On 24.04.2020 05:22, Jason R Thorpe wrote:
> Module Name: src
> Committed By: thorpej
> Date: Fri Apr 24 03:22:06 UTC 2020
>
> Modified Files:
> src/sys/compat/linux/common: linux_exec.c linux_sched.c
> src/sys/kern: kern_exec.c kern_exit.c kern_fork.c kern_lwp.c
> kern_proc.c sys_lwp.c
> src/sys/sys: lwp.h proc.h
>
> Log Message:
> Overhaul the way LWP IDs are allocated. Instead of each LWP having it's
> own LWP ID space, LWP IDs came from the same number space as PIDs. The
> lead LWP of a process gets the PID as its LID. If a multi-LWP process's
> lead LWP exits, the PID persists for the process.
>
> In addition to providing system-wide unique thread IDs, this also lets us
> eliminate the per-process LWP radix tree, and some associated locks.
>
> Remove the separate "global thread ID" map added previously; it is no longer
> needed to provide this functionality.
>
> Nudged in this direction by ad@ and chs@.
>
This is a good idea (and preexisting in other kernels), unfortunately we
had locking issues in rust. If a multithreaded process is forked, we
shall create a replica of a calling thread and keep mutexes functional.
We tried to preserve the caller's LWP to guarantee this.
This problem can be back. I don't ask to revert or revisit this change,
but if it will be back, we shall find a solution for it.
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