Re: [RFC 7/9] ppp: use big tty mutex

From: Arnd Bergmann
Date: Wed Mar 31 2010 - 03:39:36 EST


On Wednesday 31 March 2010 06:37:12 AmÃrico Wang wrote:
> > @@ -362,7 +362,8 @@ static const int npindex_to_ethertype[NUM_NP] = {
> > */
> > static int ppp_open(struct inode *inode, struct file *file)
> > {
> > - cycle_kernel_lock();
> > + tty_lock();
> > + tty_unlock();
>
> I don't really get your point here. :) Why do you do this?

This is a blind conversion of the API from the common BKL functions to
the TTY lock functions. There is no cycle_tty_lock(), so I'm manually
doing the cycle.

The reason why cycle_kernel_lock() was introduced in the first place
is that some drivers may depend on the open() function not returning
while another CPU holds the BKL. I did not feel qualified (or motivated)
to determine if the ppp code has the behavior, so I left it at this.

Arnd
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