Re: [PATCH v3 0/6] net/tap: Fix QEMU frozen issue when the maximum number of file descriptors is very large

[Michael Tokarev]

17.06.2023 08:36, Bin Meng wrote:
> Current codes using a brute-force traversal of all file descriptors
> do not scale on a system where the maximum number of file descriptors
> is set to a very large value (e.g.: in a Docker container of Manjaro
> distribution it is set to 1073741816). QEMU just looks frozen during
> start-up.

What's the reason to close all these file descriptors in the first place?

No other software I know does this.

For some situations, such closing is actually bad, -- think, eg,

  flock lockfile qemu-system-foo ...  --

this one opens a file, locks it using fcntl/flock, and executes the
command, keeping the file descriptor open across exec, so the file
stays locked until the process terminates. This works and works well.
Qemu with its let's-close-everything approach breaks this.

Why? :)

/mjt