> -----Original Message-----
> From: Chip Bilbrey [mailto:c...@bilbrey.org]
> Sent: Monday, November 6, 2017 12:33 AM
> To: Oleksandr Shamray <oleksan...@mellanox.com>
> Cc: gre...@linuxfoundation.org; a...@arndb.de; linux-
> ker...@vger.kernel.org; linux-arm-ker...@lists.infradead.org;
> devicet...@vger.kernel.org; open...@lists.ozlabs.org; j...@jms.id.au;
> j...@resnulli.us; tklau...@distanz.ch; linux-ser...@vger.kernel.org;
> m...@shout.net; Vadim Pasternak <vad...@mellanox.com>; system-sw-low-
> level <system-sw-low-le...@mellanox.com>; robh...@kernel.org; openocd-
> devel-ow...@lists.sourceforge.net; linux-...@vger.kernel.org;
> da...@davemloft.net; mche...@kernel.org; Jiri Pirko <j...@mellanox.com>
> Subject: Re: [v11,1/4] drivers: jtag: Add JTAG core driver
>
>
> Oleksandr Shamray writes:
[..]
> I notice the single-open()-per-device lock was dropped by request in an
> earlier
> revision of your patches, but multiple processes trying to drive a single JTAG
> master could wreak serious havoc if transactions get interleaved. Would
> something like an added JTAG_LOCKCHAIN/UNLOCKCHAIN
> ioctl() for exclusive client access be reasonable to prevent this?
>
Yes, it dropped by recommendation of Greg KH <gre...@linuxfoundation.org>.
Greg, what you can suggest about it. May be better to add again
single-open()-per-device lock with right locking way like:
>if (mutex_lock_interruptible(&jtag->open_lock)) {
> return -ERESTARTSYS;
>}
>
>if (jtag->opened) {
> mutex_unlock(&jtag->open_lock);
> return -EINVAL;
>}
>
>nonseekable_open(inode, file);
>file->private_data = jtag;
>jtag->opened++;
>mutex_unlock(&jtag->open_lock);
>
Thaks.
> -Chip
