From 79c1faa4511e78380cd643dac88a775062a08bc0 Mon Sep 17 00:00:00 2001 From: Peter Hurley Date: Sat, 10 Oct 2015 16:00:51 -0400 Subject: tty: Remove tty_wait_until_sent_from_close() tty_wait_until_sent_from_close() drops the tty lock while waiting for the tty driver to finish sending previously accepted data (ie., data remaining in its write buffer and transmit fifo). tty_wait_until_sent_from_close() was added by commit a57a7bf3fc7e ("TTY: define tty_wait_until_sent_from_close") to prevent the entire tty subsystem from being unable to open new ttys while waiting for one tty to close while output drained. However, since commit 0911261d4cb6 ("tty: Don't take tty_mutex for tty count changes"), holding a tty lock while closing does not prevent other ttys from being opened/closed/hung up, but only prevents lifetime event changes for the tty under lock. Holding the tty lock while waiting for output to drain does prevent parallel non-blocking opens (O_NONBLOCK) from advancing or returning while the tty lock is held. However, all parallel opens _already_ block even if the tty lock is dropped while closing and the parallel open advances. Blocking in open has been in mainline since at least 2.6.29 (see tty_port_block_til_ready(); note the test for O_NONBLOCK is _after_ the wait while ASYNC_CLOSING). IOW, before this patch a non-blocking open will sleep anyway for the _entire_ duration of a parallel hardware shutdown, and when it wakes, the error return will cause a release of its tty, and it will restart with a fresh attempt to open. Similarly with a blocking open that is already waiting; when it's woken, the hardware shutdown has already completed to ASYNC_INITIALIZED is not set, which forces a release and restart as well. So, holding the tty lock across the _entire_ close (which is what this patch does), even while waiting for output to drain, is equivalent to the current outcome wrt parallel opens. Cc: Alan Cox Cc: David Laight CC: Arnd Bergmann CC: Karsten Keil CC: linuxppc-dev@lists.ozlabs.org Signed-off-by: Peter Hurley Signed-off-by: Greg Kroah-Hartman --- include/linux/tty.h | 18 ------------------ 1 file changed, 18 deletions(-) (limited to 'include/linux/tty.h') diff --git a/include/linux/tty.h b/include/linux/tty.h index d072ded41678..614c8224c32f 100644 --- a/include/linux/tty.h +++ b/include/linux/tty.h @@ -656,24 +656,6 @@ extern void __lockfunc tty_unlock(struct tty_struct *tty); extern void __lockfunc tty_lock_slave(struct tty_struct *tty); extern void __lockfunc tty_unlock_slave(struct tty_struct *tty); extern void tty_set_lock_subclass(struct tty_struct *tty); -/* - * this shall be called only from where BTM is held (like close) - * - * We need this to ensure nobody waits for us to finish while we are waiting. - * Without this we were encountering system stalls. - * - * This should be indeed removed with BTM removal later. - * - * Locking: BTM required. Nobody is allowed to hold port->mutex. - */ -static inline void tty_wait_until_sent_from_close(struct tty_struct *tty, - long timeout) -{ - tty_unlock(tty); /* tty->ops->close holds the BTM, drop it while waiting */ - tty_wait_until_sent(tty, timeout); - tty_lock(tty); -} - /* * wait_event_interruptible_tty -- wait for a condition with the tty lock held * -- cgit v1.2.3 From cc2aaabfd6d6335e2156781ca67715b4de17f993 Mon Sep 17 00:00:00 2001 From: Peter Hurley Date: Sat, 10 Oct 2015 16:00:54 -0400 Subject: tty: Remove tty_port::close_wait With the removal of tty_wait_until_sent_from_close(), tty drivers no longer wait during open for parallel closes to complete (instead, the tty core waits before calling the driver open() method). Thus, the close_wait waitqueue is no longer used for waiting. Remove struct tty_port::close_wait. Signed-off-by: Peter Hurley Signed-off-by: Greg Kroah-Hartman --- include/linux/tty.h | 1 - 1 file changed, 1 deletion(-) (limited to 'include/linux/tty.h') diff --git a/include/linux/tty.h b/include/linux/tty.h index 614c8224c32f..090ce2a52262 100644 --- a/include/linux/tty.h +++ b/include/linux/tty.h @@ -227,7 +227,6 @@ struct tty_port { 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 */ wait_queue_head_t delta_msr_wait; /* Modem status change */ unsigned long flags; /* TTY flags ASY_*/ unsigned char console:1, /* port is a console */ -- cgit v1.2.3 From f148d6d7b79adb42a8e7fa95bf6be5b607015f26 Mon Sep 17 00:00:00 2001 From: Peter Hurley Date: Sat, 10 Oct 2015 16:00:57 -0400 Subject: tty: Remove wait_event_interruptible_tty() In-tree users of wait_event_interruptible_tty() have been removed; remove. Signed-off-by: Peter Hurley Signed-off-by: Greg Kroah-Hartman --- include/linux/tty.h | 26 -------------------------- 1 file changed, 26 deletions(-) (limited to 'include/linux/tty.h') diff --git a/include/linux/tty.h b/include/linux/tty.h index 090ce2a52262..c2889f4331e1 100644 --- a/include/linux/tty.h +++ b/include/linux/tty.h @@ -655,32 +655,6 @@ extern void __lockfunc tty_unlock(struct tty_struct *tty); extern void __lockfunc tty_lock_slave(struct tty_struct *tty); extern void __lockfunc tty_unlock_slave(struct tty_struct *tty); extern void tty_set_lock_subclass(struct tty_struct *tty); -/* - * 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(tty, wq, condition) \ -({ \ - int __ret = 0; \ - if (!(condition)) \ - __ret = __wait_event_interruptible_tty(tty, wq, \ - condition); \ - __ret; \ -}) - -#define __wait_event_interruptible_tty(tty, wq, condition) \ - ___wait_event(wq, condition, TASK_INTERRUPTIBLE, 0, 0, \ - tty_unlock(tty); \ - schedule(); \ - tty_lock(tty)) #ifdef CONFIG_PROC_FS extern void proc_tty_register_driver(struct tty_driver *); -- cgit v1.2.3 From 2812d9e9fd94c54b0482215f579e6aa04452a322 Mon Sep 17 00:00:00 2001 From: Peter Hurley Date: Sat, 10 Oct 2015 20:28:42 -0400 Subject: tty: Combine SIGTTOU/SIGTTIN handling The job_control() check in n_tty_read() has nearly identical purpose and results as tty_check_change(). Both functions' purpose is to determine if the current task's pgrp is the foreground pgrp for the tty, and if not, to signal the current pgrp. Introduce __tty_check_change() which takes the signal to send and performs the shared operations for job control() and tty_check_change(). Signed-off-by: Peter Hurley 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 c2889f4331e1..533d7f6e2481 100644 --- a/include/linux/tty.h +++ b/include/linux/tty.h @@ -423,6 +423,7 @@ extern int tty_paranoia_check(struct tty_struct *tty, struct inode *inode, const char *routine); extern const char *tty_name(const struct tty_struct *tty); extern void tty_wait_until_sent(struct tty_struct *tty, long timeout); +extern int __tty_check_change(struct tty_struct *tty, int sig); extern int tty_check_change(struct tty_struct *tty); extern void __stop_tty(struct tty_struct *tty); extern void stop_tty(struct tty_struct *tty); -- cgit v1.2.3 From e176058f0de53c2346734e5254835e0045364001 Mon Sep 17 00:00:00 2001 From: Peter Hurley Date: Sat, 17 Oct 2015 16:36:23 -0400 Subject: tty: Abstract tty buffer work Introduce API functions to restart and cancel tty buffer work, rather than manipulate buffer work directly. Signed-off-by: Peter Hurley Signed-off-by: Greg Kroah-Hartman --- include/linux/tty.h | 2 ++ 1 file changed, 2 insertions(+) (limited to 'include/linux/tty.h') diff --git a/include/linux/tty.h b/include/linux/tty.h index 533d7f6e2481..5b04b0a5375b 100644 --- a/include/linux/tty.h +++ b/include/linux/tty.h @@ -467,6 +467,8 @@ extern void tty_buffer_free_all(struct tty_port *port); extern void tty_buffer_flush(struct tty_struct *tty, struct tty_ldisc *ld); extern void tty_buffer_init(struct tty_port *port); extern void tty_buffer_set_lock_subclass(struct tty_port *port); +extern bool tty_buffer_restart_work(struct tty_port *port); +extern bool tty_buffer_cancel_work(struct tty_port *port); 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, -- cgit v1.2.3