From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756567AbZELWdJ (ORCPT ); Tue, 12 May 2009 18:33:09 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753163AbZELWch (ORCPT ); Tue, 12 May 2009 18:32:37 -0400 Received: from mail.windriver.com ([147.11.1.11]:57580 "EHLO mail.wrs.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752271AbZELWcf (ORCPT ); Tue, 12 May 2009 18:32:35 -0400 From: Jason Wessel To: greg@kroah.com Cc: linux-usb@vger.kernel.org, oliver@neukum.org, stern@rowland.harvard.edu, linux-kernel@vger.kernel.org, Jason Wessel Subject: [PATCH 2/2] usb_serial: Run the sysrq handler in a tasklet Date: Tue, 12 May 2009 17:32:20 -0500 Message-Id: <1242167540-23585-3-git-send-email-jason.wessel@windriver.com> X-Mailer: git-send-email 1.6.3.9.g6345d In-Reply-To: <1242167540-23585-2-git-send-email-jason.wessel@windriver.com> References: <1242167540-23585-1-git-send-email-jason.wessel@windriver.com> <1242167540-23585-2-git-send-email-jason.wessel@windriver.com> X-OriginalArrivalTime: 12 May 2009 22:32:25.0346 (UTC) FILETIME=[8629AE20:01C9D351] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org If a sysrq is processed on the while holding the usb hcd lock, it is impossible to drain the queue of urbs via the polling interface and all the printk output is lost. Using a tasklet to schedule the sysrq allows the hcd device lock to free up. Signed-off-by: Jason Wessel --- drivers/usb/serial/generic.c | 33 ++++++++++++++++++++++++++++++++- 1 files changed, 32 insertions(+), 1 deletions(-) diff --git a/drivers/usb/serial/generic.c b/drivers/usb/serial/generic.c index df56ed3..7554d71 100644 --- a/drivers/usb/serial/generic.c +++ b/drivers/usb/serial/generic.c @@ -527,11 +527,42 @@ void usb_serial_generic_unthrottle(struct tty_struct *tty) } } +#ifdef CONFIG_MAGIC_SYSRQ +/* The sysrq tasklet is used to make the sysrq request not occur with + * the hcd device lock held. + */ +static struct usb_sysrq_data { + struct tty_struct *tty; + unsigned int ch; + int pending; +} priv_usb_sysrq; + +static void usb_sysrq_task(unsigned long args) +{ + handle_sysrq(priv_usb_sysrq.ch, priv_usb_sysrq.tty); + priv_usb_sysrq.pending = 0; +} +static DECLARE_TASKLET(usb_sysrq_tasklet, usb_sysrq_task, 0); + +void usb_serial_generic_sysrq_invoke(struct usb_serial_port *port, + unsigned int ch) +{ + if (priv_usb_sysrq.pending) + return; + priv_usb_sysrq.pending = 1; + priv_usb_sysrq.ch = ch; + priv_usb_sysrq.tty = tty_port_tty_get(&port->port); + tasklet_schedule(&usb_sysrq_tasklet); +} +#else +static void usb_serial_generic_sysrq_invoke() {} +#endif /* CONFIG_SYSRQ */ + int usb_serial_handle_sysrq_char(struct usb_serial_port *port, unsigned int ch) { if (port->sysrq) { if (ch && time_before(jiffies, port->sysrq)) { - handle_sysrq(ch, tty_port_tty_get(&port->port)); + usb_serial_generic_sysrq_invoke(port, ch); port->sysrq = 0; return 1; } -- 1.6.3.9.g6345d