Re: cvs commit: src/lib/libthread_xu Makefile pthread.map src/li
Matthew Dillon wrote:
> :The management thread should be avoided, that introduces complex into
> :userland, I don't want to go old evil linuxthread way.
> :I only need one flag to indicate that the thread now executes in
> :kernel(pthread_exit() calls _exit()), so its userland resource is no
> :longer needed, e.g. its userland stack and user thread control block, so
> :other threads can reuse them when creating new thread or recycle it at
> :sometime later, but without this flag, there is always a race condition,
> :it is not safe to reuse it because that thread may be still using the
> :stack, although it called _exit(), but that does not say it is not using
> :the stack! calling _exit() pushes return address on stack, and it
> :destroys another thread's memory if the stack was reused by other
> :threads very quickly.
> :In detail, I want following feature:
> :a syscall allows userland to set an userland address, for example:
> :__sys_set_thread_exit_addr(int *addr), it remembers the addr
> :in kernel thread structure, if the thread calls _exit(),
> :in kernel, kernel code writes a value to addr, that's the only
> :thing I need to do userland garbage collection.
> :In this way I can avoid complex of management thread.
> :
> :Cheers,
> :David Xu
>
> Hmm. Well, I really dislike adding single-purpose system calls. If I
> do this we need to try to make the system call a bit more general-purpose.
> For example, we could use it to detect abnormal thread termination as
> well as deal with the stack resource race in the normal thread-exit case.
>
> So something like this:
>
> __sys_set_exit_data(int *addr, int data);
>
> Defined to be:
>
> "When a process exits the system will store the specified data into the
> specified address. Only one address may be registered per process.
> The feature can be disabled by passing addr = NULL.
>
> In an rfork/thread baesd system this may be used to detect abnormal
> process exits and to synchronize stack resource reuse with normal thread
> termination."
>
> How's that?
This is fine to me, did you consider how to exit whole process not
just a single thread ? right now, I am using _exit(), but it only
exits current thread, other threads can not be shutdown.
>
> -Matt
> Matthew Dillon
> <dillon@backplane.com>
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