(gdb) thread apply all bt
Thread 2 (Thread 0x7ffff730e700 (LWP 17729)):
#0  0x00007ffff7bcd910 in sem_wait () from /usr/lib/libpthread.so.0
#1  0x000000000044f95c in core.thread.suspend(core.thread.Thread) ()
#2  0x000000000044e188 in thread_suspendAll ()
#3  0x00000000004478ae in gc.gc.Gcx.fullcollect() ()
#4  0x0000000000444b82 in gc.gc.GC.mallocNoSync(ulong, uint, ref ulong, const(TypeInfo)) ()
#5  0x0000000000444a82 in gc.gc.GC.malloc(ulong, uint, ulong*, const(TypeInfo)) ()
#6  0x00000000004365f9 in gc_malloc ()
#7  0x000000000042f1a1 in _d_newclass ()
#8  0x000000000043c24e in core.runtime.defaultTraceHandler(void*) ()
#9  0x000000000043bcd1 in _d_traceContext ()
#10 0x0000000000436dd4 in _d_createTrace ()
#11 0x000000000042e8c6 in _d_throwc ()
#12 0x000000000042d13a in _d_assert ()
#13 0x000000000042ad51 in main.__assert(int) ()
#14 0x000000000042a698 in main.IFoo.foo().__require() ()
#15 0x000000000042a6be in main.Foo.foo() ()
#16 0x000000000042a804 in main.run() ()
#17 0x000000000043650c in core.thread.Thread.run() ()
#18 0x0000000000436275 in thread_entryPoint ()
#19 0x00007ffff7bc6314 in start_thread () from /usr/lib/libpthread.so.0
#20 0x00007ffff73f73ed in clone () from /usr/lib/libc.so.6

Thread 1 (Thread 0x7ffff7fca780 (LWP 17725)):
#0  0x00007ffff7bc74f5 in pthread_join () from /usr/lib/libpthread.so.0
#1  0x000000000042d99b in core.thread.Thread.join(bool) ()
#2  0x000000000042a7cc in D main ()