From 31d1d48e199e99077fb30f6fb9a793be7bec756f Mon Sep 17 00:00:00 2001 From: David Howells Date: Fri, 6 Aug 2010 16:34:43 +0100 Subject: Fix init ordering of /dev/console vs callers of modprobe Make /dev/console get initialised before any initialisation routine that invokes modprobe because if modprobe fails, it's going to want to open /dev/console, presumably to write an error message to. The problem with that is that if the /dev/console driver is not yet initialised, the chardev handler will call request_module() to invoke modprobe, which will fail, because we never compile /dev/console as a module. This will lead to a modprobe loop, showing the following in the kernel log: request_module: runaway loop modprobe char-major-5-1 request_module: runaway loop modprobe char-major-5-1 request_module: runaway loop modprobe char-major-5-1 request_module: runaway loop modprobe char-major-5-1 request_module: runaway loop modprobe char-major-5-1 This can happen, for example, when the built in md5 module can't find the built in cryptomgr module (because the latter fails to initialise). The md5 module comes before the call to tty_init(), presumably because 'crypto' comes before 'drivers' alphabetically. Fix this by calling tty_init() from chrdev_init(). Signed-off-by: David Howells Signed-off-by: Linus Torvalds --- include/linux/tty.h | 3 +++ 1 file changed, 3 insertions(+) (limited to 'include/linux/tty.h') diff --git a/include/linux/tty.h b/include/linux/tty.h index 931078b73226..7802a243ee13 100644 --- a/include/linux/tty.h +++ b/include/linux/tty.h @@ -552,6 +552,9 @@ static inline void tty_audit_push_task(struct task_struct *tsk, } #endif +/* tty_io.c */ +extern int __init tty_init(void); + /* tty_ioctl.c */ extern int n_tty_ioctl_helper(struct tty_struct *tty, struct file *file, unsigned int cmd, unsigned long arg); -- cgit v1.2.3 From 26df6d13406d1a53b0bda08bd712f1924affd7cd Mon Sep 17 00:00:00 2001 From: "hyc@symas.com" Date: Tue, 22 Jun 2010 10:14:49 -0700 Subject: tty: Add EXTPROC support for LINEMODE This patch is against the 2.6.34 source. Paraphrased from the 1989 BSD patch by David Borman @ cray.com: These are the changes needed for the kernel to support LINEMODE in the server. There is a new bit in the termios local flag word, EXTPROC. When this bit is set, several aspects of the terminal driver are disabled. Input line editing, character echo, and mapping of signals are all disabled. This allows the telnetd to turn off these functions when in linemode, but still keep track of what state the user wants the terminal to be in. New ioctl: TIOCSIG Generate a signal to processes in the current process group of the pty. There is a new mode for packet driver, the TIOCPKT_IOCTL bit. When packet mode is turned on in the pty, and the EXTPROC bit is set, then whenever the state of the pty is changed, the next read on the master side of the pty will have the TIOCPKT_IOCTL bit set. This allows the process on the server side of the pty to know when the state of the terminal has changed; it can then issue the appropriate ioctl to retrieve the new state. Since the original BSD patches accompanied the source code for telnet I've left that reference here, but obviously the feature is useful for any remote terminal protocol, including ssh. The corresponding feature has existed in the BSD tty driver since 1989. For historical reference, a good copy of the relevant files can be found here: http://anonsvn.mit.edu/viewvc/krb5/trunk/src/appl/telnet/?pathrev=17741 Signed-off-by: Howard Chu Cc: Alan Cox Signed-off-by: Greg Kroah-Hartman --- include/linux/tty.h | 1 + 1 file changed, 1 insertion(+) (limited to 'include/linux/tty.h') diff --git a/include/linux/tty.h b/include/linux/tty.h index 7802a243ee13..2df60e4ff40e 100644 --- a/include/linux/tty.h +++ b/include/linux/tty.h @@ -179,6 +179,7 @@ struct tty_bufhead { #define L_FLUSHO(tty) _L_FLAG((tty), FLUSHO) #define L_PENDIN(tty) _L_FLAG((tty), PENDIN) #define L_IEXTEN(tty) _L_FLAG((tty), IEXTEN) +#define L_EXTPROC(tty) _L_FLAG((tty), EXTPROC) struct device; struct signal_struct; -- cgit v1.2.3 From ec79d6056de58511d8e46d9ae59d3878f958dc3e Mon Sep 17 00:00:00 2001 From: Arnd Bergmann Date: Tue, 1 Jun 2010 22:53:01 +0200 Subject: tty: replace BKL with a new tty_lock As a preparation for replacing the big kernel lock in the TTY layer, wrap all the callers in new macros tty_lock, tty_lock_nested and tty_unlock. Signed-off-by: Arnd Bergmann Cc: Alan Cox Signed-off-by: Greg Kroah-Hartman --- include/linux/tty.h | 31 +++++++++++++++++++++++++++++++ 1 file changed, 31 insertions(+) (limited to 'include/linux/tty.h') diff --git a/include/linux/tty.h b/include/linux/tty.h index 2df60e4ff40e..6ead6b60c743 100644 --- a/include/linux/tty.h +++ b/include/linux/tty.h @@ -13,6 +13,7 @@ #include #include #include +#include #include @@ -576,5 +577,35 @@ extern int vt_ioctl(struct tty_struct *tty, struct file *file, extern long vt_compat_ioctl(struct tty_struct *tty, struct file * file, unsigned int cmd, unsigned long arg); +/* functions for preparation of BKL removal */ + +/* + * tty_lock_nested get the tty_lock while potentially holding it + * + * The Big TTY Mutex is a recursive lock, meaning you can take it + * from a thread that is already holding it. + * This is bad for a number of reasons, so tty_lock_nested should + * really be used as rarely as possible. If a code location can + * be shown to never get called with this held already, it should + * use tty_lock() instead. + */ +static inline void __lockfunc tty_lock_nested(void) __acquires(kernel_lock) +{ + lock_kernel(); +} +static inline void tty_lock(void) __acquires(kernel_lock) +{ +#ifdef CONFIG_LOCK_KERNEL + /* kernel_locked is 1 for !CONFIG_LOCK_KERNEL */ + WARN_ON(kernel_locked()); +#endif + lock_kernel(); +} +static inline void tty_unlock(void) __releases(kernel_lock) +{ + unlock_kernel(); +} +#define tty_locked() (kernel_locked()) + #endif /* __KERNEL__ */ #endif -- cgit v1.2.3 From be1bc2889a4db4961ef69f47fb471ecae9f23ade Mon Sep 17 00:00:00 2001 From: Arnd Bergmann Date: Tue, 1 Jun 2010 22:53:05 +0200 Subject: tty: introduce wait_event_interruptible_tty Calling wait_event_interruptible implicitly releases the BKL when it sleeps, but we need to do this explcitly when we have converted it to a mutex. Signed-off-by: Arnd Bergmann Cc: Alan Cox Signed-off-by: Greg Kroah-Hartman --- include/linux/tty.h | 42 ++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 42 insertions(+) (limited to 'include/linux/tty.h') diff --git a/include/linux/tty.h b/include/linux/tty.h index 6ead6b60c743..955d72ea71c0 100644 --- a/include/linux/tty.h +++ b/include/linux/tty.h @@ -607,5 +607,47 @@ static inline void tty_unlock(void) __releases(kernel_lock) } #define tty_locked() (kernel_locked()) +/* + * wait_event_interruptible_tty -- wait for a condition with the tty lock held + * + * The condition we are waiting for might take a long time to + * become true, or might depend on another thread taking the + * BTM. In either case, we need to drop the BTM to guarantee + * forward progress. This is a leftover from the conversion + * from the BKL and should eventually get removed as the BTM + * falls out of use. + * + * Do not use in new code. + */ +#define wait_event_interruptible_tty(wq, condition) \ +({ \ + int __ret = 0; \ + if (!(condition)) { \ + __wait_event_interruptible_tty(wq, condition, __ret); \ + } \ + __ret; \ +}) + +#define __wait_event_interruptible_tty(wq, condition, ret) \ +do { \ + DEFINE_WAIT(__wait); \ + \ + for (;;) { \ + prepare_to_wait(&wq, &__wait, TASK_INTERRUPTIBLE); \ + if (condition) \ + break; \ + if (!signal_pending(current)) { \ + tty_unlock(); \ + schedule(); \ + tty_lock(); \ + continue; \ + } \ + ret = -ERESTARTSYS; \ + break; \ + } \ + finish_wait(&wq, &__wait); \ +} while (0) + + #endif /* __KERNEL__ */ #endif -- cgit v1.2.3 From ddcd9fb66ae7f448b517242c10a31d4e17bcad45 Mon Sep 17 00:00:00 2001 From: Arnd Bergmann Date: Tue, 1 Jun 2010 22:53:08 +0200 Subject: tty: remove tty_lock_nested This changes all remaining users of tty_lock_nested to be non-recursive, which lets us kill this function. As a consequence, we won't need to keep the lock count any more, which allows more simplifications later. Signed-off-by: Arnd Bergmann Cc: Alan Cox Signed-off-by: Greg Kroah-Hartman --- include/linux/tty.h | 16 +--------------- 1 file changed, 1 insertion(+), 15 deletions(-) (limited to 'include/linux/tty.h') diff --git a/include/linux/tty.h b/include/linux/tty.h index 955d72ea71c0..0fbafb0b69bf 100644 --- a/include/linux/tty.h +++ b/include/linux/tty.h @@ -417,6 +417,7 @@ 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_locked(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); @@ -578,21 +579,6 @@ extern long vt_compat_ioctl(struct tty_struct *tty, struct file * file, unsigned int cmd, unsigned long arg); /* functions for preparation of BKL removal */ - -/* - * tty_lock_nested get the tty_lock while potentially holding it - * - * The Big TTY Mutex is a recursive lock, meaning you can take it - * from a thread that is already holding it. - * This is bad for a number of reasons, so tty_lock_nested should - * really be used as rarely as possible. If a code location can - * be shown to never get called with this held already, it should - * use tty_lock() instead. - */ -static inline void __lockfunc tty_lock_nested(void) __acquires(kernel_lock) -{ - lock_kernel(); -} static inline void tty_lock(void) __acquires(kernel_lock) { #ifdef CONFIG_LOCK_KERNEL -- cgit v1.2.3 From b07471fa51358ce64cc25e1501544502362e4404 Mon Sep 17 00:00:00 2001 From: Arnd Bergmann Date: Fri, 6 Aug 2010 21:40:30 +0200 Subject: tty: implement BTM as mutex instead of BKL The tty locking now follows the rules for mutexes, so we can replace the BKL usage with a new subsystem wide mutex. Using a regular mutex here will change the behaviour when blocked on the BTM from spinning to sleeping, but that should not be visible to the user. Using the mutex also means that all the BTM is now covered by lockdep. Signed-off-by: Arnd Bergmann Cc: Alan Cox Signed-off-by: Greg Kroah-Hartman --- include/linux/tty.h | 18 +++++------------- 1 file changed, 5 insertions(+), 13 deletions(-) (limited to 'include/linux/tty.h') diff --git a/include/linux/tty.h b/include/linux/tty.h index 0fbafb0b69bf..1437da3ddc62 100644 --- a/include/linux/tty.h +++ b/include/linux/tty.h @@ -578,20 +578,12 @@ extern int vt_ioctl(struct tty_struct *tty, struct file *file, extern long vt_compat_ioctl(struct tty_struct *tty, struct file * file, unsigned int cmd, unsigned long arg); +/* tty_mutex.c */ /* functions for preparation of BKL removal */ -static inline void tty_lock(void) __acquires(kernel_lock) -{ -#ifdef CONFIG_LOCK_KERNEL - /* kernel_locked is 1 for !CONFIG_LOCK_KERNEL */ - WARN_ON(kernel_locked()); -#endif - lock_kernel(); -} -static inline void tty_unlock(void) __releases(kernel_lock) -{ - unlock_kernel(); -} -#define tty_locked() (kernel_locked()) +extern void __lockfunc tty_lock(void) __acquires(tty_lock); +extern void __lockfunc tty_unlock(void) __releases(tty_lock); +extern struct task_struct *__big_tty_mutex_owner; +#define tty_locked() (current == __big_tty_mutex_owner) /* * wait_event_interruptible_tty -- wait for a condition with the tty lock held -- cgit v1.2.3