lkml.org 
[lkml]   [2012]   [May]   [31]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [PATCH] tty: add lockdep annotations
    On Thu, 31 May 2012, Eric Dumazet wrote:

    > From: Eric Dumazet <edumazet@google.com>
    >
    > tty_lock_pair() do the right thing to avoid deadlocks, but should
    > instruct LOCKDEP of this to avoid a splat.

    I have submitted very similar patch to Greg/Alan already 3 days ago[1],
    but have been told that this is already fixed. Apparently it wasn't?

    [1] https://lkml.org/lkml/2012/5/28/226

    >
    > Signed-off-by: Eric Dumazet <edumazet@google.com>
    > ---
    > Latest Linus tree still hang on my machine, at least this patch removes
    > the lockdep problem...
    >
    > drivers/tty/tty_mutex.c | 19 +++++++++++++++----
    > 1 file changed, 15 insertions(+), 4 deletions(-)
    >
    > diff --git a/drivers/tty/tty_mutex.c b/drivers/tty/tty_mutex.c
    > index 69adc80..67feac9 100644
    > --- a/drivers/tty/tty_mutex.c
    > +++ b/drivers/tty/tty_mutex.c
    > @@ -6,11 +6,17 @@
    >
    > /* Legacy tty mutex glue */
    >
    > +enum {
    > + TTY_MUTEX_NORMAL,
    > + TTY_MUTEX_NESTED,
    > +};
    > +
    > /*
    > * Getting the big tty mutex.
    > */
    >
    > -void __lockfunc tty_lock(struct tty_struct *tty)
    > +static void __lockfunc tty_lock_nested(struct tty_struct *tty,
    > + unsigned int subclass)
    > {
    > if (tty->magic != TTY_MAGIC) {
    > printk(KERN_ERR "L Bad %p\n", tty);
    > @@ -18,7 +24,12 @@ void __lockfunc tty_lock(struct tty_struct *tty)
    > return;
    > }
    > tty_kref_get(tty);
    > - mutex_lock(&tty->legacy_mutex);
    > + mutex_lock_nested(&tty->legacy_mutex, subclass);
    > +}
    > +
    > +void __lockfunc tty_lock(struct tty_struct *tty)
    > +{
    > + return tty_lock_nested(tty, TTY_MUTEX_NORMAL);
    > }
    > EXPORT_SYMBOL(tty_lock);
    >
    > @@ -43,11 +54,11 @@ void __lockfunc tty_lock_pair(struct tty_struct *tty,
    > {
    > if (tty < tty2) {
    > tty_lock(tty);
    > - tty_lock(tty2);
    > + tty_lock_nested(tty2, TTY_MUTEX_NESTED);
    > } else {
    > if (tty2 && tty2 != tty)
    > tty_lock(tty2);
    > - tty_lock(tty);
    > + tty_lock_nested(tty, TTY_MUTEX_NESTED);
    > }
    > }
    > EXPORT_SYMBOL(tty_lock_pair);
    >
    >
    > --
    > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
    > the body of a message to majordomo@vger.kernel.org
    > More majordomo info at http://vger.kernel.org/majordomo-info.html
    > Please read the FAQ at http://www.tux.org/lkml/
    >

    --
    Jiri Kosina
    SUSE Labs



    \
     
     \ /
      Last update: 2012-05-31 14:21    [W:0.054 / U:179.036 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site