On Wednesday 21 September 2005 21:49, Andrew Morton wrote: > "Paolo 'Blaisorblade' Giarrusso" <[EMAIL PROTECTED]> wrote: > > From: Paolo 'Blaisorblade' Giarrusso <[EMAIL PROTECTED]>
> The in_atomic() test in x86's do_page_fault() is in fact a message passed > into it from filemap.c's kmap_atomic(). Ok, this can be ok, but: > It has accidental side-effects, > such as making copy_to_user() fail if inside spinlocks when > CONFIG_PREEMPT=y. Sorry, but should it ever succeed inside spinlocks? I mean, should it ever call down() inside spinlocks? (We never do down_trylock, and ever if we did the x86 trick, that wouldn't make the whole thing safe at all - they still take the spinlock and potentially sleep. And it's legal only if no spinlock is held). Even if spinlocks don't always trigger in_atomic() - which means that we'd need to have a better fix for this. (Btw, I took the above reasoning from something said, as an aside, on LWN.net kernel page, about the FUTEX deadlock on mm->mmap_sem of ~ 2.6.8 - yes, it wasn't the full truth, but not totally dumb). > So I think this change is only needed if UML implements kmap_atomic, as in > arch/i386/mm/highmem.c, which it surely does not do? NACK, see above. -- 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 [email protected] https://lists.sourceforge.net/lists/listinfo/user-mode-linux-devel
