From e359a4e38d229d53e28905863a1fabf41debd591 Mon Sep 17 00:00:00 2001 From: Peter Hurley Date: Mon, 16 Jun 2014 09:17:06 -0400 Subject: [PATCH] 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 CC: Samuel Ortiz CC: "David S. Miller" Signed-off-by: Peter Hurley Acked-by: Jesper Nilsson Signed-off-by: Greg Kroah-Hartman --- 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 8320abd1ef14..a63970f76967 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 30d26029b21e..cdd1a69261dd 100644 --- a/drivers/staging/dgrp/dgrp_tty.c +++ b/drivers/staging/dgrp/dgrp_tty.c @@ -631,16 +631,6 @@ static int dgrp_tty_open(struct tty_struct *tty, struct file *file) un->un_tty = tty; 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 a57bb5ab761c..fd66f57390d0 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 d567ac5d3af4..58e6f61a87e4 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 3e08df52d68d..1a5fbf7ab347 100644 --- a/drivers/tty/serial/serial_core.c +++ b/drivers/tty/serial/serial_core.c @@ -1583,14 +1583,6 @@ static int uart_open(struct tty_struct *tty, struct file *filp) (state->uart_port->flags & UPF_LOW_LATENCY) ? 1 : 0; 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. */ diff --git a/drivers/tty/synclink.c b/drivers/tty/synclink.c index d48e040cd8c5..b7991707ffc0 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 c359a91f7346..ba1dbcdf4609 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 53ba8537de8d..c3f90910fed9 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 9209d6331b8e..1b9335796da4 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 2ba8b9705bb7..61ceb4cdb4a2 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? -- 2.20.1