Re: Serial-Core: USB-Serial port current issues.

[Russell King <rmk+lkml@arm.linux.org.uk>]

On Tue, Jun 13, 2006 at 07:28:29PM -0300, Luiz Fernando N. Capitulino wrote:
>  I took a look in the Serial Core code and didn't see why set_termios()
> and break_ctl() (plus tx_empty()) are not allowed to sleep: they doesn't
> seem to run in atomic context. So, are they allowed to sleep? Isn't the
> documentation out of date? I've even submitted a patch to fix it [2].

You are correct - and I will eventually apply your patch.  At the
moment, I'm throttling back on applying patches so that 2.6.17 can
finally appear (I don't want to be responsible for Linus saying
again "too many changes for -final, let's do another -rc".)

>  For get_mctrl() and set_mctrl() it seems possible to switch from a
> spinlock to a mutex, as they are not called from an interrupt context.
> Is this really possible? Would you agree with this change?

I don't know - that depends whether the throttle/unthrottle driver
methods are ever called from interrupt context or not.

What we could do is put a WARN_ON() or might_sleep() in there and
find out over time if they are called from non-process context.

-- 
Russell King
 Linux kernel    2.6 ARM Linux   - http://www.arm.linux.org.uk/
 maintainer of:  2.6 Serial core