Messages in this thread | | | Subject | Re: [PATCH] x86-64: espfix for 64-bit mode *PROTOTYPE* | From | "H. Peter Anvin" <> | Date | Mon, 21 Apr 2014 18:47:52 -0700 |
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Race condition (although with x86 being globally ordered, it probably can't actually happen.) The bitmask is probably the way to go.
On April 21, 2014 6:28:12 PM PDT, Andrew Lutomirski <amluto@gmail.com> wrote: >On Mon, Apr 21, 2014 at 6:14 PM, H. Peter Anvin <hpa@zytor.com> wrote: >> I wanted to avoid the "another cpu made this allocation, now I have >to free" crap, but I also didn't want to grab the lock if there was no >work needed. > >I guess you also want to avoid bouncing all these cachelines around on >boot on bit multicore machines. > >I'd advocate using the bitmap approach or simplifying the existing >code. For example: > >+ for (n = 0; n < ESPFIX_PUD_CLONES; n++) { >+ pud = ACCESS_ONCE(pud_p[n]); >+ if (!pud_present(pud)) >+ return false; >+ } > >I don't see why that needs to be a loop. How can one clone exist but >not the others? > >--Andy
-- Sent from my mobile phone. Please pardon brevity and lack of formatting.
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