrp);
        write_unlock_irq(&tasklist_lock);
}

and then update all places that do:

-	current->session = 1;
-	current->pgrp = 1;

to:

+	set_special_pids(1, 1);

otherwise we change the PIDs without properly rehashing them.

	Ingo