tree 6e6df4c447d16f68f748cd19bbd09511b0fb58b2
parent da7061614e7d11f0a0db96a5f507feca4ac9fa17
author Kautuk Consul <consul.kautuk@gmail.com> 1315970781 +0530
committer Greg Kroah-Hartman <gregkh@suse.de> 1321032914 -0800

staging: quatech_usb2: Potential lost wakeup scenario in TIOCMIWAIT

commit e8df1674d383d2ecc6efa8d7dba74c03aafdfdd7 upstream.

If the usermode app does an ioctl over this serial device  by
using TIOCMIWAIT, then the code will wait by setting the current
task state to TASK_INTERRUPTIBLE and then calling schedule().
This will be woken up by the qt2_process_modem_status on URB
completion when the port_extra->shadowMSR is set to the new
modem status.

However, this could result in a lost wakeup scenario due to a race
in the logic in the qt2_ioctl(TIOCMIWAIT) loop and the URB completion
for new modem status in qt2_process_modem_status.
Due to this, the usermode app's task will continue to sleep despite a
change in the modem status.

Signed-off-by: Kautuk Consul <consul.kautuk@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>