d79a580936
Clean up the console driver locking. There are various problems here, including sleeping under a spinlock and spinlock recursion, some of which are fixed here. This patch deals with the locking involved with opens and closes. The problem is that an mconsole request to change a console's configuration can race with an open. Changing a configuration should only be done when a console isn't opened. Also, an open must be looking at a stable configuration. In addition, a get configuration request must observe the same locking since it must also see a stable configuration. With the old locking, it was possible for this to hang indefinitely in some cases because open would block for a long time waiting for a connection from the host while holding the lock needed by the mconsole request. As explained in the long comment, this is fixed by adding a spinlock for the use count and configuration and a mutex for the actual open and close. Signed-off-by: Jeff Dike <jdike@addtoit.com> Cc: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
113 lines
3.2 KiB
C
113 lines
3.2 KiB
C
/*
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* Copyright (C) 2001, 2002 Jeff Dike (jdike@karaya.com)
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* Licensed under the GPL
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*/
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#ifndef __LINE_H__
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#define __LINE_H__
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#include "linux/list.h"
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#include "linux/workqueue.h"
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#include "linux/tty.h"
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#include "linux/interrupt.h"
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#include "linux/spinlock.h"
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#include "linux/mutex.h"
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#include "chan_user.h"
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#include "mconsole_kern.h"
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struct line_driver {
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char *name;
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char *device_name;
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short major;
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short minor_start;
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short type;
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short subtype;
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int read_irq;
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char *read_irq_name;
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int write_irq;
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char *write_irq_name;
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char *symlink_from;
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char *symlink_to;
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struct mc_device mc;
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};
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struct line {
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struct tty_struct *tty;
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spinlock_t count_lock;
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int valid;
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struct mutex open_mutex;
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char *init_str;
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int init_pri;
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struct list_head chan_list;
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/*This lock is actually, mostly, local to*/
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spinlock_t lock;
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int throttled;
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/* Yes, this is a real circular buffer.
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* XXX: And this should become a struct kfifo!
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*
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* buffer points to a buffer allocated on demand, of length
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* LINE_BUFSIZE, head to the start of the ring, tail to the end.*/
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char *buffer;
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char *head;
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char *tail;
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int sigio;
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struct delayed_work task;
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const struct line_driver *driver;
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int have_irq;
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};
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#define LINE_INIT(str, d) \
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{ .count_lock = SPIN_LOCK_UNLOCKED, \
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.init_str = str, \
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.init_pri = INIT_STATIC, \
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.valid = 1, \
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.lock = SPIN_LOCK_UNLOCKED, \
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.driver = d }
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struct lines {
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int num;
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};
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#define LINES_INIT(n) { .num = n }
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extern void line_close(struct tty_struct *tty, struct file * filp);
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extern int line_open(struct line *lines, struct tty_struct *tty);
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extern int line_setup(struct line *lines, unsigned int sizeof_lines,
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char *init);
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extern int line_write(struct tty_struct *tty, const unsigned char *buf,
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int len);
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extern void line_put_char(struct tty_struct *tty, unsigned char ch);
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extern void line_set_termios(struct tty_struct *tty, struct ktermios * old);
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extern int line_chars_in_buffer(struct tty_struct *tty);
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extern void line_flush_buffer(struct tty_struct *tty);
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extern void line_flush_chars(struct tty_struct *tty);
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extern int line_write_room(struct tty_struct *tty);
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extern int line_ioctl(struct tty_struct *tty, struct file * file,
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unsigned int cmd, unsigned long arg);
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extern void line_throttle(struct tty_struct *tty);
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extern void line_unthrottle(struct tty_struct *tty);
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extern char *add_xterm_umid(char *base);
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extern int line_setup_irq(int fd, int input, int output, struct line *line,
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void *data);
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extern void line_close_chan(struct line *line);
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extern struct tty_driver * line_register_devfs(struct lines *set,
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struct line_driver *line_driver,
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const struct tty_operations *driver,
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struct line *lines, int nlines);
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extern void lines_init(struct line *lines, int nlines, struct chan_opts *opts);
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extern void close_lines(struct line *lines, int nlines);
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extern int line_config(struct line *lines, unsigned int sizeof_lines,
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char *str, const struct chan_opts *opts);
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extern int line_id(char **str, int *start_out, int *end_out);
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extern int line_remove(struct line *lines, unsigned int sizeof_lines, int n);
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extern int line_get_config(char *dev, struct line *lines,
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unsigned int sizeof_lines, char *str,
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int size, char **error_out);
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#endif
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