Hello, L4 hackers! I have a question about Fiasco.OC. I am a bit stuck in understanding of how objects created by factory are destroyed? For example, we have a call from user space l4_factory_create_thread(). It creates object in Fiasco (file fiasco/src/kernel/factory.cpp) and map it using call map() from fiasco/src/kernel/map_util.cpp. However, the procedure of destruction of created objects (tasks, threads, gates, irqs, vms) is not clear: it seems that there is some kind of the "garbage collector", but I can not figure out some important things. Particularly: 1) where is the code which essentially destroys created objects (call destructors)? 2) what conditions make "garbage collection" to start? 3) how "garbage collection" can be forced from user-space?
As a use-case, I can propose the fork-bomb test from Genode framework: it creates lots of new Genode threads (thus, it makes a lot of new thread/gate/irq objects in Fiasco.OC). Thanks in advance for your answer.
Hi,
On Wed Mar 27, 2013 at 15:38:56 +0400, Sergey Grekhov wrote:
Hello, L4 hackers! I have a question about Fiasco.OC. I am a bit stuck in understanding of how objects created by factory are destroyed? For example, we have a call from user space l4_factory_create_thread(). It creates object in Fiasco (file fiasco/src/kernel/factory.cpp) and map it using call map() from fiasco/src/kernel/map_util.cpp. However, the procedure of destruction of created objects (tasks, threads, gates, irqs, vms) is not clear: it seems that there is some kind of the "garbage collector", but I can not figure out some important things. Particularly:
- where is the code which essentially destroys created objects (call destructors)?
- what conditions make "garbage collection" to start?
- how "garbage collection" can be forced from user-space?
Objects will be destroyed when their last mapping disappears in any task, aka when they're unmapped. See for a 'delete' operation in map_util.cpp for where they're destroyed.
Adam
l4-hackers@os.inf.tu-dresden.de