> -----Original Message----- > From: Chip Bilbrey [mailto:[email protected]] > Sent: Monday, November 6, 2017 12:33 AM > To: Oleksandr Shamray <[email protected]> > Cc: [email protected]; [email protected]; linux- > [email protected]; [email protected]; > [email protected]; [email protected]; [email protected]; > [email protected]; [email protected]; [email protected]; > [email protected]; Vadim Pasternak <[email protected]>; system-sw-low- > level <[email protected]>; [email protected]; openocd- > [email protected]; [email protected]; > [email protected]; [email protected]; Jiri Pirko <[email protected]> > 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 <[email protected]>. 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
