From mboxrd@z Thu Jan 1 00:00:00 1970 From: Peter Hurley Subject: [PATCH 3/4] net/irda: Use barrier to set task state Date: Tue, 5 Mar 2013 11:09:06 -0500 Message-ID: <1362499747-4262-4-git-send-email-peter@hurleysoftware.com> References: <1362371063.3221.185.camel@thor.lan> <1362499747-4262-1-git-send-email-peter@hurleysoftware.com> Cc: Sasha Levin , Greg Kroah-Hartman , netdev@vger.kernel.org, Jiri Slaby , linux-kernel@vger.kernel.org, Peter Hurley To: David Miller , Samuel Ortiz Return-path: In-Reply-To: <1362499747-4262-1-git-send-email-peter@hurleysoftware.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org Without a memory and compiler barrier, the task state change can migrate relative to the condition testing in a blocking loop. However, the task state change must be visible across all cpus prior to testing those conditions. Failing to do this can result in the familiar 'lost wakeup' and this task will hang until killed. Signed-off-by: Peter Hurley --- net/irda/ircomm/ircomm_tty.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/net/irda/ircomm/ircomm_tty.c b/net/irda/ircomm/ircomm_tty.c index d282bbe..522543d 100644 --- a/net/irda/ircomm/ircomm_tty.c +++ b/net/irda/ircomm/ircomm_tty.c @@ -324,7 +324,7 @@ static int ircomm_tty_block_til_ready(struct ircomm_tty_cb *self, if (tty->termios.c_cflag & CBAUD) tty_port_raise_dtr_rts(port); - current->state = TASK_INTERRUPTIBLE; + set_current_state(TASK_INTERRUPTIBLE); if (tty_hung_up_p(filp) || !test_bit(ASYNCB_INITIALIZED, &port->flags)) { -- 1.8.1.2