Messages in this thread Patch in this message | | | Date | Sun, 7 Nov 2004 23:10:15 +0300 | From | Sergey Vlasov <> | Subject | [PATCH] Update termios to use per tty semaphore (backport from 2.6.x) |
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This is a 2.4.x backport of the termios locking changes made in 2.6.x:
# 2004/10/02 15:46:35-07:00 alan@lxorguk.ukuu.org.uk # [PATCH] Update termios to use per tty semaphore # # This makes the agreed change of termios locking to be semaphore based # sleep locking. This is needed for USB in particular as it has to use # messaging to issue terminal mode changes. # # This code passes Torvalds test grades 0, 1 and 2 (it looks ok, it # compiles and it booted). It does mean that a driver cannot take an # atomic peek at termios data during an interrupt. Nobody seems to be # doing this although some of the driver receive paths for line # disciplines will eventually want to (n_tty currently doesn't do this # locked on the receive path). Since the ldisc is given a chance to copy # any essential bits on the ->set_termios path this seems not to be a # problem.
--- kernel-source-2.4.27/include/linux/tty.h.termios 2004-10-31 18:07:10 +0300 +++ kernel-source-2.4.27/include/linux/tty.h 2004-10-31 20:23:38 +0300 @@ -261,6 +261,7 @@ struct tty_struct { int magic; struct tty_driver driver; struct tty_ldisc ldisc; + struct semaphore termios_sem; struct termios *termios, *termios_locked; int pgrp; int session; --- kernel-source-2.4.27/drivers/char/tty_io.c.termios 2004-10-31 18:04:37 +0300 +++ kernel-source-2.4.27/drivers/char/tty_io.c 2004-10-31 20:26:13 +0300 @@ -118,8 +118,6 @@ extern void disable_early_printk(void); #define TTY_PARANOIA_CHECK 1 #define CHECK_TTY_COUNT 1 -/* Lock for tty_termios changes - private to tty_io/tty_ioctl */ -spinlock_t tty_termios_lock = SPIN_LOCK_UNLOCKED; struct termios tty_std_termios; /* for the benefit of tty drivers */ struct tty_driver *tty_drivers; /* linked list of tty drivers */ @@ -269,10 +267,9 @@ static int check_tty_count(struct tty_st static void tty_set_termios_ldisc(struct tty_struct *tty, int num) { - unsigned long flags; - spin_lock_irqsave(&tty_termios_lock, flags); + down(&tty->termios_sem); tty->termios->c_line = num; - spin_unlock_irqrestore(&tty_termios_lock, flags); + up(&tty->termios_sem); } /* @@ -803,10 +800,9 @@ void do_tty_hangup(void *data) if (tty->driver.flags & TTY_DRIVER_RESET_TERMIOS) { - unsigned long flags; - spin_lock_irqsave(&tty_termios_lock, flags); + down(&tty->termios_sem); *tty->termios = tty->driver.init_termios; - spin_unlock_irqrestore(&tty_termios_lock, flags); + up(&tty->termios_sem); } /* Defer ldisc switch */ @@ -2452,6 +2448,7 @@ static void initialize_tty_struct(struct tty->flip.tqueue.routine = flush_to_ldisc; tty->flip.tqueue.data = tty; init_MUTEX(&tty->flip.pty_sem); + init_MUTEX(&tty->termios_sem); init_waitqueue_head(&tty->write_wait); init_waitqueue_head(&tty->read_wait); tty->tq_hangup.routine = do_tty_hangup; --- kernel-source-2.4.27/drivers/char/tty_ioctl.c.termios 2004-10-31 18:04:37 +0300 +++ kernel-source-2.4.27/drivers/char/tty_ioctl.c 2004-10-31 20:31:47 +0300 @@ -29,8 +29,6 @@ #undef DEBUG -extern spinlock_t tty_termios_lock; - /* * Internal flag options for termios setting behavior */ @@ -99,7 +97,6 @@ static void change_termios(struct tty_st int canon_change; struct termios old_termios = *tty->termios; struct tty_ldisc *ld; - unsigned long flags; /* * Perform the actual termios internal changes under lock. @@ -107,7 +104,7 @@ static void change_termios(struct tty_st /* FIXME: we need to decide on some locking/ordering semantics for the set_termios notification eventually */ - spin_lock_irqsave(&tty_termios_lock, flags); + down(&tty->termios_sem); *tty->termios = *new_termios; unset_locked_termios(tty->termios, &old_termios, tty->termios_locked); @@ -147,8 +144,7 @@ static void change_termios(struct tty_st (ld->set_termios)(tty, &old_termios); tty_ldisc_deref(ld); } - spin_unlock_irqrestore(&tty_termios_lock, flags); - + up(&tty->termios_sem); } static int set_termios(struct tty_struct * tty, unsigned long arg, int opt) @@ -244,13 +240,13 @@ static int get_sgttyb(struct tty_struct struct sgttyb tmp; unsigned long flags; - spin_lock_irqsave(&tty_termios_lock, flags); + down(&tty->termios_sem); tmp.sg_ispeed = 0; tmp.sg_ospeed = 0; tmp.sg_erase = tty->termios->c_cc[VERASE]; tmp.sg_kill = tty->termios->c_cc[VKILL]; tmp.sg_flags = get_sgflags(tty); - spin_unlock_irqrestore(&tty_termios_lock, flags); + up(&tty->termios_sem); return copy_to_user(sgttyb, &tmp, sizeof(tmp)) ? -EFAULT : 0; } @@ -286,19 +282,18 @@ static int set_sgttyb(struct tty_struct int retval; struct sgttyb tmp; struct termios termios; - unsigned long flags; retval = tty_check_change(tty); if (retval) return retval; if (copy_from_user(&tmp, sgttyb, sizeof(tmp))) return -EFAULT; - spin_lock_irqsave(&tty_termios_lock, flags); + down(&tty->termios_sem); termios = *tty->termios; termios.c_cc[VERASE] = tmp.sg_erase; termios.c_cc[VKILL] = tmp.sg_kill; set_sgflags(&termios, tmp.sg_flags); - spin_unlock_irqrestore(&tty_termios_lock, flags); + up(&tty->termios_sem); change_termios(tty, &termios); return 0; } @@ -533,11 +528,11 @@ int n_tty_ioctl(struct tty_struct * tty, case TIOCSSOFTCAR: if (get_user(arg, (unsigned int *) arg)) return -EFAULT; - spin_lock_irqsave(&tty_termios_lock, flags); + down(&tty->termios_sem); tty->termios->c_cflag = ((tty->termios->c_cflag & ~CLOCAL) | (arg ? CLOCAL : 0)); - spin_unlock_irqrestore(&tty_termios_lock, flags); + up(&tty->termios_sem); return 0; default: return -ENOIOCTLCMD; --- kernel-source-2.4.27/Documentation/tty.txt.termios 2004-10-31 18:04:36 +0300 +++ kernel-source-2.4.27/Documentation/tty.txt 2004-10-31 20:23:38 +0300 @@ -158,8 +158,8 @@ write_room() - Return the number of char ioctl() - Called when an ioctl may be for the driver -set_termios() - Called on termios change, may get parallel calls, - may block for now (may change that) +set_termios() - Called on termios change, serialized against + itself by a semaphore. May sleep. set_ldisc() - Notifier for discipline change. At the point this is done the discipline is not yet usable. Can now[unhandled content-type:application/pgp-signature] | |