From: Peter Hurley <peter@hurleysoftware.com>
To: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Jiri Slaby <jslaby@suse.cz>,
linux-kernel@vger.kernel.org, linux-serial@vger.kernel.org,
One Thousand Gnomes <gnomes@lxorguk.ukuu.org.uk>,
Peter Hurley <peter@hurleysoftware.com>
Subject: [PATCH -next 5/9] pty: Don't claim slave's ctrl_lock for master's packet mode
Date: Thu, 16 Oct 2014 15:33:26 -0400 [thread overview]
Message-ID: <1413488010-16885-6-git-send-email-peter@hurleysoftware.com> (raw)
In-Reply-To: <1413488010-16885-1-git-send-email-peter@hurleysoftware.com>
The slave's ctrl_lock serializes updates to the ctrl_status field
only, whereas the master's ctrl_lock serializes updates to the
packet mode enable (ie., the master does not have ctrl_status and
the slave does not have packet mode). Thus, claiming the slave's
ctrl_lock to access ->packet is useless.
Unlocked reads of ->packet are already smp-safe.
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
---
drivers/tty/n_tty.c | 4 ++--
drivers/tty/pty.c | 8 ++++----
2 files changed, 6 insertions(+), 6 deletions(-)
diff --git a/drivers/tty/n_tty.c b/drivers/tty/n_tty.c
index 53cdfbe..6a42204 100644
--- a/drivers/tty/n_tty.c
+++ b/drivers/tty/n_tty.c
@@ -351,13 +351,13 @@ static void n_tty_packet_mode_flush(struct tty_struct *tty)
{
unsigned long flags;
- spin_lock_irqsave(&tty->ctrl_lock, flags);
if (tty->link->packet) {
+ spin_lock_irqsave(&tty->ctrl_lock, flags);
tty->ctrl_status |= TIOCPKT_FLUSHREAD;
+ spin_unlock_irqrestore(&tty->ctrl_lock, flags);
if (waitqueue_active(&tty->link->read_wait))
wake_up_interruptible(&tty->link->read_wait);
}
- spin_unlock_irqrestore(&tty->ctrl_lock, flags);
}
/**
diff --git a/drivers/tty/pty.c b/drivers/tty/pty.c
index 29b5eeb..e554393 100644
--- a/drivers/tty/pty.c
+++ b/drivers/tty/pty.c
@@ -339,26 +339,26 @@ static void pty_start(struct tty_struct *tty)
{
unsigned long flags;
- spin_lock_irqsave(&tty->ctrl_lock, flags);
if (tty->link && tty->link->packet) {
+ spin_lock_irqsave(&tty->ctrl_lock, flags);
tty->ctrl_status &= ~TIOCPKT_STOP;
tty->ctrl_status |= TIOCPKT_START;
+ spin_unlock_irqrestore(&tty->ctrl_lock, flags);
wake_up_interruptible_poll(&tty->link->read_wait, POLLIN);
}
- spin_unlock_irqrestore(&tty->ctrl_lock, flags);
}
static void pty_stop(struct tty_struct *tty)
{
unsigned long flags;
- spin_lock_irqsave(&tty->ctrl_lock, flags);
if (tty->link && tty->link->packet) {
+ spin_lock_irqsave(&tty->ctrl_lock, flags);
tty->ctrl_status &= ~TIOCPKT_START;
tty->ctrl_status |= TIOCPKT_STOP;
+ spin_unlock_irqrestore(&tty->ctrl_lock, flags);
wake_up_interruptible_poll(&tty->link->read_wait, POLLIN);
}
- spin_unlock_irqrestore(&tty->ctrl_lock, flags);
}
/**
--
2.1.1
next prev parent reply other threads:[~2014-10-16 19:33 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-10-16 19:33 [PATCH -next 0/9] pty fixes Peter Hurley
2014-10-16 19:33 ` [PATCH -next 1/9] tty: WARN for attempted set_termios() of pty master Peter Hurley
2014-10-16 19:33 ` [PATCH -next 2/9] tty: Move pty-specific set_termios() handling to pty driver Peter Hurley
2014-10-16 19:33 ` [PATCH -next 3/9] pty: Use spin_lock_irq() for pty_set_termios() Peter Hurley
2014-10-16 19:33 ` [PATCH -next 4/9] tty: Use spin_lock_irq() for ctrl_lock when interrupts enabled Peter Hurley
2014-10-16 19:33 ` Peter Hurley [this message]
2014-10-16 19:33 ` [PATCH -next 6/9] pty: Fix packet mode setting race Peter Hurley
2014-10-16 19:33 ` [PATCH -next 7/9] pty: Hold ctrl_lock for packet mode updates Peter Hurley
2014-10-16 19:33 ` [PATCH -next 8/9] tty: Fix missed wakeup from packet mode status update Peter Hurley
2014-10-16 19:33 ` [PATCH -next 9/9] n_tty: Only process packet mode data in raw mode Peter Hurley
2014-10-22 15:37 ` [PATCH -next 0/9] pty fixes One Thousand Gnomes
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