Messages in this thread | | | Date | Wed, 10 Dec 2014 13:13:25 +0100 | From | Richard Weinberger <> | Subject | Re: [BUG] uml panics with "Segfault with no mm" in v3.19-rc |
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Am 10.12.2014 um 12:59 schrieb Geert Uytterhoeven: > On Wed, Dec 10, 2014 at 11:49 AM, Richard Weinberger <richard@nod.at> wrote: >> Am 10.12.2014 um 11:46 schrieb Miklos Szeredi: >>> The guilty commit is: >>> >>> 00f634bc522d "asm-generic: add generic futex for !CONFIG_SMP" >> >> Thanks a lot Miklos! >> Your bisecting faster than I do. >> >> Let's dig into the issue! > > Do you need "select HAVE_FUTEX_CMPXCHG if FUTEX"?
> Cfr. commit e571c58f313d35c5 ("m68k: Skip futex_atomic_cmpxchg_inatomic() > test") and commit 03b8c7b623c80af2 ("futex: Allow architectures to skip > futex_atomic_cmpxchg_inatomic() test").
Bingo!
If UML selects HAVE_FUTEX_CMPXCHG the code path I've described in my previous mail is no longer taken and makes it work again. I did only a small test but nothing exploded so far.
> BTW, I still think the real problem is the wrong address space, cfr. > "[PATCH/RFC] futex: Switch to USER_DS for futex test" > (http://www.spinics.net/lists/linux-m68k/msg06597.html), so you may also > want to try that. > However, that caused problems on s390, as it ran too early: > http://permalink.gmane.org/gmane.linux.kernel.next/30165
Yeah, this would also make sense for UML.
Thanks, //richard
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