From 591cee0a35632031cd925392a1bce507dcfe9ea8 Mon Sep 17 00:00:00 2001 From: Arnd Bergmann Date: Thu, 2 Jan 2014 13:07:38 +0100 Subject: [PATCH] tty/amiserial: avoid interruptible_sleep_on interruptible_sleep_on is generally problematic and we want to get rid of it. In case of TIOCMIWAIT, that race is actually in user space and does not get fixed since we can only detect changes after entering the ioctl handler, but it removes one more caller. This instance can not be trivially replaced with wait_event, so I chose to open-code the wait loop using prepare_to_wait/finish_wait. Signed-off-by: Arnd Bergmann Cc: Geert Uytterhoeven Cc: Greg Kroah-Hartman Signed-off-by: Greg Kroah-Hartman --- drivers/tty/amiserial.c | 26 ++++++++++++++++++-------- 1 file changed, 18 insertions(+), 8 deletions(-) diff --git a/drivers/tty/amiserial.c b/drivers/tty/amiserial.c index 71630a2af42c..979e7c3ea2cb 100644 --- a/drivers/tty/amiserial.c +++ b/drivers/tty/amiserial.c @@ -1248,6 +1248,8 @@ static int rs_ioctl(struct tty_struct *tty, struct async_icount cprev, cnow; /* kernel counter temps */ void __user *argp = (void __user *)arg; unsigned long flags; + DEFINE_WAIT(wait); + int ret; if (serial_paranoia_check(info, tty->name, "rs_ioctl")) return -ENODEV; @@ -1288,25 +1290,33 @@ static int rs_ioctl(struct tty_struct *tty, cprev = info->icount; local_irq_restore(flags); while (1) { - interruptible_sleep_on(&info->tport.delta_msr_wait); - /* see if a signal did it */ - if (signal_pending(current)) - return -ERESTARTSYS; + prepare_to_wait(&info->tport.delta_msr_wait, + &wait, TASK_INTERRUPTIBLE); local_irq_save(flags); cnow = info->icount; /* atomic copy */ local_irq_restore(flags); if (cnow.rng == cprev.rng && cnow.dsr == cprev.dsr && - cnow.dcd == cprev.dcd && cnow.cts == cprev.cts) - return -EIO; /* no change => error */ + cnow.dcd == cprev.dcd && cnow.cts == cprev.cts) { + ret = -EIO; /* no change => error */ + break; + } if ( ((arg & TIOCM_RNG) && (cnow.rng != cprev.rng)) || ((arg & TIOCM_DSR) && (cnow.dsr != cprev.dsr)) || ((arg & TIOCM_CD) && (cnow.dcd != cprev.dcd)) || ((arg & TIOCM_CTS) && (cnow.cts != cprev.cts)) ) { - return 0; + ret = 0; + break; + } + schedule(); + /* see if a signal did it */ + if (signal_pending(current)) { + ret = -ERESTARTSYS; + break; } cprev = cnow; } - /* NOTREACHED */ + finish_wait(&info->tport.delta_msr_wait, &wait); + return ret; case TIOCSERGWILD: case TIOCSERSWILD: -- 2.34.1