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0 pointsdevit5y ago0 comments

You can use the kcmp system call with KCMP_FILE argument to find out if two fds point to the same files structure (of course you must use this as the custom comparison function of a sort algorithm so you don't end up with quadratic run time).

Linux has a project called CRIU that can save and restore processes to disk without needing additional kernel modules, so pretty much all state is already gettable and settable from user space.

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ksml5y ago· 3 in thread

I can't do that across processes, though, can I? (to see whether two processes have file descriptors pointing to the same open file) edit -- it does look like it works cross-process!

I hadn't heard of CRIU. I'll check that out. (edit: CRIU looks super useful. I think the speed/overhead of snapshotting will decide whether I can use it for this project, but I can imagine it being handy in the future regardless. Thanks for the link.)

dilyevsky5y ago

I recommend checking out podman (or docker) - they have built-in criu support. Otherwise you’ll need some other namespacing mechanism to avoid colliding pids

ksml5y ago

Every C Playground program runs in a Docker container, so this is already perfectly set up for CRIU. I might give it a try!

dilyevsky5y ago

Also check out kcmp man it totally allows you to compare fds across pids

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