Messages in this thread Patch in this message | | | Date | Fri, 16 Mar 2012 13:14:45 -0700 | From | "" <> | Subject | Re: [PATCH v2] tty: hold lock across tty buffer finding and buffer filling |
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Jiri,
Do you have any objections to me applying the patch below?
thanks,
greg k-h
On Fri, Mar 16, 2012 at 03:00:26AM +0000, Tu, Xiaobing wrote: > From: Xiaobing Tu <xiaobing.tu@intel.com> > > tty_buffer_request_room is well protected, but while after it returns, > it releases the port->lock. tty->buf.tail might be modified > by either irq handler or other threads. The patch adds more protection > by holding the lock across tty buffer finding and buffer filling. > Signed-off-by: Alek Du <alek.du@intel.com> > Signed-off-by: Xiaobing Tu <xiaobing.tu@intel.com> > --- > drivers/tty/tty_buffer.c | 85 +++++++++++++++++++++++++++++++++++----------- > 1 files changed, 65 insertions(+), 20 deletions(-) > > diff --git a/drivers/tty/tty_buffer.c b/drivers/tty/tty_buffer.c > index 6c9b7cd..91e326f 100644 > --- a/drivers/tty/tty_buffer.c > +++ b/drivers/tty/tty_buffer.c > @@ -185,25 +185,19 @@ static struct tty_buffer *tty_buffer_find(struct tty_struct *tty, size_t size) > /* Should possibly check if this fails for the largest buffer we > have queued and recycle that ? */ > } > - > /** > - * tty_buffer_request_room - grow tty buffer if needed > + * __tty_buffer_request_room - grow tty buffer if needed > * @tty: tty structure > * @size: size desired > * > * Make at least size bytes of linear space available for the tty > * buffer. If we fail return the size we managed to find. > - * > - * Locking: Takes tty->buf.lock > + * Locking: Caller must hold tty->buf.lock > */ > -int tty_buffer_request_room(struct tty_struct *tty, size_t size) > +static int __tty_buffer_request_room(struct tty_struct *tty, size_t size) > { > struct tty_buffer *b, *n; > int left; > - unsigned long flags; > - > - spin_lock_irqsave(&tty->buf.lock, flags); > - > /* OPTIMISATION: We could keep a per tty "zero" sized buffer to > remove this conditional if its worth it. This would be invisible > to the callers */ > @@ -225,9 +219,30 @@ int tty_buffer_request_room(struct tty_struct *tty, size_t size) > size = left; > } > > - spin_unlock_irqrestore(&tty->buf.lock, flags); > return size; > } > + > + > +/** > + * tty_buffer_request_room - grow tty buffer if needed > + * @tty: tty structure > + * @size: size desired > + * > + * Make at least size bytes of linear space available for the tty > + * buffer. If we fail return the size we managed to find. > + * > + * Locking: Takes tty->buf.lock > + */ > +int tty_buffer_request_room(struct tty_struct *tty, size_t size) > +{ > + unsigned long flags; > + int length; > + > + spin_lock_irqsave(&tty->buf.lock, flags); > + length = __tty_buffer_request_room(tty, size); > + spin_unlock_irqrestore(&tty->buf.lock, flags); > + return length; > +} > EXPORT_SYMBOL_GPL(tty_buffer_request_room); > > /** > @@ -249,14 +264,22 @@ int tty_insert_flip_string_fixed_flag(struct tty_struct *tty, > int copied = 0; > do { > int goal = min_t(size_t, size - copied, TTY_BUFFER_PAGE); > - int space = tty_buffer_request_room(tty, goal); > - struct tty_buffer *tb = tty->buf.tail; > + int space; > + unsigned long flags; > + struct tty_buffer *tb; > + > + spin_lock_irqsave(&tty->buf.lock, flags); > + space = __tty_buffer_request_room(tty, goal); > + tb = tty->buf.tail; > /* If there is no space then tb may be NULL */ > - if (unlikely(space == 0)) > + if (unlikely(space == 0)) { > + spin_unlock_irqrestore(&tty->buf.lock, flags); > break; > + } > memcpy(tb->char_buf_ptr + tb->used, chars, space); > memset(tb->flag_buf_ptr + tb->used, flag, space); > tb->used += space; > + spin_unlock_irqrestore(&tty->buf.lock, flags); > copied += space; > chars += space; > /* There is a small chance that we need to split the data over > @@ -286,14 +309,22 @@ int tty_insert_flip_string_flags(struct tty_struct *tty, > int copied = 0; > do { > int goal = min_t(size_t, size - copied, TTY_BUFFER_PAGE); > - int space = tty_buffer_request_room(tty, goal); > - struct tty_buffer *tb = tty->buf.tail; > + int space; > + unsigned long __flags; > + struct tty_buffer *tb; > + > + spin_lock_irqsave(&tty->buf.lock, __flags); > + space = __tty_buffer_request_room(tty, goal); > + tb = tty->buf.tail; > /* If there is no space then tb may be NULL */ > - if (unlikely(space == 0)) > + if (unlikely(space == 0)) { > + spin_unlock_irqrestore(&tty->buf.lock, __flags); > break; > + } > memcpy(tb->char_buf_ptr + tb->used, chars, space); > memcpy(tb->flag_buf_ptr + tb->used, flags, space); > tb->used += space; > + spin_unlock_irqrestore(&tty->buf.lock, __flags); > copied += space; > chars += space; > flags += space; > @@ -344,13 +375,20 @@ EXPORT_SYMBOL(tty_schedule_flip); > int tty_prepare_flip_string(struct tty_struct *tty, unsigned char **chars, > size_t size) > { > - int space = tty_buffer_request_room(tty, size); > + int space; > + unsigned long flags; > + struct tty_buffer *tb; > + > + spin_lock_irqsave(&tty->buf.lock, flags); > + space = __tty_buffer_request_room(tty, size); > + > + tb = tty->buf.tail; > if (likely(space)) { > - struct tty_buffer *tb = tty->buf.tail; > *chars = tb->char_buf_ptr + tb->used; > memset(tb->flag_buf_ptr + tb->used, TTY_NORMAL, space); > tb->used += space; > } > + spin_unlock_irqrestore(&tty->buf.lock, flags); > return space; > } > EXPORT_SYMBOL_GPL(tty_prepare_flip_string); > @@ -374,13 +412,20 @@ EXPORT_SYMBOL_GPL(tty_prepare_flip_string); > int tty_prepare_flip_string_flags(struct tty_struct *tty, > unsigned char **chars, char **flags, size_t size) > { > - int space = tty_buffer_request_room(tty, size); > + int space; > + unsigned long __flags; > + struct tty_buffer *tb; > + > + spin_lock_irqsave(&tty->buf.lock, __flags); > + space = __tty_buffer_request_room(tty, size); > + > + tb = tty->buf.tail; > if (likely(space)) { > - struct tty_buffer *tb = tty->buf.tail; > *chars = tb->char_buf_ptr + tb->used; > *flags = tb->flag_buf_ptr + tb->used; > tb->used += space; > } > + spin_unlock_irqrestore(&tty->buf.lock, __flags); > return space; > } > EXPORT_SYMBOL_GPL(tty_prepare_flip_string_flags); > -- > 1.7.4.1
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