mirror of
https://github.com/team-infusion-developers/android_kernel_samsung_msm8976.git
synced 2024-10-31 18:09:19 +00:00
e2034cb826
Line discipline locking was performed with a combination of
a mutex, a status bit, a count, and a waitqueue -- basically,
a rw semaphore.
Replace the existing combination with an ld_semaphore.
Fixes:
1) the 'reference acquire after ldisc locked' bug
2) the over-complicated halt mechanism
3) lock order wrt. tty_lock()
4) dropping locks while changing ldisc
5) previously unidentified deadlock while locking ldisc from
both linked ttys concurrently
6) previously unidentified recursive deadlocks
Adds much-needed lockdep diagnostics.
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Git-commit: 36697529b5bbe36911e39a6309e7a7c9250d280a
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
Signed-off-by: Osvaldo Banuelos <osvaldob@codeaurora.org>
210 lines
7 KiB
C
210 lines
7 KiB
C
#ifndef _LINUX_TTY_LDISC_H
|
|
#define _LINUX_TTY_LDISC_H
|
|
|
|
/*
|
|
* This structure defines the interface between the tty line discipline
|
|
* implementation and the tty routines. The following routines can be
|
|
* defined; unless noted otherwise, they are optional, and can be
|
|
* filled in with a null pointer.
|
|
*
|
|
* int (*open)(struct tty_struct *);
|
|
*
|
|
* This function is called when the line discipline is associated
|
|
* with the tty. The line discipline can use this as an
|
|
* opportunity to initialize any state needed by the ldisc routines.
|
|
*
|
|
* void (*close)(struct tty_struct *);
|
|
*
|
|
* This function is called when the line discipline is being
|
|
* shutdown, either because the tty is being closed or because
|
|
* the tty is being changed to use a new line discipline
|
|
*
|
|
* void (*flush_buffer)(struct tty_struct *tty);
|
|
*
|
|
* This function instructs the line discipline to clear its
|
|
* buffers of any input characters it may have queued to be
|
|
* delivered to the user mode process.
|
|
*
|
|
* ssize_t (*chars_in_buffer)(struct tty_struct *tty);
|
|
*
|
|
* This function returns the number of input characters the line
|
|
* discipline may have queued up to be delivered to the user mode
|
|
* process.
|
|
*
|
|
* ssize_t (*read)(struct tty_struct * tty, struct file * file,
|
|
* unsigned char * buf, size_t nr);
|
|
*
|
|
* This function is called when the user requests to read from
|
|
* the tty. The line discipline will return whatever characters
|
|
* it has buffered up for the user. If this function is not
|
|
* defined, the user will receive an EIO error.
|
|
*
|
|
* ssize_t (*write)(struct tty_struct * tty, struct file * file,
|
|
* const unsigned char * buf, size_t nr);
|
|
*
|
|
* This function is called when the user requests to write to the
|
|
* tty. The line discipline will deliver the characters to the
|
|
* low-level tty device for transmission, optionally performing
|
|
* some processing on the characters first. If this function is
|
|
* not defined, the user will receive an EIO error.
|
|
*
|
|
* int (*ioctl)(struct tty_struct * tty, struct file * file,
|
|
* unsigned int cmd, unsigned long arg);
|
|
*
|
|
* This function is called when the user requests an ioctl which
|
|
* is not handled by the tty layer or the low-level tty driver.
|
|
* It is intended for ioctls which affect line discpline
|
|
* operation. Note that the search order for ioctls is (1) tty
|
|
* layer, (2) tty low-level driver, (3) line discpline. So a
|
|
* low-level driver can "grab" an ioctl request before the line
|
|
* discpline has a chance to see it.
|
|
*
|
|
* long (*compat_ioctl)(struct tty_struct * tty, struct file * file,
|
|
* unsigned int cmd, unsigned long arg);
|
|
*
|
|
* Process ioctl calls from 32-bit process on 64-bit system
|
|
*
|
|
* void (*set_termios)(struct tty_struct *tty, struct ktermios * old);
|
|
*
|
|
* This function notifies the line discpline that a change has
|
|
* been made to the termios structure.
|
|
*
|
|
* int (*poll)(struct tty_struct * tty, struct file * file,
|
|
* poll_table *wait);
|
|
*
|
|
* This function is called when a user attempts to select/poll on a
|
|
* tty device. It is solely the responsibility of the line
|
|
* discipline to handle poll requests.
|
|
*
|
|
* void (*receive_buf)(struct tty_struct *, const unsigned char *cp,
|
|
* char *fp, int count);
|
|
*
|
|
* This function is called by the low-level tty driver to send
|
|
* characters received by the hardware to the line discpline for
|
|
* processing. <cp> is a pointer to the buffer of input
|
|
* character received by the device. <fp> is a pointer to a
|
|
* pointer of flag bytes which indicate whether a character was
|
|
* received with a parity error, etc.
|
|
*
|
|
* void (*write_wakeup)(struct tty_struct *);
|
|
*
|
|
* This function is called by the low-level tty driver to signal
|
|
* that line discpline should try to send more characters to the
|
|
* low-level driver for transmission. If the line discpline does
|
|
* not have any more data to send, it can just return.
|
|
*
|
|
* int (*hangup)(struct tty_struct *)
|
|
*
|
|
* Called on a hangup. Tells the discipline that it should
|
|
* cease I/O to the tty driver. Can sleep. The driver should
|
|
* seek to perform this action quickly but should wait until
|
|
* any pending driver I/O is completed.
|
|
*
|
|
* void (*dcd_change)(struct tty_struct *tty, unsigned int status)
|
|
*
|
|
* Tells the discipline that the DCD pin has changed its status.
|
|
* Used exclusively by the N_PPS (Pulse-Per-Second) line discipline.
|
|
*/
|
|
|
|
#include <linux/fs.h>
|
|
#include <linux/wait.h>
|
|
#include <linux/wait.h>
|
|
|
|
|
|
/*
|
|
* the semaphore definition
|
|
*/
|
|
struct ld_semaphore {
|
|
long count;
|
|
raw_spinlock_t wait_lock;
|
|
unsigned int wait_readers;
|
|
struct list_head read_wait;
|
|
struct list_head write_wait;
|
|
#ifdef CONFIG_DEBUG_LOCK_ALLOC
|
|
struct lockdep_map dep_map;
|
|
#endif
|
|
};
|
|
|
|
extern void __init_ldsem(struct ld_semaphore *sem, const char *name,
|
|
struct lock_class_key *key);
|
|
|
|
#define init_ldsem(sem) \
|
|
do { \
|
|
static struct lock_class_key __key; \
|
|
\
|
|
__init_ldsem((sem), #sem, &__key); \
|
|
} while (0)
|
|
|
|
|
|
extern int ldsem_down_read(struct ld_semaphore *sem, long timeout);
|
|
extern int ldsem_down_read_trylock(struct ld_semaphore *sem);
|
|
extern int ldsem_down_write(struct ld_semaphore *sem, long timeout);
|
|
extern int ldsem_down_write_trylock(struct ld_semaphore *sem);
|
|
extern void ldsem_up_read(struct ld_semaphore *sem);
|
|
extern void ldsem_up_write(struct ld_semaphore *sem);
|
|
|
|
#ifdef CONFIG_DEBUG_LOCK_ALLOC
|
|
extern int ldsem_down_read_nested(struct ld_semaphore *sem, int subclass,
|
|
long timeout);
|
|
extern int ldsem_down_write_nested(struct ld_semaphore *sem, int subclass,
|
|
long timeout);
|
|
#else
|
|
# define ldsem_down_read_nested(sem, subclass, timeout) \
|
|
ldsem_down_read(sem, timeout)
|
|
# define ldsem_down_write_nested(sem, subclass, timeout) \
|
|
ldsem_down_write(sem, timeout)
|
|
#endif
|
|
|
|
|
|
struct tty_ldisc_ops {
|
|
int magic;
|
|
char *name;
|
|
int num;
|
|
int flags;
|
|
|
|
/*
|
|
* The following routines are called from above.
|
|
*/
|
|
int (*open)(struct tty_struct *);
|
|
void (*close)(struct tty_struct *);
|
|
void (*flush_buffer)(struct tty_struct *tty);
|
|
ssize_t (*chars_in_buffer)(struct tty_struct *tty);
|
|
ssize_t (*read)(struct tty_struct *tty, struct file *file,
|
|
unsigned char __user *buf, size_t nr);
|
|
ssize_t (*write)(struct tty_struct *tty, struct file *file,
|
|
const unsigned char *buf, size_t nr);
|
|
int (*ioctl)(struct tty_struct *tty, struct file *file,
|
|
unsigned int cmd, unsigned long arg);
|
|
long (*compat_ioctl)(struct tty_struct *tty, struct file *file,
|
|
unsigned int cmd, unsigned long arg);
|
|
void (*set_termios)(struct tty_struct *tty, struct ktermios *old);
|
|
unsigned int (*poll)(struct tty_struct *, struct file *,
|
|
struct poll_table_struct *);
|
|
int (*hangup)(struct tty_struct *tty);
|
|
|
|
/*
|
|
* The following routines are called from below.
|
|
*/
|
|
void (*receive_buf)(struct tty_struct *, const unsigned char *cp,
|
|
char *fp, int count);
|
|
void (*write_wakeup)(struct tty_struct *);
|
|
void (*dcd_change)(struct tty_struct *, unsigned int);
|
|
|
|
struct module *owner;
|
|
|
|
int refcount;
|
|
};
|
|
|
|
struct tty_ldisc {
|
|
struct tty_ldisc_ops *ops;
|
|
struct tty_struct *tty;
|
|
};
|
|
|
|
#define TTY_LDISC_MAGIC 0x5403
|
|
|
|
#define LDISC_FLAG_DEFINED 0x00000001
|
|
|
|
#define MODULE_ALIAS_LDISC(ldisc) \
|
|
MODULE_ALIAS("tty-ldisc-" __stringify(ldisc))
|
|
|
|
#endif /* _LINUX_TTY_LDISC_H */
|