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linux-next/include/linux/tty.h
Alan Cox c65c9bc3ef tty: rewrite the ldisc locking 
There are several pretty much unfixable races in the old ldisc code, especially
with respect to pty behaviour and also to hangup. It's easier to rewrite the
code than simply try and patch it up.

This patch
- splits the ldisc from the tty (so we will be able to refcount it more cleanly
  later)
- introduces a mutex lock for ldisc changing on an active device
- fixes the complete mess that hangup caused
- implements hopefully correct setldisc/close/hangup locking

There are still some problems around pty pairs that have always been there but
at least it is now possible to understand the code and fix further problems.

This fixes the following known bugs
- hang up can leak ldisc references
- hang up may not call open/close on ldisc in a matched way
- pty/tty pairs can deadlock during an ldisc change
- reading the ldisc proc files can cause every ldisc to be loaded

and probably a few other of the mysterious ldisc race reports.

I'm sure it also adds the odd new one.

Signed-off-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2009-06-11 08:51:01 -07:00

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#ifndef _LINUX_TTY_H
#define _LINUX_TTY_H
/*
* 'tty.h' defines some structures used by tty_io.c and some defines.
*/
#ifdef __KERNEL__
#include <linux/fs.h>
#include <linux/major.h>
#include <linux/termios.h>
#include <linux/workqueue.h>
#include <linux/tty_driver.h>
#include <linux/tty_ldisc.h>
#include <linux/mutex.h>
#include <asm/system.h>
/*
* (Note: the *_driver.minor_start values 1, 64, 128, 192 are
* hardcoded at present.)
*/
#define NR_UNIX98_PTY_DEFAULT 4096 /* Default maximum for Unix98 ptys */
#define NR_UNIX98_PTY_MAX (1 << MINORBITS) /* Absolute limit */
#define NR_LDISCS 19
/* line disciplines */
#define N_TTY 0
#define N_SLIP 1
#define N_MOUSE 2
#define N_PPP 3
#define N_STRIP 4
#define N_AX25 5
#define N_X25 6 /* X.25 async */
#define N_6PACK 7
#define N_MASC 8 /* Reserved for Mobitex module <kaz@cafe.net> */
#define N_R3964 9 /* Reserved for Simatic R3964 module */
#define N_PROFIBUS_FDL 10 /* Reserved for Profibus */
#define N_IRDA 11 /* Linux IrDa - http://irda.sourceforge.net/ */
#define N_SMSBLOCK 12 /* SMS block mode - for talking to GSM data */
/* cards about SMS messages */
#define N_HDLC 13 /* synchronous HDLC */
#define N_SYNC_PPP 14 /* synchronous PPP */
#define N_HCI 15 /* Bluetooth HCI UART */
#define N_GIGASET_M101 16 /* Siemens Gigaset M101 serial DECT adapter */
#define N_SLCAN 17 /* Serial / USB serial CAN Adaptors */
#define N_PPS 18 /* Pulse per Second */
/*
* This character is the same as _POSIX_VDISABLE: it cannot be used as
* a c_cc[] character, but indicates that a particular special character
* isn't in use (eg VINTR has no character etc)
*/
#define __DISABLED_CHAR '\0'
struct tty_buffer {
struct tty_buffer *next;
char *char_buf_ptr;
unsigned char *flag_buf_ptr;
int used;
int size;
int commit;
int read;
/* Data points here */
unsigned long data[0];
};
struct tty_bufhead {
struct delayed_work work;
spinlock_t lock;
struct tty_buffer *head; /* Queue head */
struct tty_buffer *tail; /* Active buffer */
struct tty_buffer *free; /* Free queue head */
int memory_used; /* Buffer space used excluding
free queue */
};
/*
* When a break, frame error, or parity error happens, these codes are
* stuffed into the flags buffer.
*/
#define TTY_NORMAL 0
#define TTY_BREAK 1
#define TTY_FRAME 2
#define TTY_PARITY 3
#define TTY_OVERRUN 4
#define INTR_CHAR(tty) ((tty)->termios->c_cc[VINTR])
#define QUIT_CHAR(tty) ((tty)->termios->c_cc[VQUIT])
#define ERASE_CHAR(tty) ((tty)->termios->c_cc[VERASE])
#define KILL_CHAR(tty) ((tty)->termios->c_cc[VKILL])
#define EOF_CHAR(tty) ((tty)->termios->c_cc[VEOF])
#define TIME_CHAR(tty) ((tty)->termios->c_cc[VTIME])
#define MIN_CHAR(tty) ((tty)->termios->c_cc[VMIN])
#define SWTC_CHAR(tty) ((tty)->termios->c_cc[VSWTC])
#define START_CHAR(tty) ((tty)->termios->c_cc[VSTART])
#define STOP_CHAR(tty) ((tty)->termios->c_cc[VSTOP])
#define SUSP_CHAR(tty) ((tty)->termios->c_cc[VSUSP])
#define EOL_CHAR(tty) ((tty)->termios->c_cc[VEOL])
#define REPRINT_CHAR(tty) ((tty)->termios->c_cc[VREPRINT])
#define DISCARD_CHAR(tty) ((tty)->termios->c_cc[VDISCARD])
#define WERASE_CHAR(tty) ((tty)->termios->c_cc[VWERASE])
#define LNEXT_CHAR(tty) ((tty)->termios->c_cc[VLNEXT])
#define EOL2_CHAR(tty) ((tty)->termios->c_cc[VEOL2])
#define _I_FLAG(tty, f) ((tty)->termios->c_iflag & (f))
#define _O_FLAG(tty, f) ((tty)->termios->c_oflag & (f))
#define _C_FLAG(tty, f) ((tty)->termios->c_cflag & (f))
#define _L_FLAG(tty, f) ((tty)->termios->c_lflag & (f))
#define I_IGNBRK(tty) _I_FLAG((tty), IGNBRK)
#define I_BRKINT(tty) _I_FLAG((tty), BRKINT)
#define I_IGNPAR(tty) _I_FLAG((tty), IGNPAR)
#define I_PARMRK(tty) _I_FLAG((tty), PARMRK)
#define I_INPCK(tty) _I_FLAG((tty), INPCK)
#define I_ISTRIP(tty) _I_FLAG((tty), ISTRIP)
#define I_INLCR(tty) _I_FLAG((tty), INLCR)
#define I_IGNCR(tty) _I_FLAG((tty), IGNCR)
#define I_ICRNL(tty) _I_FLAG((tty), ICRNL)
#define I_IUCLC(tty) _I_FLAG((tty), IUCLC)
#define I_IXON(tty) _I_FLAG((tty), IXON)
#define I_IXANY(tty) _I_FLAG((tty), IXANY)
#define I_IXOFF(tty) _I_FLAG((tty), IXOFF)
#define I_IMAXBEL(tty) _I_FLAG((tty), IMAXBEL)
#define I_IUTF8(tty) _I_FLAG((tty), IUTF8)
#define O_OPOST(tty) _O_FLAG((tty), OPOST)
#define O_OLCUC(tty) _O_FLAG((tty), OLCUC)
#define O_ONLCR(tty) _O_FLAG((tty), ONLCR)
#define O_OCRNL(tty) _O_FLAG((tty), OCRNL)
#define O_ONOCR(tty) _O_FLAG((tty), ONOCR)
#define O_ONLRET(tty) _O_FLAG((tty), ONLRET)
#define O_OFILL(tty) _O_FLAG((tty), OFILL)
#define O_OFDEL(tty) _O_FLAG((tty), OFDEL)
#define O_NLDLY(tty) _O_FLAG((tty), NLDLY)
#define O_CRDLY(tty) _O_FLAG((tty), CRDLY)
#define O_TABDLY(tty) _O_FLAG((tty), TABDLY)
#define O_BSDLY(tty) _O_FLAG((tty), BSDLY)
#define O_VTDLY(tty) _O_FLAG((tty), VTDLY)
#define O_FFDLY(tty) _O_FLAG((tty), FFDLY)
#define C_BAUD(tty) _C_FLAG((tty), CBAUD)
#define C_CSIZE(tty) _C_FLAG((tty), CSIZE)
#define C_CSTOPB(tty) _C_FLAG((tty), CSTOPB)
#define C_CREAD(tty) _C_FLAG((tty), CREAD)
#define C_PARENB(tty) _C_FLAG((tty), PARENB)
#define C_PARODD(tty) _C_FLAG((tty), PARODD)
#define C_HUPCL(tty) _C_FLAG((tty), HUPCL)
#define C_CLOCAL(tty) _C_FLAG((tty), CLOCAL)
#define C_CIBAUD(tty) _C_FLAG((tty), CIBAUD)
#define C_CRTSCTS(tty) _C_FLAG((tty), CRTSCTS)
#define L_ISIG(tty) _L_FLAG((tty), ISIG)
#define L_ICANON(tty) _L_FLAG((tty), ICANON)
#define L_XCASE(tty) _L_FLAG((tty), XCASE)
#define L_ECHO(tty) _L_FLAG((tty), ECHO)
#define L_ECHOE(tty) _L_FLAG((tty), ECHOE)
#define L_ECHOK(tty) _L_FLAG((tty), ECHOK)
#define L_ECHONL(tty) _L_FLAG((tty), ECHONL)
#define L_NOFLSH(tty) _L_FLAG((tty), NOFLSH)
#define L_TOSTOP(tty) _L_FLAG((tty), TOSTOP)
#define L_ECHOCTL(tty) _L_FLAG((tty), ECHOCTL)
#define L_ECHOPRT(tty) _L_FLAG((tty), ECHOPRT)
#define L_ECHOKE(tty) _L_FLAG((tty), ECHOKE)
#define L_FLUSHO(tty) _L_FLAG((tty), FLUSHO)
#define L_PENDIN(tty) _L_FLAG((tty), PENDIN)
#define L_IEXTEN(tty) _L_FLAG((tty), IEXTEN)
struct device;
struct signal_struct;
/*
* Port level information. Each device keeps its own port level information
* so provide a common structure for those ports wanting to use common support
* routines.
*
* The tty port has a different lifetime to the tty so must be kept apart.
* In addition be careful as tty -> port mappings are valid for the life
* of the tty object but in many cases port -> tty mappings are valid only
* until a hangup so don't use the wrong path.
*/
struct tty_port;
struct tty_port_operations {
/* Return 1 if the carrier is raised */
int (*carrier_raised)(struct tty_port *port);
void (*dtr_rts)(struct tty_port *port, int raise);
};
struct tty_port {
struct tty_struct *tty; /* Back pointer */
const struct tty_port_operations *ops; /* Port operations */
spinlock_t lock; /* Lock protecting tty field */
int blocked_open; /* Waiting to open */
int count; /* Usage count */
wait_queue_head_t open_wait; /* Open waiters */
wait_queue_head_t close_wait; /* Close waiters */
unsigned long flags; /* TTY flags ASY_*/
struct mutex mutex; /* Locking */
unsigned char *xmit_buf; /* Optional buffer */
int close_delay; /* Close port delay */
int closing_wait; /* Delay for output */
int drain_delay; /* Set to zero if no pure time
based drain is needed else
set to size of fifo */
};
/*
* Where all of the state associated with a tty is kept while the tty
* is open. Since the termios state should be kept even if the tty
* has been closed --- for things like the baud rate, etc --- it is
* not stored here, but rather a pointer to the real state is stored
* here. Possible the winsize structure should have the same
* treatment, but (1) the default 80x24 is usually right and (2) it's
* most often used by a windowing system, which will set the correct
* size each time the window is created or resized anyway.
* - TYT, 9/14/92
*/
struct tty_operations;
struct tty_struct {
int magic;
struct kref kref;
struct tty_driver *driver;
const struct tty_operations *ops;
int index;
/* Protects ldisc changes: Lock tty not pty */
struct mutex ldisc_mutex;
struct tty_ldisc *ldisc;
struct mutex termios_mutex;
spinlock_t ctrl_lock;
/* Termios values are protected by the termios mutex */
struct ktermios *termios, *termios_locked;
struct termiox *termiox; /* May be NULL for unsupported */
char name[64];
struct pid *pgrp; /* Protected by ctrl lock */
struct pid *session;
unsigned long flags;
int count;
struct winsize winsize; /* termios mutex */
unsigned char stopped:1, hw_stopped:1, flow_stopped:1, packet:1;
unsigned char low_latency:1, warned:1;
unsigned char ctrl_status; /* ctrl_lock */
unsigned int receive_room; /* Bytes free for queue */
struct tty_struct *link;
struct fasync_struct *fasync;
struct tty_bufhead buf; /* Locked internally */
int alt_speed; /* For magic substitution of 38400 bps */
wait_queue_head_t write_wait;
wait_queue_head_t read_wait;
struct work_struct hangup_work;
void *disc_data;
void *driver_data;
struct list_head tty_files;
#define N_TTY_BUF_SIZE 4096
/*
* The following is data for the N_TTY line discipline. For
* historical reasons, this is included in the tty structure.
* Mostly locked by the BKL.
*/
unsigned int column;
unsigned char lnext:1, erasing:1, raw:1, real_raw:1, icanon:1;
unsigned char closing:1;
unsigned char echo_overrun:1;
unsigned short minimum_to_wake;
unsigned long overrun_time;
int num_overrun;
unsigned long process_char_map[256/(8*sizeof(unsigned long))];
char *read_buf;
int read_head;
int read_tail;
int read_cnt;
unsigned long read_flags[N_TTY_BUF_SIZE/(8*sizeof(unsigned long))];
unsigned char *echo_buf;
unsigned int echo_pos;
unsigned int echo_cnt;
int canon_data;
unsigned long canon_head;
unsigned int canon_column;
struct mutex atomic_read_lock;
struct mutex atomic_write_lock;
struct mutex output_lock;
struct mutex echo_lock;
unsigned char *write_buf;
int write_cnt;
spinlock_t read_lock;
/* If the tty has a pending do_SAK, queue it here - akpm */
struct work_struct SAK_work;
struct tty_port *port;
};
/* tty magic number */
#define TTY_MAGIC 0x5401
/*
* These bits are used in the flags field of the tty structure.
*
* So that interrupts won't be able to mess up the queues,
* copy_to_cooked must be atomic with respect to itself, as must
* tty->write. Thus, you must use the inline functions set_bit() and
* clear_bit() to make things atomic.
*/
#define TTY_THROTTLED 0 /* Call unthrottle() at threshold min */
#define TTY_IO_ERROR 1 /* Cause an I/O error (may be no ldisc too) */
#define TTY_OTHER_CLOSED 2 /* Other side (if any) has closed */
#define TTY_EXCLUSIVE 3 /* Exclusive open mode */
#define TTY_DEBUG 4 /* Debugging */
#define TTY_DO_WRITE_WAKEUP 5 /* Call write_wakeup after queuing new */
#define TTY_PUSH 6 /* n_tty private */
#define TTY_CLOSING 7 /* ->close() in progress */
#define TTY_LDISC 9 /* Line discipline attached */
#define TTY_LDISC_CHANGING 10 /* Line discipline changing */
#define TTY_LDISC_OPEN 11 /* Line discipline is open */
#define TTY_HW_COOK_OUT 14 /* Hardware can do output cooking */
#define TTY_HW_COOK_IN 15 /* Hardware can do input cooking */
#define TTY_PTY_LOCK 16 /* pty private */
#define TTY_NO_WRITE_SPLIT 17 /* Preserve write boundaries to driver */
#define TTY_HUPPED 18 /* Post driver->hangup() */
#define TTY_FLUSHING 19 /* Flushing to ldisc in progress */
#define TTY_FLUSHPENDING 20 /* Queued buffer flush pending */
#define TTY_WRITE_FLUSH(tty) tty_write_flush((tty))
extern void tty_write_flush(struct tty_struct *);
extern struct ktermios tty_std_termios;
extern int kmsg_redirect;
extern void console_init(void);
extern int vcs_init(void);
extern struct class *tty_class;
/**
* tty_kref_get - get a tty reference
* @tty: tty device
*
* Return a new reference to a tty object. The caller must hold
* sufficient locks/counts to ensure that their existing reference cannot
* go away
*/
static inline struct tty_struct *tty_kref_get(struct tty_struct *tty)
{
if (tty)
kref_get(&tty->kref);
return tty;
}
extern void tty_kref_put(struct tty_struct *tty);
extern int tty_paranoia_check(struct tty_struct *tty, struct inode *inode,
const char *routine);
extern char *tty_name(struct tty_struct *tty, char *buf);
extern void tty_wait_until_sent(struct tty_struct *tty, long timeout);
extern int tty_check_change(struct tty_struct *tty);
extern void stop_tty(struct tty_struct *tty);
extern void start_tty(struct tty_struct *tty);
extern int tty_register_driver(struct tty_driver *driver);
extern int tty_unregister_driver(struct tty_driver *driver);
extern struct device *tty_register_device(struct tty_driver *driver,
unsigned index, struct device *dev);
extern void tty_unregister_device(struct tty_driver *driver, unsigned index);
extern int tty_read_raw_data(struct tty_struct *tty, unsigned char *bufp,
int buflen);
extern void tty_write_message(struct tty_struct *tty, char *msg);
extern int tty_put_char(struct tty_struct *tty, unsigned char c);
extern int tty_chars_in_buffer(struct tty_struct *tty);
extern int tty_write_room(struct tty_struct *tty);
extern void tty_driver_flush_buffer(struct tty_struct *tty);
extern void tty_throttle(struct tty_struct *tty);
extern void tty_unthrottle(struct tty_struct *tty);
extern int tty_do_resize(struct tty_struct *tty, struct winsize *ws);
extern void tty_shutdown(struct tty_struct *tty);
extern void tty_free_termios(struct tty_struct *tty);
extern int is_current_pgrp_orphaned(void);
extern struct pid *tty_get_pgrp(struct tty_struct *tty);
extern int is_ignored(int sig);
extern int tty_signal(int sig, struct tty_struct *tty);
extern void tty_hangup(struct tty_struct *tty);
extern void tty_vhangup(struct tty_struct *tty);
extern void tty_vhangup_self(void);
extern void tty_unhangup(struct file *filp);
extern int tty_hung_up_p(struct file *filp);
extern void do_SAK(struct tty_struct *tty);
extern void __do_SAK(struct tty_struct *tty);
extern void disassociate_ctty(int priv);
extern void no_tty(void);
extern void tty_flip_buffer_push(struct tty_struct *tty);
extern void tty_buffer_free_all(struct tty_struct *tty);
extern void tty_buffer_flush(struct tty_struct *tty);
extern void tty_buffer_init(struct tty_struct *tty);
extern speed_t tty_get_baud_rate(struct tty_struct *tty);
extern speed_t tty_termios_baud_rate(struct ktermios *termios);
extern speed_t tty_termios_input_baud_rate(struct ktermios *termios);
extern void tty_termios_encode_baud_rate(struct ktermios *termios,
speed_t ibaud, speed_t obaud);
extern void tty_encode_baud_rate(struct tty_struct *tty,
speed_t ibaud, speed_t obaud);
extern void tty_termios_copy_hw(struct ktermios *new, struct ktermios *old);
extern int tty_termios_hw_change(struct ktermios *a, struct ktermios *b);
extern struct tty_ldisc *tty_ldisc_ref(struct tty_struct *);
extern void tty_ldisc_deref(struct tty_ldisc *);
extern struct tty_ldisc *tty_ldisc_ref_wait(struct tty_struct *);
extern void tty_ldisc_hangup(struct tty_struct *tty);
extern const struct file_operations tty_ldiscs_proc_fops;
extern void tty_wakeup(struct tty_struct *tty);
extern void tty_ldisc_flush(struct tty_struct *tty);
extern long tty_ioctl(struct file *file, unsigned int cmd, unsigned long arg);
extern int tty_mode_ioctl(struct tty_struct *tty, struct file *file,
unsigned int cmd, unsigned long arg);
extern int tty_perform_flush(struct tty_struct *tty, unsigned long arg);
extern dev_t tty_devnum(struct tty_struct *tty);
extern void proc_clear_tty(struct task_struct *p);
extern struct tty_struct *get_current_tty(void);
extern void tty_default_fops(struct file_operations *fops);
extern struct tty_struct *alloc_tty_struct(void);
extern void free_tty_struct(struct tty_struct *tty);
extern void initialize_tty_struct(struct tty_struct *tty,
struct tty_driver *driver, int idx);
extern struct tty_struct *tty_init_dev(struct tty_driver *driver, int idx,
int first_ok);
extern void tty_release_dev(struct file *filp);
extern int tty_init_termios(struct tty_struct *tty);
extern struct tty_struct *tty_pair_get_tty(struct tty_struct *tty);
extern struct tty_struct *tty_pair_get_pty(struct tty_struct *tty);
extern struct mutex tty_mutex;
extern void tty_write_unlock(struct tty_struct *tty);
extern int tty_write_lock(struct tty_struct *tty, int ndelay);
#define tty_is_writelocked(tty) (mutex_is_locked(&tty->atomic_write_lock))
extern void tty_port_init(struct tty_port *port);
extern int tty_port_alloc_xmit_buf(struct tty_port *port);
extern void tty_port_free_xmit_buf(struct tty_port *port);
extern struct tty_struct *tty_port_tty_get(struct tty_port *port);
extern void tty_port_tty_set(struct tty_port *port, struct tty_struct *tty);
extern int tty_port_carrier_raised(struct tty_port *port);
extern void tty_port_raise_dtr_rts(struct tty_port *port);
extern void tty_port_lower_dtr_rts(struct tty_port *port);
extern void tty_port_hangup(struct tty_port *port);
extern int tty_port_block_til_ready(struct tty_port *port,
struct tty_struct *tty, struct file *filp);
extern int tty_port_close_start(struct tty_port *port,
struct tty_struct *tty, struct file *filp);
extern void tty_port_close_end(struct tty_port *port, struct tty_struct *tty);
extern int tty_register_ldisc(int disc, struct tty_ldisc_ops *new_ldisc);
extern int tty_unregister_ldisc(int disc);
extern int tty_set_ldisc(struct tty_struct *tty, int ldisc);
extern int tty_ldisc_setup(struct tty_struct *tty, struct tty_struct *o_tty);
extern void tty_ldisc_release(struct tty_struct *tty, struct tty_struct *o_tty);
extern void tty_ldisc_init(struct tty_struct *tty);
extern void tty_ldisc_begin(void);
/* This last one is just for the tty layer internals and shouldn't be used elsewhere */
extern void tty_ldisc_enable(struct tty_struct *tty);
/* n_tty.c */
extern struct tty_ldisc_ops tty_ldisc_N_TTY;
/* tty_audit.c */
#ifdef CONFIG_AUDIT
extern void tty_audit_add_data(struct tty_struct *tty, unsigned char *data,
size_t size);
extern void tty_audit_exit(void);
extern void tty_audit_fork(struct signal_struct *sig);
extern void tty_audit_tiocsti(struct tty_struct *tty, char ch);
extern void tty_audit_push(struct tty_struct *tty);
extern void tty_audit_push_task(struct task_struct *tsk,
uid_t loginuid, u32 sessionid);
#else
static inline void tty_audit_add_data(struct tty_struct *tty,
unsigned char *data, size_t size)
{
}
static inline void tty_audit_tiocsti(struct tty_struct *tty, char ch)
{
}
static inline void tty_audit_exit(void)
{
}
static inline void tty_audit_fork(struct signal_struct *sig)
{
}
static inline void tty_audit_push(struct tty_struct *tty)
{
}
static inline void tty_audit_push_task(struct task_struct *tsk,
uid_t loginuid, u32 sessionid)
{
}
#endif
/* tty_ioctl.c */
extern int n_tty_ioctl_helper(struct tty_struct *tty, struct file *file,
unsigned int cmd, unsigned long arg);
/* serial.c */
extern void serial_console_init(void);
/* pcxx.c */
extern int pcxe_open(struct tty_struct *tty, struct file *filp);
/* printk.c */
extern void console_print(const char *);
/* vt.c */
extern int vt_ioctl(struct tty_struct *tty, struct file *file,
unsigned int cmd, unsigned long arg);
#endif /* __KERNEL__ */
#endif
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