[PATCH 9/12] tty: Update the tty layer to work with struct pid.

From: Eric W. Biederman
Date: Wed Dec 13 2006 - 06:21:30 EST

Of kernel subsystems that work with pids the tty layer
is probably the largest consumer. But it has the nice
virtue that the assiation with a session only lasts until
the session leader exits. Which means that no reference
counting is required. So using struct pid winds up
being a simple optimization to avoid hash table lookups.

In the long term the use of pid_nr also ensures that
when we have multiple pid spaces mixed everything will
work correctly.

Signed-off-by: Eric W. Biederman <eric@xxxxxxxxxxxxxxxx>
---
arch/um/drivers/line.c | 2 +-
drivers/char/ip2/ip2main.c | 4 +-
drivers/char/n_tty.c | 12 ++--
drivers/char/tty_io.c | 129 ++++++++++++++++++++++++++-----------------
drivers/char/vt.c | 4 +-
fs/proc/array.c | 2 +-
include/linux/init_task.h | 2 +-
include/linux/sched.h | 2 +-
include/linux/tty.h | 4 +-
kernel/fork.c | 2 +-
kernel/sys.c | 1 -
11 files changed, 95 insertions(+), 69 deletions(-)

diff --git a/arch/um/drivers/line.c b/arch/um/drivers/line.c
index 83301e1..3c1a1d4 100644
--- a/arch/um/drivers/line.c
+++ b/arch/um/drivers/line.c
@@ -737,7 +737,7 @@ static irqreturn_t winch_interrupt(int irq, void *data)
line = tty->driver_data;
chan_window_size(&line->chan_list, &tty->winsize.ws_row,
&tty->winsize.ws_col);
- kill_pg(tty->pgrp, SIGWINCH, 1);
+ kill_pgrp(tty->pgrp, SIGWINCH, 1);
}
out:
if(winch->fd != -1)
diff --git a/drivers/char/ip2/ip2main.c b/drivers/char/ip2/ip2main.c
index 7c70310..83c7258 100644
--- a/drivers/char/ip2/ip2main.c
+++ b/drivers/char/ip2/ip2main.c
@@ -1271,8 +1271,8 @@ static void do_input(struct work_struct *work)
// code duplicated from n_tty (ldisc)
static inline void isig(int sig, struct tty_struct *tty, int flush)
{
- if (tty->pgrp > 0)
- kill_pg(tty->pgrp, sig, 1);
+ if (tty->pgrp)
+ kill_pgrp(tty->pgrp, sig, 1);
if (flush || !L_NOFLSH(tty)) {
if ( tty->ldisc.flush_buffer )
tty->ldisc.flush_buffer(tty);
diff --git a/drivers/char/n_tty.c b/drivers/char/n_tty.c
index 7f1ded8..2b50a50 100644
--- a/drivers/char/n_tty.c
+++ b/drivers/char/n_tty.c
@@ -579,8 +579,8 @@ static void eraser(unsigned char c, struct tty_struct *tty)

static inline void isig(int sig, struct tty_struct *tty, int flush)
{
- if (tty->pgrp > 0)
- kill_pg(tty->pgrp, sig, 1);
+ if (tty->pgrp)
+ kill_pgrp(tty->pgrp, sig, 1);
if (flush || !L_NOFLSH(tty)) {
n_tty_flush_buffer(tty);
if (tty->driver->flush_buffer)
@@ -1185,13 +1185,13 @@ static int job_control(struct tty_struct *tty, struct file *file)
/* don't stop on /dev/console */
if (file->f_op->write != redirected_tty_write &&
current->signal->tty == tty) {
- if (tty->pgrp <= 0)
- printk("read_chan: tty->pgrp <= 0!\n");
- else if (process_group(current) != tty->pgrp) {
+ if (!tty->pgrp)
+ printk("read_chan: no tty->pgrp!\n");
+ else if (task_pgrp(current) != tty->pgrp) {
if (is_ignored(SIGTTIN) ||
is_current_pgrp_orphaned())
return -EIO;
- kill_pg(process_group(current), SIGTTIN, 1);
+ kill_pgrp(task_pgrp(current), SIGTTIN, 1);
return -ERESTARTSYS;
}
}
diff --git a/drivers/char/tty_io.c b/drivers/char/tty_io.c
index d8fdf45..fe98f8c 100644
--- a/drivers/char/tty_io.c
+++ b/drivers/char/tty_io.c
@@ -155,7 +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_mem(struct tty_struct *tty, int idx);
-static void __proc_set_tty(struct task_struct *tsk, struct tty_struct *tty);
+static struct pid *__proc_set_tty(struct task_struct *tsk, struct tty_struct *tty);

/**
* alloc_tty_struct - allocate a tty object
@@ -1110,17 +1110,17 @@ int tty_check_change(struct tty_struct * tty)
{
if (current->signal->tty != tty)
return 0;
- if (tty->pgrp <= 0) {
- printk(KERN_WARNING "tty_check_change: tty->pgrp <= 0!\n");
+ if (!tty->pgrp) {
+ printk(KERN_WARNING "tty_check_change: tty->pgrp == NULL!\n");
return 0;
}
- if (process_group(current) == tty->pgrp)
+ if (task_pgrp(current) == tty->pgrp)
return 0;
if (is_ignored(SIGTTOU))
return 0;
if (is_current_pgrp_orphaned())
return -EIO;
- (void) kill_pg(process_group(current), SIGTTOU, 1);
+ (void) kill_pgrp(task_pgrp(current), SIGTTOU, 1);
return -ERESTARTSYS;
}

@@ -1355,8 +1355,8 @@ static void do_tty_hangup(struct work_struct *work)
tty_release is called */

read_lock(&tasklist_lock);
- if (tty->session > 0) {
- do_each_task_pid(tty->session, PIDTYPE_SID, p) {
+ if (tty->session) {
+ do_each_pid_task(tty->session, PIDTYPE_SID, p) {
spin_lock_irq(&p->sighand->siglock);
if (p->signal->tty == tty)
p->signal->tty = NULL;
@@ -1366,16 +1366,17 @@ static void do_tty_hangup(struct work_struct *work)
}
__group_send_sig_info(SIGHUP, SEND_SIG_PRIV, p);
__group_send_sig_info(SIGCONT, SEND_SIG_PRIV, p);
- if (tty->pgrp > 0)
- p->signal->tty_old_pgrp = tty->pgrp;
+ put_pid(p->signal->tty_old_pgrp); /* A noop */
+ if (tty->pgrp)
+ p->signal->tty_old_pgrp = get_pid(tty->pgrp);
spin_unlock_irq(&p->sighand->siglock);
- } while_each_task_pid(tty->session, PIDTYPE_SID, p);
+ } while_each_pid_task(tty->session, PIDTYPE_SID, p);
}
read_unlock(&tasklist_lock);

tty->flags = 0;
- tty->session = 0;
- tty->pgrp = -1;
+ tty->session = NULL;
+ tty->pgrp = NULL;
tty->ctrl_status = 0;
/*
* If one of the devices matches a console pointer, we
@@ -1460,12 +1461,12 @@ int tty_hung_up_p(struct file * filp)

EXPORT_SYMBOL(tty_hung_up_p);

-static void session_clear_tty(pid_t session)
+static void session_clear_tty(struct pid *session)
{
struct task_struct *p;
- do_each_task_pid(session, PIDTYPE_SID, p) {
+ do_each_pid_task(session, PIDTYPE_SID, p) {
proc_clear_tty(p);
- } while_each_task_pid(session, PIDTYPE_SID, p);
+ } while_each_pid_task(session, PIDTYPE_SID, p);
}

/**
@@ -1495,48 +1496,54 @@ static void session_clear_tty(pid_t session)
void disassociate_ctty(int on_exit)
{
struct tty_struct *tty;
- int tty_pgrp = -1;
+ struct pid *tty_pgrp = NULL;

lock_kernel();

mutex_lock(&tty_mutex);
tty = get_current_tty();
if (tty) {
- tty_pgrp = tty->pgrp;
+ tty_pgrp = get_pid(tty->pgrp);
mutex_unlock(&tty_mutex);
/* XXX: here we race, there is nothing protecting tty */
if (on_exit && tty->driver->type != TTY_DRIVER_TYPE_PTY)
tty_vhangup(tty);
} else if (on_exit) {
- pid_t old_pgrp;
+ struct pid *old_pgrp;
spin_lock_irq(&current->sighand->siglock);
old_pgrp = current->signal->tty_old_pgrp;
- current->signal->tty_old_pgrp = 0;
+ current->signal->tty_old_pgrp = NULL;
spin_unlock_irq(&current->sighand->siglock);
if (old_pgrp) {
- kill_pg(old_pgrp, SIGHUP, on_exit);
- kill_pg(old_pgrp, SIGCONT, on_exit);
+ kill_pgrp(old_pgrp, SIGHUP, on_exit);
+ kill_pgrp(old_pgrp, SIGCONT, on_exit);
+ put_pid(old_pgrp);
}
mutex_unlock(&tty_mutex);
unlock_kernel();
return;
}
- if (tty_pgrp > 0) {
- kill_pg(tty_pgrp, SIGHUP, on_exit);
+ if (tty_pgrp) {
+ kill_pgrp(tty_pgrp, SIGHUP, on_exit);
if (!on_exit)
- kill_pg(tty_pgrp, SIGCONT, on_exit);
+ kill_pgrp(tty_pgrp, SIGCONT, on_exit);
+ put_pid(tty_pgrp);
}

spin_lock_irq(&current->sighand->siglock);
+ tty_pgrp = current->signal->tty_old_pgrp;
current->signal->tty_old_pgrp = 0;
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 */
tty = get_current_tty();
if (tty) {
- tty->session = 0;
- tty->pgrp = 0;
+ put_pid(tty->session);
+ put_pid(tty->pgrp);
+ tty->session = NULL;
+ tty->pgrp = NULL;
} else {
#ifdef TTY_DEBUG_HANGUP
printk(KERN_DEBUG "error attempted to write to tty [0x%p]"
@@ -1547,7 +1554,7 @@ void disassociate_ctty(int on_exit)

/* Now clear signal->tty under the lock */
read_lock(&tasklist_lock);
- session_clear_tty(process_session(current));
+ session_clear_tty(task_session(current));
read_unlock(&tasklist_lock);
unlock_kernel();
}
@@ -2484,6 +2491,7 @@ 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);

@@ -2577,15 +2585,17 @@ 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 == 0)
- __proc_set_tty(current, tty);
+ tty->session == NULL)
+ old_pgrp = __proc_set_tty(current, tty);
spin_unlock_irq(&current->sighand->siglock);
mutex_unlock(&tty_mutex);
+ put_pid(old_pgrp);
return 0;
}

@@ -2724,9 +2734,18 @@ static int tty_fasync(int fd, struct file * filp, int on)
return retval;

if (on) {
+ enum pid_type type;
+ struct pid *pid;
if (!waitqueue_active(&tty->read_wait))
tty->minimum_to_wake = 1;
- retval = f_setown(filp, (-tty->pgrp) ? : current->pid, 0);
+ if (tty->pgrp) {
+ pid = tty->pgrp;
+ type = PIDTYPE_PGID;
+ } else {
+ pid = task_pid(current);
+ type = PIDTYPE_PID;
+ }
+ retval = __f_setown(filp, pid, type, 0);
if (retval)
return retval;
} else {
@@ -2828,10 +2847,10 @@ static int tiocswinsz(struct tty_struct *tty, struct tty_struct *real_tty,
}
}
#endif
- if (tty->pgrp > 0)
- kill_pg(tty->pgrp, SIGWINCH, 1);
- if ((real_tty->pgrp != tty->pgrp) && (real_tty->pgrp > 0))
- kill_pg(real_tty->pgrp, SIGWINCH, 1);
+ if (tty->pgrp)
+ kill_pgrp(tty->pgrp, SIGWINCH, 1);
+ if ((real_tty->pgrp != tty->pgrp) && real_tty->pgrp)
+ kill_pgrp(real_tty->pgrp, SIGWINCH, 1);
tty->winsize = tmp_ws;
real_tty->winsize = tmp_ws;
done:
@@ -2916,8 +2935,7 @@ static int fionbio(struct file *file, int __user *p)
static int tiocsctty(struct tty_struct *tty, int arg)
{
int ret = 0;
- if (current->signal->leader &&
- (process_session(current) == tty->session))
+ if (current->signal->leader && (task_session(current) == tty->session))
return ret;

mutex_lock(&tty_mutex);
@@ -2930,7 +2948,7 @@ static int tiocsctty(struct tty_struct *tty, int arg)
goto unlock;
}

- if (tty->session > 0) {
+ if (tty->session) {
/*
* This tty is already the controlling
* tty for another session group!
@@ -2973,7 +2991,7 @@ static int tiocgpgrp(struct tty_struct *tty, struct tty_struct *real_tty, pid_t
*/
if (tty == real_tty && current->signal->tty != real_tty)
return -ENOTTY;
- return put_user(real_tty->pgrp, p);
+ return put_user(pid_nr(real_tty->pgrp), p);
}

/**
@@ -3000,7 +3018,7 @@ static int tiocspgrp(struct tty_struct *tty, struct tty_struct *real_tty, pid_t
return retval;
if (!current->signal->tty ||
(current->signal->tty != real_tty) ||
- (real_tty->session != process_session(current)))
+ (real_tty->session != task_session(current)))
return -ENOTTY;
if (get_user(pgrp_nr, p))
return -EFAULT;
@@ -3015,7 +3033,8 @@ static int tiocspgrp(struct tty_struct *tty, struct tty_struct *real_tty, pid_t
if (session_of_pgrp(pgrp) != task_session(current))
goto out_unlock;
retval = 0;
- real_tty->pgrp = pgrp_nr;
+ put_pid(real_tty->pgrp);
+ real_tty->pgrp = get_pid(pgrp);
out_unlock:
rcu_read_unlock();
return retval;
@@ -3041,9 +3060,9 @@ static int tiocgsid(struct tty_struct *tty, struct tty_struct *real_tty, pid_t _
*/
if (tty == real_tty && current->signal->tty != real_tty)
return -ENOTTY;
- if (real_tty->session <= 0)
+ if (!real_tty->session)
return -ENOTTY;
- return put_user(real_tty->session, p);
+ return put_user(pid_nr(real_tty->session), p);
}

/**
@@ -3343,7 +3362,7 @@ void __do_SAK(struct tty_struct *tty)
tty_hangup(tty);
#else
struct task_struct *g, *p;
- int session;
+ struct pid *session;
int i;
struct file *filp;
struct tty_ldisc *disc;
@@ -3364,12 +3383,12 @@ void __do_SAK(struct tty_struct *tty)

read_lock(&tasklist_lock);
/* Kill the entire session */
- do_each_task_pid(session, PIDTYPE_SID, p) {
+ do_each_pid_task(session, PIDTYPE_SID, p) {
printk(KERN_NOTICE "SAK: killed process %d"
" (%s): process_session(p)==tty->session\n",
p->pid, p->comm);
send_sig(SIGKILL, p, 1);
- } while_each_task_pid(session, PIDTYPE_SID, p);
+ } while_each_pid_task(session, PIDTYPE_SID, p);
/* Now kill any processes that happen to have the
* tty open.
*/
@@ -3538,7 +3557,8 @@ static void initialize_tty_struct(struct tty_struct *tty)
memset(tty, 0, sizeof(struct tty_struct));
tty->magic = TTY_MAGIC;
tty_ldisc_assign(tty, tty_ldisc_get(N_TTY));
- tty->pgrp = -1;
+ tty->session = NULL;
+ tty->pgrp = NULL;
tty->overrun_time = jiffies;
tty->buf.head = tty->buf.tail = NULL;
tty_buffer_init(tty);
@@ -3809,21 +3829,28 @@ void proc_clear_tty(struct task_struct *p)
}
EXPORT_SYMBOL(proc_clear_tty);

-static void __proc_set_tty(struct task_struct *tsk, struct tty_struct *tty)
+static struct pid *__proc_set_tty(struct task_struct *tsk, struct tty_struct *tty)
{
+ struct pid *old_pgrp;
if (tty) {
- tty->session = process_session(tsk);
- tty->pgrp = process_group(tsk);
+ tty->session = get_pid(task_session(tsk));
+ tty->pgrp = get_pid(task_pgrp(tsk));
}
+ old_pgrp = tsk->signal->tty_old_pgrp;
tsk->signal->tty = tty;
- tsk->signal->tty_old_pgrp = 0;
+ 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);
- __proc_set_tty(tsk, tty);
+ old_pgrp = __proc_set_tty(tsk, tty);
spin_unlock_irq(&tsk->sighand->siglock);
+
+ put_pid(old_pgrp);
}

struct tty_struct *get_current_tty(void)
diff --git a/drivers/char/vt.c b/drivers/char/vt.c
index a8239da..4d52cab 100644
--- a/drivers/char/vt.c
+++ b/drivers/char/vt.c
@@ -869,8 +869,8 @@ int vc_resize(struct vc_data *vc, unsigned int cols, unsigned int lines)
ws.ws_col = vc->vc_cols;
ws.ws_ypixel = vc->vc_scan_lines;
if ((ws.ws_row != cws->ws_row || ws.ws_col != cws->ws_col) &&
- vc->vc_tty->pgrp > 0)
- kill_pg(vc->vc_tty->pgrp, SIGWINCH, 1);
+ vc->vc_tty->pgrp)
+ kill_pgrp(vc->vc_tty->pgrp, SIGWINCH, 1);
*cws = ws;
}

diff --git a/fs/proc/array.c b/fs/proc/array.c
index 70e4fab..07c9cdb 100644
--- a/fs/proc/array.c
+++ b/fs/proc/array.c
@@ -351,7 +351,7 @@ static int do_task_stat(struct task_struct *task, char * buffer, int whole)
struct signal_struct *sig = task->signal;

if (sig->tty) {
- tty_pgrp = sig->tty->pgrp;
+ tty_pgrp = pid_nr(sig->tty->pgrp);
tty_nr = new_encode_dev(tty_devnum(sig->tty));
}

diff --git a/include/linux/init_task.h b/include/linux/init_task.h
index b531515..9991297 100644
--- a/include/linux/init_task.h
+++ b/include/linux/init_task.h
@@ -66,7 +66,7 @@
.cpu_timers = INIT_CPU_TIMERS(sig.cpu_timers), \
.rlim = INIT_RLIMITS, \
.pgrp = 1, \
- .tty_old_pgrp = 0, \
+ .tty_old_pgrp = NULL, \
{ .__session = 1}, \
}

diff --git a/include/linux/sched.h b/include/linux/sched.h
index ea92e5c..ef0d6fe 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -436,7 +436,7 @@ struct signal_struct {

/* job control IDs */
pid_t pgrp;
- pid_t tty_old_pgrp;
+ struct pid *tty_old_pgrp;

union {
pid_t session __deprecated;
diff --git a/include/linux/tty.h b/include/linux/tty.h
index 13a4918..f07e390 100644
--- a/include/linux/tty.h
+++ b/include/linux/tty.h
@@ -177,8 +177,8 @@ struct tty_struct {
struct mutex termios_mutex;
struct ktermios *termios, *termios_locked;
char name[64];
- int pgrp;
- int session;
+ struct pid *pgrp;
+ struct pid *session;
unsigned long flags;
int count;
struct winsize winsize;
diff --git a/kernel/fork.c b/kernel/fork.c
index d16c566..24b4af0 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -869,7 +869,7 @@ static inline int copy_signal(unsigned long clone_flags, struct task_struct * ts
sig->it_prof_incr = cputime_zero;

sig->leader = 0; /* session leadership doesn't inherit */
- sig->tty_old_pgrp = 0;
+ sig->tty_old_pgrp = NULL;

sig->utime = sig->stime = sig->cutime = sig->cstime = cputime_zero;
sig->nvcsw = sig->nivcsw = sig->cnvcsw = sig->cnivcsw = 0;
diff --git a/kernel/sys.c b/kernel/sys.c
index c7675c1..a8f2ebe 100644
--- a/kernel/sys.c
+++ b/kernel/sys.c
@@ -1503,7 +1503,6 @@ asmlinkage long sys_setsid(void)

spin_lock(&group_leader->sighand->siglock);
group_leader->signal->tty = NULL;
- group_leader->signal->tty_old_pgrp = 0;
spin_unlock(&group_leader->sighand->siglock);

err = process_group(group_leader);
--
1.4.4.1.g278f

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