[PATCH 2/4] tty: Simplify calling of put_pid.

From: Eric W. Biederman
Date: Sun Mar 18 2007 - 15:04:27 EST



This patch should contain no functional changes.

At somepoint I got confused and thought put_pid could not
be called while a spin lock was held. While it may be nice
to avoid that to reduce lock hold times put_pid can be safely
called while we hold a spin lock.

This patch removes all of the complications from the code
introduced by my misunderstanding, making the code a little
more readable.

Signed-off-by: Eric W. Biederman <ebiederm@xxxxxxxxxxxx>
---
drivers/char/tty_io.c | 23 ++++++-----------------
1 files changed, 6 insertions(+), 17 deletions(-)

diff --git a/drivers/char/tty_io.c b/drivers/char/tty_io.c
index 583730f..01fcfaf 100644
--- a/drivers/char/tty_io.c
+++ b/drivers/char/tty_io.c
@@ -155,8 +155,7 @@ int tty_ioctl(struct inode * inode, struct file * file,
unsigned int cmd, unsigned long arg);
static int tty_fasync(int fd, struct file * filp, int on);
static void release_tty(struct tty_struct *tty, int idx);
-static struct pid *__proc_set_tty(struct task_struct *tsk,
- struct tty_struct *tty);
+static void __proc_set_tty(struct task_struct *tsk, struct tty_struct *tty);

/**
* alloc_tty_struct - allocate a tty object
@@ -1534,10 +1533,9 @@ void disassociate_ctty(int on_exit)
}

spin_lock_irq(&current->sighand->siglock);
- tty_pgrp = current->signal->tty_old_pgrp;
+ put_pid(current->signal->tty_old_pgrp);
current->signal->tty_old_pgrp = NULL;
spin_unlock_irq(&current->sighand->siglock);
- put_pid(tty_pgrp);

mutex_lock(&tty_mutex);
/* It is possible that do_tty_hangup has free'd this tty */
@@ -2508,7 +2506,6 @@ static int tty_open(struct inode * inode, struct file * filp)
int index;
dev_t device = inode->i_rdev;
unsigned short saved_flags = filp->f_flags;
- struct pid *old_pgrp;

nonseekable_open(inode, filp);

@@ -2602,17 +2599,15 @@ got_driver:
goto retry_open;
}

- old_pgrp = NULL;
mutex_lock(&tty_mutex);
spin_lock_irq(&current->sighand->siglock);
if (!noctty &&
current->signal->leader &&
!current->signal->tty &&
tty->session == NULL)
- old_pgrp = __proc_set_tty(current, tty);
+ __proc_set_tty(current, tty);
spin_unlock_irq(&current->sighand->siglock);
mutex_unlock(&tty_mutex);
- put_pid(old_pgrp);
return 0;
}

@@ -3838,9 +3833,8 @@ void proc_clear_tty(struct task_struct *p)
spin_unlock_irq(&p->sighand->siglock);
}

-static struct pid *__proc_set_tty(struct task_struct *tsk, struct tty_struct *tty)
+static void __proc_set_tty(struct task_struct *tsk, struct tty_struct *tty)
{
- struct pid *old_pgrp;
if (tty) {
/* We should not have a session or pgrp to here but.... */
put_pid(tty->session);
@@ -3848,21 +3842,16 @@ static struct pid *__proc_set_tty(struct task_struct *tsk, struct tty_struct *tt
tty->session = get_pid(task_session(tsk));
tty->pgrp = get_pid(task_pgrp(tsk));
}
- old_pgrp = tsk->signal->tty_old_pgrp;
+ put_pid(tsk->signal->tty_old_pgrp);
tsk->signal->tty = tty;
tsk->signal->tty_old_pgrp = NULL;
- return old_pgrp;
}

void proc_set_tty(struct task_struct *tsk, struct tty_struct *tty)
{
- struct pid *old_pgrp;
-
spin_lock_irq(&tsk->sighand->siglock);
- old_pgrp = __proc_set_tty(tsk, tty);
+ __proc_set_tty(tsk, tty);
spin_unlock_irq(&tsk->sighand->siglock);
-
- put_pid(old_pgrp);
}

struct tty_struct *get_current_tty(void)
--
1.5.0.g53756

-
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