Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757587AbXJCTzt (ORCPT ); Wed, 3 Oct 2007 15:55:49 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754697AbXJCTzm (ORCPT ); Wed, 3 Oct 2007 15:55:42 -0400 Received: from narury.org ([84.16.240.217]:34160 "EHLO narury.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754693AbXJCTzl (ORCPT ); Wed, 3 Oct 2007 15:55:41 -0400 X-Greylist: delayed 1311 seconds by postgrey-1.27 at vger.kernel.org; Wed, 03 Oct 2007 15:55:40 EDT Date: Wed, 3 Oct 2007 22:33:46 +0300 From: Riku Voipio To: linux-kernel@vger.kernel.org Cc: Mikael Pettersson , Lennert Buytenhek Subject: [PATCH][RFC] unbreak generic futex_atomic_cmpxchg_inatomic() on UP Message-ID: <20071003193346.GA3750@kos.to> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii; x-action=pgp-signed Content-Disposition: inline In-Reply-To: <200708012300.l71N0LRX008930@harpo.it.uu.se> X-message-flag: Warning: message not sent with a DRM-Certified client User-Agent: Mutt/1.5.11+cvs20060126 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2751 Lines: 91 -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 What's the state of this patch? I can confirm tst-robust1 from glibc testsuite locks a armv5 machine hard. With this patch applied, the test succeeds. > The higher-end archs (x86, sparc64, ppc64, etc) provide fully-functional > asm/futex.h implementations, but a number of archs (alpha, arm, arm26, > avr32, blackfin, cris, h8300, m32r, m68k, mk68knommu, sh64, sparc, um, > v850, and xtensa) use asm-generic/futex.h, which makes robust futexes > horribly broken on them. There have also been reports recently that PI > futexes are broken due to the generic futex_atomic_cmpxchg_inatomic() > just being an -ENOSYS stub. This an effective local DOS bug on the affected architectures, too.. > The patch below implements the generic futex_atomic_cmpxchg_inatomic() in > terms of __copy_{from,to}_user_inatomic() and preempt_{disable,enable}(). > It obviously doesn't support SMP, but UP-only support should go a long > way for users of the affected archs. > > I'm using this patch now and it has allowed me to build and use glibc-2.4 > with NPTL on ARM (glibc-2.4-11.src.rpm from FC5 + ARM fixes). > (Finally I can ditch LinuxThreads :->) > > Comments? > > /Mikael > > --- linux-2.6.22/include/asm-generic/futex.h.~1~ 2007-02-04 19:44:54.000000000 +0100 > +++ linux-2.6.22/include/asm-generic/futex.h 2007-08-01 19:03:43.000000000 +0200 > @@ -4,6 +4,7 @@ > #ifdef __KERNEL__ > > #include > +#include > #include > #include > > @@ -52,7 +53,34 @@ futex_atomic_op_inuser (int encoded_op, > static inline int > futex_atomic_cmpxchg_inatomic(int __user *uaddr, int oldval, int newval) > { > +#ifdef CONFIG_SMP > return -ENOSYS; > +#else > + int curval, ret; > + > + if (!access_ok(VERIFY_WRITE, uaddr, sizeof(int))) > + return -EFAULT; > + > + preempt_disable(); > + > + ret = -EFAULT; > + if (__copy_from_user_inatomic(&curval, uaddr, sizeof(int))) > + goto out; > + > + ret = curval; > + if (curval != oldval) > + goto out; > + > + ret = -EFAULT; > + if (__copy_to_user_inatomic(uaddr, &newval, sizeof(int))) > + goto out; > + > + ret = newval; > + > + out: > + preempt_enable(); > + return ret; > +#endif > } > > #endif > - - -- "rm -rf" only sounds scary if you don't have backups -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.6 (GNU/Linux) iD8DBQFHA+6aibPvMsrqrwMRAlMuAKCBf7qpD2dETgU+RgnDG4ArVvFp3gCgrewq 4KvOt40U1MAPM7g4F/Ps5jk= =68gr -----END PGP SIGNATURE----- - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/