Messages in this thread | | | Date | Tue, 5 Sep 2006 19:19:42 -0400 | From | Alan Cox <> | Subject | Re: + audit-accounting-tty-locking.patch added to -mm tree |
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On Wed, Sep 06, 2006 at 03:07:53AM +0400, Oleg Nesterov wrote: > Nowadays ->signal/->sighand are _also_ protected by ->sighand->siglock. > Unless you are current, you can't lock ->siglock directly (without holding > tasklist_lock), you should use lock_task_sighand().
Gack, that makes current controlling tty locking horrible (and wrong almost everywhere still across a clone)
> tty_io.c: > ->tty is set under task_lock() > > ->tty is cleared under lock_kernel() + tasklist_lock > > except TIOCNOTTY, cleared under task_lock() > > Note that include/linux/sched.h doesn't document that ->alloc_lock > protects ->tty, it is only used in tty_io.c for that purpose, why?
Work in progress
> Btw, I think tiocsctty()/tty_open() is racy wrt to sys_setsid(). > tiocsctty() can see the result of '->signal->leader = 1' before > sys_setsid() changed ->session/->pgrp and passed '->tty = NULL'.
Correct. I'm doing them bit by bit as I unpick them and check they don't deadlock. If we need to take task_lock as well then its time for set_controlling_tty() to get added.
Thanks for the signal lock explanation though. Now I've more idea wtf is going on below the tty layer
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