Enable/Disable Futex support for io_uring

[mrVrAlex]

For now during build swoole from source code configure script check linux kernel version (>6.7) and enable futex support automatically. But what happen if build happened for example on kernel v6.8 (or just in docker container with latest kernel), but docker container will be run on host machine with kernel v6.6? io_uring will not works?
It will be common situation in real world, LTS linux release - v6.6 and another LTS v6.12 only recently appear - all cloud & hosters, etc do not have fresh linux kernel...
For now can possible not using io_uring (do not include --enable-iouring) but no --enable-futex or --disable-futex configure options...

[NathanFreeman]

The enabling or disabling of the iouring futex feature is determined by the output of uname -r. You need to execute uname -r in the Docker container to see if the output reflects the host's kernel information or the Docker image's kernel information.

[cjavad]

Alternatively using io_uring_opcode_supported will provide more accurate information with the probe feature of liburing. e.i. io_uring_opcode_supported(probe, IORING_OP_FUTEX_WAIT)

[mrVrAlex]

It is not a answer.
If I build swoole on linux kernel 6.8 with --enable-iouring for example on base alpine:3.21 docker image - then during build futex feature will be enabled.
BUT if I will run container with it docker image on host machine with OLD linux kernel like 6.1 - what exactly will happen with file IO operations?

[NathanFreeman]

For file operations, it doesn't have much impact; the main purpose of the iouring futex feature is to support coroutine locks.