Messages in this thread | | | Date | Tue, 14 Nov 2017 12:10:46 +0100 | From | "" <> | Subject | Re: [v11,1/4] drivers: jtag: Add JTAG core driver |
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On Tue, Nov 14, 2017 at 10:34:49AM +0000, Oleksandr Shamray wrote: > > -----Original Message----- > > From: Chip Bilbrey [mailto:chip@bilbrey.org] > > Sent: Monday, November 6, 2017 12:33 AM > > To: Oleksandr Shamray <oleksandrs@mellanox.com> > > Cc: gregkh@linuxfoundation.org; arnd@arndb.de; linux- > > kernel@vger.kernel.org; linux-arm-kernel@lists.infradead.org; > > devicetree@vger.kernel.org; openbmc@lists.ozlabs.org; joel@jms.id.au; > > jiri@resnulli.us; tklauser@distanz.ch; linux-serial@vger.kernel.org; > > mec@shout.net; Vadim Pasternak <vadimp@mellanox.com>; system-sw-low- > > level <system-sw-low-level@mellanox.com>; robh+dt@kernel.org; openocd- > > devel-owner@lists.sourceforge.net; linux-api@vger.kernel.org; > > davem@davemloft.net; mchehab@kernel.org; Jiri Pirko <jiri@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 <gregkh@linuxfoundation.org>.
I asked to drop it as you didn't even implement it to work correctly :)
> 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)) {
You would stall an open? Why not just return saying you can't do that?
Anyway, if you want to only have one access to the device at a time, great, but do it in a way that works properly.
thanks,
greg k-h
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