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Message-Id: <1402924639-5164-10-git-send-email-peter@hurleysoftware.com>
Date: Mon, 16 Jun 2014 09:17:06 -0400
From: Peter Hurley <peter@...leysoftware.com>
To: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: linux-serial@...r.kernel.org, linux-kernel@...r.kernel.org,
One Thousand Gnomes <gnomes@...rguk.ukuu.org.uk>,
Peter Hurley <peter@...leysoftware.com>,
Mikael Starvik <starvik@...s.com>,
Jesper Nilsson <jesper.nilsson@...s.com>,
Samuel Ortiz <samuel@...tiz.org>,
"David S. Miller" <davem@...emloft.net>
Subject: [PATCH tty-next 09/22] tty: Remove tty_hung_up_p() tests from tty drivers' open()
Since at least before 2.6.30, it has not been possible to observe
a hung up file pointer in a tty driver's open() method unless/until
the driver open() releases the tty_lock() (eg., before blocking).
This is because tty_open() adds the file pointer while holding
the tty_lock() _and_ doesn't release the lock until after calling
the tty driver's open() method. [ Before tty_lock(), this was
lock_kernel(). ]
Since __tty_hangup() first waits on the tty_lock() before
enumerating and hanging up the open file pointers, either
__tty_hangup() will wait for the tty_lock() or tty_open() will
not yet have added the file pointer. For example,
CPU 0 | CPU 1
|
tty_open | __tty_hangup
.. | ..
tty_lock | ..
tty_reopen | tty_lock / blocks
.. |
tty_add_file(tty, filp) |
.. |
tty->ops->open(tty, filp) |
tty_port_open |
tty_port_block_til_ready |
.. |
while (1) |
.. |
tty_unlock | / unblocks
schedule | for each filp on tty->tty_files
| f_ops = tty_hung_up_fops;
| ..
| tty_unlock
tty_lock |
.. |
tty_unlock |
Note that since tty_port_block_til_ready() and similar drop
the tty_lock while blocking, when woken, the file pointer
must then be tested for having been hung up.
Also, fix bit-rotted drivers that used extra_count to track the
port->count bump.
CC: Mikael Starvik <starvik@...s.com>
CC: Jesper Nilsson <jesper.nilsson@...s.com>
CC: Samuel Ortiz <samuel@...tiz.org>
CC: "David S. Miller" <davem@...emloft.net>
Signed-off-by: Peter Hurley <peter@...leysoftware.com>
---
drivers/char/pcmcia/synclink_cs.c | 2 +-
drivers/staging/dgrp/dgrp_tty.c | 10 ----------
drivers/tty/cyclades.c | 2 +-
drivers/tty/serial/crisv10.c | 15 +++++----------
drivers/tty/serial/serial_core.c | 8 --------
drivers/tty/synclink.c | 10 +++-------
drivers/tty/synclink_gt.c | 10 +++-------
drivers/tty/synclinkmp.c | 11 +++--------
drivers/tty/tty_port.c | 8 +++-----
net/irda/ircomm/ircomm_tty.c | 6 ++----
10 files changed, 21 insertions(+), 61 deletions(-)
diff --git a/drivers/char/pcmcia/synclink_cs.c b/drivers/char/pcmcia/synclink_cs.c
index 8320abd..a63970f 100644
--- a/drivers/char/pcmcia/synclink_cs.c
+++ b/drivers/char/pcmcia/synclink_cs.c
@@ -2510,7 +2510,7 @@ static int mgslpc_open(struct tty_struct *tty, struct file * filp)
__FILE__, __LINE__, tty->driver->name, port->count);
/* If port is closing, signal caller to try again */
- if (tty_hung_up_p(filp) || port->flags & ASYNC_CLOSING){
+ if (port->flags & ASYNC_CLOSING){
wait_event_interruptible_tty(tty, port->close_wait,
!(port->flags & ASYNC_CLOSING));
retval = ((port->flags & ASYNC_HUP_NOTIFY) ?
diff --git a/drivers/staging/dgrp/dgrp_tty.c b/drivers/staging/dgrp/dgrp_tty.c
index 30d2602..cdd1a69 100644
--- a/drivers/staging/dgrp/dgrp_tty.c
+++ b/drivers/staging/dgrp/dgrp_tty.c
@@ -632,16 +632,6 @@ static int dgrp_tty_open(struct tty_struct *tty, struct file *file)
tty->driver_data = un;
/*
- * If we are in the middle of hanging up,
- * then return an error
- */
- if (tty_hung_up_p(file)) {
- retval = ((un->un_flag & UN_HUP_NOTIFY) ?
- -EAGAIN : -ERESTARTSYS);
- goto done;
- }
-
- /*
* If the port is in the middle of closing, then block
* until it is done, then try again.
*/
diff --git a/drivers/tty/cyclades.c b/drivers/tty/cyclades.c
index a57bb5a..fd66f57 100644
--- a/drivers/tty/cyclades.c
+++ b/drivers/tty/cyclades.c
@@ -1579,7 +1579,7 @@ static int cy_open(struct tty_struct *tty, struct file *filp)
/*
* If the port is the middle of closing, bail out now
*/
- if (tty_hung_up_p(filp) || (info->port.flags & ASYNC_CLOSING)) {
+ if (info->port.flags & ASYNC_CLOSING) {
wait_event_interruptible_tty(tty, info->port.close_wait,
!(info->port.flags & ASYNC_CLOSING));
return (info->port.flags & ASYNC_HUP_NOTIFY) ? -EAGAIN: -ERESTARTSYS;
diff --git a/drivers/tty/serial/crisv10.c b/drivers/tty/serial/crisv10.c
index d567ac5..58e6f61 100644
--- a/drivers/tty/serial/crisv10.c
+++ b/drivers/tty/serial/crisv10.c
@@ -3831,14 +3831,13 @@ block_til_ready(struct tty_struct *tty, struct file * filp,
DECLARE_WAITQUEUE(wait, current);
unsigned long flags;
int retval;
- int do_clocal = 0, extra_count = 0;
+ int do_clocal = 0;
/*
* If the device is in the middle of being closed, then block
* until it's done, and then try again.
*/
- if (tty_hung_up_p(filp) ||
- (info->port.flags & ASYNC_CLOSING)) {
+ if (info->port.flags & ASYNC_CLOSING) {
wait_event_interruptible_tty(tty, info->port.close_wait,
!(info->port.flags & ASYNC_CLOSING));
#ifdef SERIAL_DO_RESTART
@@ -3879,10 +3878,7 @@ block_til_ready(struct tty_struct *tty, struct file * filp,
info->line, info->port.count);
#endif
local_irq_save(flags);
- if (!tty_hung_up_p(filp)) {
- extra_count++;
- info->port.count--;
- }
+ info->port.count--;
local_irq_restore(flags);
info->port.blocked_open++;
while (1) {
@@ -3921,7 +3917,7 @@ block_til_ready(struct tty_struct *tty, struct file * filp,
}
set_current_state(TASK_RUNNING);
remove_wait_queue(&info->port.open_wait, &wait);
- if (extra_count)
+ if (!tty_hung_up_p(filp))
info->port.count++;
info->port.blocked_open--;
#ifdef SERIAL_DEBUG_OPEN
@@ -3976,8 +3972,7 @@ rs_open(struct tty_struct *tty, struct file * filp)
/*
* If the port is in the middle of closing, bail out now
*/
- if (tty_hung_up_p(filp) ||
- (info->port.flags & ASYNC_CLOSING)) {
+ if (info->port.flags & ASYNC_CLOSING) {
wait_event_interruptible_tty(tty, info->port.close_wait,
!(info->port.flags & ASYNC_CLOSING));
#ifdef SERIAL_DO_RESTART
diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c
index f2febb4..c8879ce 100644
--- a/drivers/tty/serial/serial_core.c
+++ b/drivers/tty/serial/serial_core.c
@@ -1572,14 +1572,6 @@ static int uart_open(struct tty_struct *tty, struct file *filp)
tty_port_tty_set(port, tty);
/*
- * If the port is in the middle of closing, bail out now.
- */
- if (tty_hung_up_p(filp)) {
- retval = -EAGAIN;
- goto err_dec_count;
- }
-
- /*
* Start up the serial port.
*/
retval = uart_startup(tty, state, 0);
diff --git a/drivers/tty/synclink.c b/drivers/tty/synclink.c
index d48e040..b799170 100644
--- a/drivers/tty/synclink.c
+++ b/drivers/tty/synclink.c
@@ -3267,7 +3267,6 @@ static int block_til_ready(struct tty_struct *tty, struct file * filp,
DECLARE_WAITQUEUE(wait, current);
int retval;
bool do_clocal = false;
- bool extra_count = false;
unsigned long flags;
int dcd;
struct tty_port *port = &info->port;
@@ -3300,10 +3299,7 @@ static int block_til_ready(struct tty_struct *tty, struct file * filp,
__FILE__,__LINE__, tty->driver->name, port->count );
spin_lock_irqsave(&info->irq_spinlock, flags);
- if (!tty_hung_up_p(filp)) {
- extra_count = true;
- port->count--;
- }
+ port->count--;
spin_unlock_irqrestore(&info->irq_spinlock, flags);
port->blocked_open++;
@@ -3342,7 +3338,7 @@ static int block_til_ready(struct tty_struct *tty, struct file * filp,
remove_wait_queue(&port->open_wait, &wait);
/* FIXME: Racy on hangup during close wait */
- if (extra_count)
+ if (!tty_hung_up_p(filp))
port->count++;
port->blocked_open--;
@@ -3403,7 +3399,7 @@ static int mgsl_open(struct tty_struct *tty, struct file * filp)
__FILE__,__LINE__,tty->driver->name, info->port.count);
/* If port is closing, signal caller to try again */
- if (tty_hung_up_p(filp) || info->port.flags & ASYNC_CLOSING){
+ if (info->port.flags & ASYNC_CLOSING){
wait_event_interruptible_tty(tty, info->port.close_wait,
!(info->port.flags & ASYNC_CLOSING));
retval = ((info->port.flags & ASYNC_HUP_NOTIFY) ?
diff --git a/drivers/tty/synclink_gt.c b/drivers/tty/synclink_gt.c
index c359a91..ba1dbcd 100644
--- a/drivers/tty/synclink_gt.c
+++ b/drivers/tty/synclink_gt.c
@@ -673,7 +673,7 @@ static int open(struct tty_struct *tty, struct file *filp)
DBGINFO(("%s open, old ref count = %d\n", info->device_name, info->port.count));
/* If port is closing, signal caller to try again */
- if (tty_hung_up_p(filp) || info->port.flags & ASYNC_CLOSING){
+ if (info->port.flags & ASYNC_CLOSING){
wait_event_interruptible_tty(tty, info->port.close_wait,
!(info->port.flags & ASYNC_CLOSING));
retval = ((info->port.flags & ASYNC_HUP_NOTIFY) ?
@@ -3273,7 +3273,6 @@ static int block_til_ready(struct tty_struct *tty, struct file *filp,
DECLARE_WAITQUEUE(wait, current);
int retval;
bool do_clocal = false;
- bool extra_count = false;
unsigned long flags;
int cd;
struct tty_port *port = &info->port;
@@ -3300,10 +3299,7 @@ static int block_til_ready(struct tty_struct *tty, struct file *filp,
add_wait_queue(&port->open_wait, &wait);
spin_lock_irqsave(&info->lock, flags);
- if (!tty_hung_up_p(filp)) {
- extra_count = true;
- port->count--;
- }
+ port->count--;
spin_unlock_irqrestore(&info->lock, flags);
port->blocked_open++;
@@ -3338,7 +3334,7 @@ static int block_til_ready(struct tty_struct *tty, struct file *filp,
set_current_state(TASK_RUNNING);
remove_wait_queue(&port->open_wait, &wait);
- if (extra_count)
+ if (!tty_hung_up_p(filp))
port->count++;
port->blocked_open--;
diff --git a/drivers/tty/synclinkmp.c b/drivers/tty/synclinkmp.c
index 53ba853..c3f9091 100644
--- a/drivers/tty/synclinkmp.c
+++ b/drivers/tty/synclinkmp.c
@@ -753,7 +753,7 @@ static int open(struct tty_struct *tty, struct file *filp)
__FILE__,__LINE__,tty->driver->name, info->port.count);
/* If port is closing, signal caller to try again */
- if (tty_hung_up_p(filp) || info->port.flags & ASYNC_CLOSING){
+ if (info->port.flags & ASYNC_CLOSING){
wait_event_interruptible_tty(tty, info->port.close_wait,
!(info->port.flags & ASYNC_CLOSING));
retval = ((info->port.flags & ASYNC_HUP_NOTIFY) ?
@@ -3288,7 +3288,6 @@ static int block_til_ready(struct tty_struct *tty, struct file *filp,
DECLARE_WAITQUEUE(wait, current);
int retval;
bool do_clocal = false;
- bool extra_count = false;
unsigned long flags;
int cd;
struct tty_port *port = &info->port;
@@ -3322,10 +3321,7 @@ static int block_til_ready(struct tty_struct *tty, struct file *filp,
__FILE__,__LINE__, tty->driver->name, port->count );
spin_lock_irqsave(&info->lock, flags);
- if (!tty_hung_up_p(filp)) {
- extra_count = true;
- port->count--;
- }
+ port->count--;
spin_unlock_irqrestore(&info->lock, flags);
port->blocked_open++;
@@ -3362,8 +3358,7 @@ static int block_til_ready(struct tty_struct *tty, struct file *filp,
set_current_state(TASK_RUNNING);
remove_wait_queue(&port->open_wait, &wait);
-
- if (extra_count)
+ if (!tty_hung_up_p(filp))
port->count++;
port->blocked_open--;
diff --git a/drivers/tty/tty_port.c b/drivers/tty/tty_port.c
index 9209d63..1b93357 100644
--- a/drivers/tty/tty_port.c
+++ b/drivers/tty/tty_port.c
@@ -365,7 +365,7 @@ int tty_port_block_til_ready(struct tty_port *port,
DEFINE_WAIT(wait);
/* block if port is in the process of being closed */
- if (tty_hung_up_p(filp) || port->flags & ASYNC_CLOSING) {
+ if (port->flags & ASYNC_CLOSING) {
wait_event_interruptible_tty(tty, port->close_wait,
!(port->flags & ASYNC_CLOSING));
if (port->flags & ASYNC_HUP_NOTIFY)
@@ -399,8 +399,7 @@ int tty_port_block_til_ready(struct tty_port *port,
/* The port lock protects the port counts */
spin_lock_irqsave(&port->lock, flags);
- if (!tty_hung_up_p(filp))
- port->count--;
+ port->count--;
port->blocked_open++;
spin_unlock_irqrestore(&port->lock, flags);
@@ -593,8 +592,7 @@ int tty_port_open(struct tty_port *port, struct tty_struct *tty,
struct file *filp)
{
spin_lock_irq(&port->lock);
- if (!tty_hung_up_p(filp))
- ++port->count;
+ ++port->count;
spin_unlock_irq(&port->lock);
tty_port_tty_set(port, tty);
diff --git a/net/irda/ircomm/ircomm_tty.c b/net/irda/ircomm/ircomm_tty.c
index 2ba8b97..61ceb4c 100644
--- a/net/irda/ircomm/ircomm_tty.c
+++ b/net/irda/ircomm/ircomm_tty.c
@@ -320,8 +320,7 @@ static int ircomm_tty_block_til_ready(struct ircomm_tty_cb *self,
__FILE__, __LINE__, tty->driver->name, port->count);
spin_lock_irqsave(&port->lock, flags);
- if (!tty_hung_up_p(filp))
- port->count--;
+ port->count--;
port->blocked_open++;
spin_unlock_irqrestore(&port->lock, flags);
@@ -458,8 +457,7 @@ static int ircomm_tty_open(struct tty_struct *tty, struct file *filp)
/*
* If the port is the middle of closing, bail out now
*/
- if (tty_hung_up_p(filp) ||
- test_bit(ASYNCB_CLOSING, &self->port.flags)) {
+ if (test_bit(ASYNCB_CLOSING, &self->port.flags)) {
/* Hm, why are we blocking on ASYNC_CLOSING if we
* do return -EAGAIN/-ERESTARTSYS below anyway?
--
2.0.0
--
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