libkse and SMP (was Re: USB bulk read & pthreads)

[Julian Elischer]

On Sat, 24 May 2003, Valentin Nechayev wrote:

>  Fri, May 23, 2003 at 16:33:07, eischen (Daniel Eischen) wrote about "Re: libkse and SMP (was Re: USB bulk read & pthreads)": 
> 
> DE> I'm not sure if what you meant here, but here's a (hopefully)
> DE> clearer explanation.
> 
> DE> All threads that are created with PTHREAD_SCOPE_PROCESS
> DE> (the default) will run in the same (initial) KSEG.  The
> DE> initial KSEG will have as many KSEs as CPUs by default.
> DE> When a scope process thread blocks in the kernel, upcalls
> DE> are made to the originating KSE and a new thread is scheduled.
> DE> When scope process threads unblock in the kernel, upcalls
> DE> are made to one or more of the same KSEs within the initial
> DE> KSEG to notify the library that the threads can be resumed.
> 
> DE> Each scope system thread gets its own KSE/KSEG pair in which
> DE> to run.
> 
> Sorry, I again lost understanding of this ;((
> Consider system with single CPU and 2 threads (with process scope) which
> both calls blocking disk read. Can the second thread block in read()
> before first thread returns from blocking read()? Or system scope
> is required for this?

no, PROCESS scope threads can block and control will return to the
userland thread scheduler to allow it to schedule another thread.
In other words, the two read()s are independent of each other.

> 
> 
> -netch-
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