Re: [patch 4/4] mISDN: misc timerdev fixes

On Tue, 23 Sep 2008 14:00:30 +0200 Karsten Keil [off-list ref] wrote:

On Tue, Sep 23, 2008 at 07:45:34AM -0400, Christoph Hellwig wrote:

quoted

On Tue, Sep 23, 2008 at 04:30:05AM -0700, Andrew Morton wrote:

quoted

so.. this?

Much better.

quoted

--- a/drivers/isdn/mISDN/timerdev.c~misdn-misc-timerdev-fixes-fix
+++ a/drivers/isdn/mISDN/timerdev.c

@@ -61,7 +61,7 @@ mISDN_open(struct inode *ino, struct fil
 	init_waitqueue_head(&dev->wait);
 	filep->private_data = dev;
 	__module_get(THIS_MODULE);
-	return 0;
+	return nonseekable_open(ino, filep);

But this also shows that mISDN is kinda stuck in a different century.
Doing __module_get(THIS_MODULE) at the end of ->open is utterly racy,
it really needs to set a owner field in file_operations and rip this
cruft out.

Btw, can anyone explain WTF this timerdev module is doing?  It's not
using any functionality from the rest of mISDN, it's not exporting
any functionality to it either but just provides a really awkward way
to expose dumb timers to userspace.  What does it provide that the
normal timer syscalls can't provide?

This version only makes the programing of upper ISDN layers easier,
you only need to watch /dev/mISDNtimer together with the sockets in one
select call.

sys_timerfd_create() can do this?

The next version will have a option to synchronise the timer with
the ISDN hardware clock which would avoid additional jitter if you need to
bridge channels in software.

hrm.  If that's really really useful and actually works then I guess it
might then be justifiable.