On Tue, Nov 14, 2017 at 10:34:49AM +0000, Oleksandr Shamray wrote: > > -----Original Message----- > > From: Chip Bilbrey [mailto:chip@xxxxxxxxxxx] > > Sent: Monday, November 6, 2017 12:33 AM > > To: Oleksandr Shamray <oleksandrs@xxxxxxxxxxxx> > > Cc: gregkh@xxxxxxxxxxxxxxxxxxx; arnd@xxxxxxxx; linux- > > kernel@xxxxxxxxxxxxxxx; linux-arm-kernel@xxxxxxxxxxxxxxxxxxx; > > devicetree@xxxxxxxxxxxxxxx; openbmc@xxxxxxxxxxxxxxxx; joel@xxxxxxxxx; > > jiri@xxxxxxxxxxx; tklauser@xxxxxxxxxx; linux-serial@xxxxxxxxxxxxxxx; > > mec@xxxxxxxxx; Vadim Pasternak <vadimp@xxxxxxxxxxxx>; system-sw-low- > > level <system-sw-low-level@xxxxxxxxxxxx>; robh+dt@xxxxxxxxxx; openocd- > > devel-owner@xxxxxxxxxxxxxxxxxxxxx; linux-api@xxxxxxxxxxxxxxx; > > davem@xxxxxxxxxxxxx; mchehab@xxxxxxxxxx; Jiri Pirko <jiri@xxxxxxxxxxxx> > > 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@xxxxxxxxxxxxxxxxxxx>. 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 -- To unsubscribe from this list: send the line "unsubscribe linux-serial" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
