On Tuesday 08 November 2005 16:43, Jeff Dike wrote: > On Mon, Nov 07, 2005 at 09:13:19PM -0800, Can Sar wrote: > > Do the other threads (particularly the user thread) ever > > do something else that would be important? > > The user thread doesn't. The IO thread does, if you wish to do IO.
Since he needs to be _really_ single-threaded (and he may very possibly be trying to run something like Valgrind on UML) he may even run UBD without the I/O thread. The code still exists, even if some bugs may have crept in since 2.6.9 (guess not, there has been no major rework). Basically, if io_thread_pid == -1, the code instead to to asynchronous I/O via this separate thread, does directly I/O by itself. For normal usage, it's a bad idea - UML won't be able to schedule another thread until completion of that I/O request (much like green-threads do when implemented the simple way). Btw, usage of sigjmp()/longjmp() (between kernel threads) is actually green-threads said another way (like Jeff said below). Btw, even userspace programs have a "stub" in the kernelspace thread. In that case, through, it's just userspace(): an infinite loop running ptrace to intercept and nullify syscalls and segfaults, basically. > And you can easily dispense with the sigio emulation thread. > > Furthermore is the actual kernel process multi threaded? > > It does what amounts to user-level threads - i.e. there are multiple > execution contexts in it, implemented with setjmp/longjmp, but that's > not visible from the outside. -- Inform me of my mistakes, so I can keep imitating Homer Simpson's "Doh!". Paolo Giarrusso, aka Blaisorblade (Skype ID "PaoloGiarrusso", ICQ 215621894) http://www.user-mode-linux.org/~blaisorblade ___________________________________ Yahoo! Mail: gratis 1GB per i messaggi e allegati da 10MB http://mail.yahoo.it ------------------------------------------------------- SF.Net email is sponsored by: Tame your development challenges with Apache's Geronimo App Server. Download it for free - -and be entered to win a 42" plasma tv or your very own Sony(tm)PSP. Click here to play: http://sourceforge.net/geronimo.php _______________________________________________ User-mode-linux-devel mailing list User-mode-linux-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/user-mode-linux-devel
