Bug 114033

Version:           0.12.4a (using KDE KDE 3.4.2)
Installed from:    Debian testing/unstable Packages
OS:                Linux

Nikita V. Youshchenko <yoush at cs.msu.su> reported the following problem on the Debian bug tracking system (http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=274998):

We are running a network where users work on X terminals connected to a
Debian Linux server.

Server has 2 writer devices; Linux seems to support simultaneous writing
on both.

While k3b started from one user was writing, k3b started from another user 
hanged at 'Scanning for devices' stage for a long time (several minutes). 
Although it unblocked before writing was complete, several minutes of 
freeze does not seem to be dummy-user-friendly :).

Most likely, this is caused by the fact that k3b uses some device ioclt 
while scanning, which in-kernel implementation tries to gain an exclusive 
lock to the device. Which in turn blocks entire process until another 
in-kernel usage unblocks the device.

Proper fix will probably need some cooperation between k3b and kernel 
people, to make it possible to read device characteristics (or whatever 
k3b needs while "scanning devices") without blocking.

To make situation a bit better involving k3b only, k3b probably should 
split scanning ioctls into a separate thread (to avoid GUI freeze) and 
inform user what's going on (e.g. "looks like device is locked by another 
user, waiting for lock to be released"). This will not solve the problem - 
user will still be unable to start writing on other writer - but anyway 
it's better than hanging.