Messages in this thread | | | From | "Du, Alek" <> | Subject | RE: [PATCH] tty: hold lock across tty buffer finding and buffer filling | Date | Fri, 16 Mar 2012 10:08:26 +0000 |
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If you really look at the original patch from Xiaobing, the tty_prepare_flip_string is also patched :-) Actually it fills up all the possible spin_lock gaps in tty_buffer.c
@@ -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; }
Thanks, Alek -----Original Message----- From: Jiri Slaby [mailto:jirislaby@gmail.com] On Behalf Of Jiri Slaby Sent: Friday, March 16, 2012 6:04 PM To: Du, Alek Cc: jiris >> Jiri Slaby; Alan Cox; Tu, Xiaobing; linux-kernel@vger.kernel.org; gregkh@linuxfoundation.org; Zhang, Yanmin; Zuo, Jiao Subject: Re: [PATCH] tty: hold lock across tty buffer finding and buffer filling
On 03/16/2012 11:01 AM, Du, Alek wrote: > We prepared the buffer, and use it. And during this, we don't release the spinlock of buf.lock, how the flush could happen? > > A > spin_lock > prepare the buffer > user the buffer > spin unlock > > > B > Spin_lock > Flush > Free the buffer > Put buf.tail = NULL > Spin unlock
Well, you do. Not all drivers use tty_insert_flip_string. Take a look at tty_prepare_flip_string and its users.
thanks, -- js suse labs
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