id	summary	reporter	owner	description	type	status	milestone	component	version	severity	resolution	keywords	cc
7422	Provide a condition variable with zero-overhead performance penality	maxim.yegorushkin@…	viboes	"In boost versions prior to 1.45 condition_variable was a zero-overhead thin wrapper over pthread_cond_t.

In version 1.45 an internal mutex was added to condition_variable to improve thread cancellation support as described elsewhere (can't add the link to gmane archive because Trac thinks it's spam).

Since version 1.45 calling condition_variable::wait*() and condition_variable::notify*() lock the internal mutex. Doing so causes performance regressions for latency sensitive applications that don't use thread cancellation. To put it in other words, condition_variable was essentially turned into condition_variable_any.

Could the old version of condition_variable be added back please? 

A good idea seems to be requiring a macro, for example BOOST_THREADS_REQUIRE_THREAD_CANCELLATION, to be defined for condition_variable to include the internal mutex or be an alias for condition_variable_any. A call to thread::interrupt() would fail at compile time if BOOST_THREADS_REQUIRE_THREAD_CANCELLATION is not defined. Things may get more complicated if any compiled boost libraries use condition_variable though.
"	Feature Requests	closed	Boost 1.53.0	thread	Boost 1.51.0	Regression	fixed	condition_variable	vicente.botet@… viboes