Messages in this thread | | | Date | Fri, 25 Apr 2008 17:50:00 +0200 | From | Ingo Molnar <> | Subject | Re: [PATCH 1/1] x86: fix text_poke |
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* Linus Torvalds <torvalds@linux-foundation.org> wrote:
> No. That whole code sequence is total and utter crap. It needs to be > rewritten. > > It first does a BUG_ON() if it's not naturally aligned (because that > wouldn't be atomic), and then it has code for page crossing! What a > TOTAL PIECE OF SH*T! > > Hint: > - if it's naturally aligned, it couldn't be page crossing ANYWAY > - and if it was a page-crosser, it sure as hell couldn't be atomic! > > The code is just crap, crap, crap. It needs to be rewritten from > scratch. I'll have a patch soonish.
yeah :(
it seems that this code only worked because text_poke_early() [which can take arbitrary length and alignment] does most of the patching, it is the real code-patching machinery that is used during early bootup - and that's not used later on.
text_poke() itself only applies/unapplies the LOCK prefix - a single byte. We shouldnt be doing that at all: the cost of LOCK is insignificant (a few cycles) and most systems are SMP anyway.
any other type of code patching should use stop_machine_run(), where every CPU is stopped with irqs disabled.
Ingo
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