Messages in this thread | | | Date | Tue, 8 Feb 2011 00:20:45 +0100 | From | Andrea Arcangeli <> | Subject | Re: [PATCH] x86: hold mm->page_table_lock while doing vmalloc_sync |
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On Fri, Feb 04, 2011 at 01:27:33PM -0800, Jeremy Fitzhardinge wrote: > No, I don't think there's any xen-specific code which calls mmdrop (at > all, let alone in interrupt context). Erm, but I'm not sure where it > does. I had a thinko that "schedule" would be one of those places, but > calling that from interrupt context would cause much bigger problems :/ > > static void pgd_dtor(pgd_t *pgd)
I checked again and I don't see exactly where mmdrop or __mmdrop are called from irq context.
> No. I don't think I wrote that comment. It possibly just some ancient > lore that could have been correct at one point, or perhaps it never true.
I agree with that. But it'd be nice of more people could look into that so we at least can remove the misleading comment.
Where else can the pgd_lock be taken from irq context? Can we fix the deadlock with NR_CPUS < 4 with my patch? (with the ,flags removed from below?)
> > >>> @@ -247,7 +248,7 @@ void vmalloc_sync_all(void) > >>> if (!ret) > >>> break; > >>> } > >>> - spin_unlock_irqrestore(&pgd_lock, flags); > >>> + spin_unlock(&pgd_lock, flags); > >> Urp. Did this compile? > > Yes it builds > > (spin_unlock() shouldn't take a "flags" arg.) > > > > I'm not reposting a version that builds for 32bit x86 too until we > > figure out the mmdrop thing... > > Stick it in next and look for explosion reports?
I intended to correct that of course, I just meant it is no problem for 64bit builds and that's why I didn't notice the build failure before posting the patch. Clearly 32bit build would have failed ;).
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