About :: TODO :: Blog :: RSS :: Old blog :: Projects :: GIT :: Gallery :: Notes

Wed, 17 Jan 2007

pthread_create() vs. clone().


Did you ever tried to use clone() directly? I bet you never tried it at least with recent kernels.
First, exported clone() does not correspond to what kernel expects, it looks like it is only provided for compatibility. Manpage for that call is utterly obsoleted and incorrect (except useful flag description it contains _wrong_ descrition of parameters at least for i386).
But I do not search for easy ways - I have glibc sources and can dig into them.
That was my first impression of the man, who in theory can climb the Everest, fly to the space and understand math behind string theory (the latter only if time permits, it looks like the whole life can be spent there digging into more and more new subtheories).
Now I think that all three tasks described above can be much-much-much more solvable than digging in the glibc sources. And those people says that I poorly described kevent - hey, look into glibc NPTL implementation (and I even do not talk about its coding style) and pray you will never see this again, or just try to start a new thread using clone().

After about an hour of reverse engineering process trying to make __clone() work (note, that clone() does not work at all, just forget about this call, only __clone() is correct for i386 and 2.6 kernel), I managed to start new thread. It was a win, except very small problem, that it crashed somewhere in the provided function calling chain.
I want you to know, that I do not know low-level i386 arch enough to easily read and understand asm code (some years ago I managed to write asm application which entered protected mode in DOS, but I do not recall asm already, and actually never understood gas semantic good enough) found in sysdeps/unix/sysv/linux/i386/clone.S, so I miserably failed to proceed.

Yes, I started to use pthread_create() for SMP scalability. I do not hear how you scream 'loser', since you would be there too, but those of you, who still lurks here and ironically nod your head would better point me to something useful for understanding of how modern i386 (or actually any other arch) starts and works with threads/processes.

/devel/threading :: Link / Comments ()