Messages in this thread Patch in this message | | | Date | Sat, 21 Sep 2013 20:34:36 +0200 | From | Oleg Nesterov <> | Subject | Re: [PATCH 1/1] tty: disassociate_ctty() sends the extra SIGCONT |
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Peter, sorry for delay, I was sick.
On 09/17, Peter Hurley wrote: > > On 09/15/2013 11:50 AM, Oleg Nesterov wrote: > >> Put the "!on_exit" check back to restore the old behaviour. >> >> Cc: stable@vger.kernel.org # v3.10+ >> Signed-off-by: Oleg Nesterov <oleg@redhat.com> >> Reported-by: Karel Srot <ksrot@redhat.com> > > Reviewed-by: Peter Hurley <peter@hurleysoftware.com>
Thanks!
Can I ask the question? tty_signal_session_leader() is probably fine, but it _looks_ buggy or at least confusing to me.
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.
Oleg.
--- x/drivers/tty/tty_io.c +++ x/drivers/tty/tty_io.c @@ -548,7 +548,7 @@ static int tty_signal_session_leader(str { struct task_struct *p; int refs = 0; - struct pid *tty_pgrp = NULL; + struct pid *tty_pgrp = tty_get_pgrp(tty); read_lock(&tasklist_lock); if (tty->session) { @@ -560,18 +560,12 @@ static int tty_signal_session_leader(str the tasklist lock */ refs++; } - if (!p->signal->leader) { - spin_unlock_irq(&p->sighand->siglock); - continue; + if (p->signal->leader) { + __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 */ + p->signal->tty_old_pgrp = get_pid(tty_pgrp); } - __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); - if (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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