I've attached a program that reproduces the problem for me. The system this is running on is the following (Yes, I know it is old but I have very little control over the OS and compiler): Distribution: RHEL 4 $ uname -a Linux jwhp8400.houston.lgc.com 2.6.9-67.ELsmp #1 SMP Wed Nov 7 13:56:44 EST 2007 x86_64 x86_64 x86_64 GNU/Linux Compiler: g++ 3.4.6 boost: 1.39.0 boost.context: 0.2.0 boost.fiber: 0.5.1 boost.task: svn revision 67209 The code of interest is: void f1() { std::cout << "\t" << "f1" << std::endl; } void f2() { std::cout << "\t" << "f2" << std::endl; } void demo() { typedef boost::tasks::static_pool< boost::tasks::unbounded_fifo > pool_type; pool_type pool(boost::tasks::poolsize(4), boost::tasks::stacksize(1024 * 128)); std::cout << "Starting" << std::endl; boost::tasks::async(boost::tasks::make_task(f1), pool); boost::tasks::async(boost::tasks::make_task(f2), pool); pool.shutdown(); std::cout << "Done" << std::endl; } Whenever poolsize is greater than 1, I sometimes receive the following sigsegv: (gdb) where #0 0x0000002a95d7d8db in boost::fibers::detail::trampoline (vp=0xffffffff96400ac0) at libs/fiber/src/detail/info_base.cpp:25 #1 0x0000003c0203e960 in __correctly_grouped_prefixwc () from /lib64/tls/libc.so.6 #2 0x0000000000000000 in ?? () (gdb) print *self Cannot access memory at address 0xffffffff96400ac0 Am I missing a fundamental concept with the way that boost::tasks::static_pool works or is there something else going on? Thanks