From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Message-ID: <4F37B34F.1040307@suse.cz> Date: Sun, 12 Feb 2012 13:40:47 +0100 From: Jiri Slaby MIME-Version: 1.0 References: <1329006070-4275-1-git-send-email-richard@nod.at> <20120212010211.GN23916@ZenIV.linux.org.uk> In-Reply-To: <20120212010211.GN23916@ZenIV.linux.org.uk> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Subject: Re: your mail To: Al Viro Cc: Richard Weinberger , linux-kernel@vger.kernel.org, user-mode-linux-devel@lists.sourceforge.net, akpm@linux-foundation.org, alan@lxorguk.ukuu.org.uk, gregkh@linuxfoundation.org, Jiri Slaby List-ID: On 02/12/2012 02:02 AM, Al Viro wrote: > On Sun, Feb 12, 2012 at 01:21:10AM +0100, Richard Weinberger wrote: >> +++ b/arch/um/drivers/line.c >> @@ -19,19 +19,29 @@ static irqreturn_t line_interrupt(int irq, void *data) >> { >> struct chan *chan = data; >> struct line *line = chan->line; >> + struct tty_struct *tty; >> + >> + if (line) { >> + tty = tty_port_tty_get(&line->port); >> + chan_interrupt(&line->chan_list, &line->task, tty, irq); >> + tty_kref_put(tty); >> + } >> >> - if (line) >> - chan_interrupt(&line->chan_list, &line->task, line->tty, irq); >> return IRQ_HANDLED; >> } > > Is tty_kref_put() safe in interrupt? Here it seems to be OK, but in other > callers... More or less at random: drivers/tty/serial/lantiq.c has it > called from lqasc_rx_int(). It seems to be possible to have it end up > calling ->ops->shutdown() and in this case that'd be lqasc_shutdown(). > Which does a bunch of free_irq(), including the ->rx_irq, i.e. the one > we have it called from. Alan? I'm not Alan, but will reply anyway. Yes, it is safe (unless the driver does something tricky). In the driver you mention, this is uart_ops, called from tty_port_operations' ->shutdown. And that's a different from tty_operations' ->shutdown. Yes, there are: * tty->ops * tty_port->ops * uart_port->ops uart_port->ops->shutdown is supposed to tear down interrupts like in lantiq.c. It is called from tty_port->ops->shutdown. And that one is allowed to be called only from user context (tty->ops->close and tty->ops->hangup). thanks, -- js suse labs