value is passed as the `val` argument. The requests returns the old
concurrency level on success.
+
- A zero or negative value for `val` means 'automatic' and is recomputed
- as the current number of online CPUs as
- `sysconf(_SC_NPROCESSORS_ONLN)` would return.
+A zero or negative value for `val` means 'automatic' and is recomputed as the
+current number of online CPUs as `sysconf(_SC_NPROCESSORS_ONLN)` would return.
`PWQR_REGISTER`::
Registers the calling thread to be taken into account by the pool
address `addr` still contains the value `val` (in the fashion of `futex(2)`).
If it doesn't then the call doesn't block. Else the calling thread is blocked
until a `PWQR_WAKE` command is received.
++
+`addr` must of course be a pointer to an aligned integer which stores the
+reference ticket in userland.
`PWQR_PARK`::
Puts the thread in park mode. Those are spare threads to avoid