id	summary	reporter	owner	description	type	status	milestone	component	version	severity	resolution	keywords	cc
6377	Condition variable blocks when changing time	Johan Borkhuis <johan@…>	viboes	"I am using Linux on an ARM system, running Boost 1.47. My application needs accurate timing, and for this I use a POSIX timer using SIGRTMIN. This part is not something that I can control, it is an external library that implements this. I use condition variables as a timing mechanism within my software.

When I use condition variables without the POSIX timer there is no problem. The timing continues correctly, even if I change the time forward or backward.

When I start the POSIX timer the condition variable does not time-out when I change the time backward. It only times out when the original time (plus timeout) is reached.

When I changed the clock of the pthread condition variable to monotonic (call to pthread_condattr_setclock(&condattr, CLOCK_MONOTONIC)) the result was OK
again. 

Attached is a test application that shows the problem and implements a solution. This solution is not within the Boost library but directly as a POSIX condition variable.
Options to the test application:
{{{
-b: use boost condition variable
-s: generate POSIX signals
}}}

When running the testapplication with -bs the application will stop reporting when the time is changed backwards. When the time is set back to a time after the time the time was changed the application will continue."	Bugs	closed	Boost 1.60.0	thread	Boost 1.47.0	Problem	fixed	condition variable