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Commit 2a65f1d9 authored by Eric W. Biederman's avatar Eric W. Biederman Committed by Linus Torvalds
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tty: simplify calling of put_pid. 



This patch should contain no functional changes.

At some point 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: default avatarEric W. Biederman <ebiederm@xmission.com>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent f67c3627

drivers/char/tty_io.c

+6 −17
Original line number Diff line number Diff line
@@ -153,8 +153,7 @@ 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
@@ -1532,10 +1531,9 @@ 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 */
@@ -2506,7 +2504,6 @@ 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);
@@ -2600,17 +2597,15 @@ 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;

}
@@ -3835,9 +3830,8 @@ 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);
@@ -3845,21 +3839,16 @@ 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)