scx_lavd: trace WINESYNC

[multics69]

scx_lavd now has a measure to mitigate the lock holder preemption problem (#779).
To know whether a task holds a lock or not, it traces lock APIs (e.g., mutex, semaphore, futex) in the kernel.
One missing part is WINESYNC, which is a kernel-level lock of Wine (windows emulator).
A starting point to support WINESYNC is as follows:

• https://lore.kernel.org/lkml/20240519202454.1192826-28-zfigura@codeweavers.com/
• https://github.com/torvalds/linux/blob/master/drivers/misc/ntsync.c
• https://www.youtube.com/watch?v=NjU4nyWyhU8

[ptr1337]

I think this is a pretty future task. The complete work/review of NTSync has been stalled since a while and it will take until this is going to be a thing for wine/proton.

Couldnt you do the same also for fsync?

[multics69]

I agree. I am also waiting for NTSync (W{INEsync) is merged.

In my understanding, fsync uses futex so the current futex tracing should cover fsync. Am I wrong?