Messages in this thread Patch in this message | | | Date | Sun, 22 Sep 2013 22:03:54 +0200 | From | Oleg Nesterov <> | Subject | Re: [PATCH 1/1] tty: disassociate_ctty() sends the extra SIGCONT |
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On 09/21, Peter Hurley wrote: > > On 09/21/2013 02:34 PM, Oleg Nesterov wrote: >> >> do_each_pid_task(tty->session, PIDTYPE_SID, p) { >> spin_lock_irq(&p->sighand->siglock); >> if (p->signal->tty == tty) { >> p->signal->tty = NULL; >> /* We defer the dereferences outside fo >> the tasklist lock */ >> refs++; >> } >> if (!p->signal->leader) { >> spin_unlock_irq(&p->sighand->siglock); >> continue; >> } >> __group_send_sig_info(SIGHUP, SEND_SIG_PRIV, p); >> __group_send_sig_info(SIGCONT, SEND_SIG_PRIV, p); >> put_pid(p->signal->tty_old_pgrp); /* A noop */ >> spin_lock(&tty->ctrl_lock); >> tty_pgrp = get_pid(tty->pgrp); >> >> I guess this can happen only once, so we could even add WARN_ON(tty_pgrp) >> before get_pid(). But this look confusing, as if we can do get_pid() >> multiple times and leak tty->pgrp. >> >> if (tty->pgrp) >> p->signal->tty_old_pgrp = get_pid(tty->pgrp); >> >> else? We already did put_pid(tty_old_pgrp), we should clear it. >> >> IOW, do you think the patch below makes sense or I missed something? >> Just curious. > > The code block you're referring to only executes once because there is > only one session leader.
I understand, and I even mentioned this above.
My point was, this _looks_ confusing, and the patch I sent makes it more clean.
And what about ->tty_old_pgrp? I still think that at least the patch below makes sense. If tty->pgrp == NULL is not possible here (I do not know), then why do we check? Otherwise ->tty_old_pgrp != NULL looks certainly wrong after put_pid().
Oleg.
--- x/drivers/tty/tty_io.c +++ x/drivers/tty/tty_io.c @@ -569,8 +569,7 @@ static int tty_signal_session_leader(str put_pid(p->signal->tty_old_pgrp); /* A noop */ spin_lock(&tty->ctrl_lock); tty_pgrp = get_pid(tty->pgrp); - if (tty->pgrp) - p->signal->tty_old_pgrp = get_pid(tty->pgrp); + p->signal->tty_old_pgrp = get_pid(tty->pgrp); spin_unlock(&tty->ctrl_lock); spin_unlock_irq(&p->sighand->siglock); } while_each_pid_task(tty->session, PIDTYPE_SID, p);
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