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Re: [Xen-devel] libxl: spawning qemu while files are open

On Fri, 2013-10-18 at 15:26 +0000, Rob Hoes wrote:

> We could solve this by opening the suspend-image file in xenopsd using
> the O_CLOEXEC flag, causing the file to be closed when executing qemu.
> However, we are worried that this behaviour may still cause trouble in
> multi-threaded programs such as xenopsd, unless all files it ever
> opens are opened with O_CLOEXEC, which is easily forgotten.

I'm afraid this is exactly what you need to do.

libxl itself jumps through considerable hoops to ensure it does this
itself, it's extra hard in a library... (have a look= for CLOEXEC in
tools/libxl/*.h for some details)

xenopsd being the consuming app should have an easier time of it.

> Would it be possible for libxl to spawn qemu in such a way that it
> won't inherit open files?

I don't think POSIX has any functionality which allows for that to be
reliably implemented.


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