From: Andrew Morton <akpm@linux-foundation.org> To: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: Shan Hai <haishan.bai@gmail.com>, Peter Zijlstra <peterz@infradead.org>, Peter Zijlstra <a.p.zijlstra@chello.nl>, paulus@samba.org, tglx@linutronix.de, walken@google.com, dhowells@redhat.com, cmetcalf@tilera.com, tony.luck@intel.com, linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org Subject: Re: [RFC/PATCH] mm/futex: Fix futex writes on archs with SW tracking of dirty & young Date: Thu, 21 Jul 2011 15:36:06 -0700 [thread overview] Message-ID: <20110721153606.37e6f432.akpm@linux-foundation.org> (raw) In-Reply-To: <1311049762.25044.392.camel@pasglop> On Tue, 19 Jul 2011 14:29:22 +1000 Benjamin Herrenschmidt <benh@kernel.crashing.org> wrote: > The futex code currently attempts to write to user memory within > a pagefault disabled section, and if that fails, tries to fix it > up using get_user_pages(). > > This doesn't work on archs where the dirty and young bits are > maintained by software, since they will gate access permission > in the TLB, and will not be updated by gup(). > > In addition, there's an expectation on some archs that a > spurious write fault triggers a local TLB flush, and that is > missing from the picture as well. > > I decided that adding those "features" to gup() would be too much > for this already too complex function, and instead added a new > simpler fixup_user_fault() which is essentially a wrapper around > handle_mm_fault() which the futex code can call. > > Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org> > --- > > Shan, can you test this ? It might not fix the problem um, what problem. There's no description here of the user-visible effects of the bug hence it's hard to work out what kernel version(s) should receive this patch. What kernel version(s) should receive this patch? > since I'm > starting to have the nasty feeling that you are hitting what is > somewhat a subtly different issue or my previous patch should > have worked (but then I might have done a stupid mistake as well) > but let us know anyway. I assume that Shan reported the secret problem so I added the reported-by to the changelog.
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From: Andrew Morton <akpm@linux-foundation.org> To: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: tony.luck@intel.com, Peter Zijlstra <a.p.zijlstra@chello.nl>, Shan Hai <haishan.bai@gmail.com>, Peter Zijlstra <peterz@infradead.org>, linux-kernel@vger.kernel.org, cmetcalf@tilera.com, dhowells@redhat.com, paulus@samba.org, tglx@linutronix.de, walken@google.com, linuxppc-dev@lists.ozlabs.org Subject: Re: [RFC/PATCH] mm/futex: Fix futex writes on archs with SW tracking of dirty & young Date: Thu, 21 Jul 2011 15:36:06 -0700 [thread overview] Message-ID: <20110721153606.37e6f432.akpm@linux-foundation.org> (raw) In-Reply-To: <1311049762.25044.392.camel@pasglop> On Tue, 19 Jul 2011 14:29:22 +1000 Benjamin Herrenschmidt <benh@kernel.crashing.org> wrote: > The futex code currently attempts to write to user memory within > a pagefault disabled section, and if that fails, tries to fix it > up using get_user_pages(). > > This doesn't work on archs where the dirty and young bits are > maintained by software, since they will gate access permission > in the TLB, and will not be updated by gup(). > > In addition, there's an expectation on some archs that a > spurious write fault triggers a local TLB flush, and that is > missing from the picture as well. > > I decided that adding those "features" to gup() would be too much > for this already too complex function, and instead added a new > simpler fixup_user_fault() which is essentially a wrapper around > handle_mm_fault() which the futex code can call. > > Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org> > --- > > Shan, can you test this ? It might not fix the problem um, what problem. There's no description here of the user-visible effects of the bug hence it's hard to work out what kernel version(s) should receive this patch. What kernel version(s) should receive this patch? > since I'm > starting to have the nasty feeling that you are hitting what is > somewhat a subtly different issue or my previous patch should > have worked (but then I might have done a stupid mistake as well) > but let us know anyway. I assume that Shan reported the secret problem so I added the reported-by to the changelog.
next prev parent reply other threads:[~2011-07-21 22:36 UTC|newest] Thread overview: 138+ messages / expand[flat|nested] mbox.gz Atom feed top 2011-07-15 8:07 [PATCH 0/1] Fixup write permission of TLB on powerpc e500 core Shan Hai 2011-07-15 8:07 ` Shan Hai 2011-07-15 8:07 ` [PATCH 1/1] " Shan Hai 2011-07-15 8:07 ` Shan Hai 2011-07-15 10:23 ` Peter Zijlstra 2011-07-15 10:23 ` Peter Zijlstra 2011-07-15 15:18 ` Shan Hai 2011-07-15 15:18 ` Shan Hai 2011-07-15 15:24 ` Peter Zijlstra 2011-07-15 15:24 ` Peter Zijlstra 2011-07-16 15:36 ` Shan Hai 2011-07-16 15:36 ` Shan Hai 2011-07-16 14:50 ` Shan Hai 2011-07-16 14:50 ` Shan Hai 2011-07-16 23:49 ` Benjamin Herrenschmidt 2011-07-16 23:49 ` Benjamin Herrenschmidt 2011-07-17 9:38 ` Peter Zijlstra 2011-07-17 9:38 ` Peter Zijlstra 2011-07-17 14:29 ` Benjamin Herrenschmidt 2011-07-17 14:29 ` Benjamin Herrenschmidt 2011-07-17 23:14 ` Benjamin Herrenschmidt 2011-07-17 23:14 ` Benjamin Herrenschmidt 2011-07-18 3:53 ` Benjamin Herrenschmidt 2011-07-18 3:53 ` Benjamin Herrenschmidt 2011-07-18 4:02 ` Benjamin Herrenschmidt 2011-07-18 4:02 ` Benjamin Herrenschmidt 2011-07-18 4:01 ` Benjamin Herrenschmidt 2011-07-18 4:01 ` Benjamin Herrenschmidt 2011-07-18 6:48 ` Shan Hai 2011-07-18 6:48 ` Shan Hai 2011-07-18 7:01 ` Benjamin Herrenschmidt 2011-07-18 7:01 ` Benjamin Herrenschmidt 2011-07-18 7:26 ` Shan Hai 2011-07-18 7:26 ` Shan Hai 2011-07-18 7:36 ` Benjamin Herrenschmidt 2011-07-18 7:36 ` Benjamin Herrenschmidt 2011-07-18 7:50 ` Shan Hai 2011-07-18 7:50 ` Shan Hai 2011-07-19 3:30 ` Shan Hai 2011-07-19 3:30 ` Shan Hai 2011-07-19 4:20 ` Benjamin Herrenschmidt 2011-07-19 4:20 ` Benjamin Herrenschmidt 2011-07-19 4:29 ` [RFC/PATCH] mm/futex: Fix futex writes on archs with SW tracking of dirty & young Benjamin Herrenschmidt 2011-07-19 4:29 ` Benjamin Herrenschmidt 2011-07-19 4:55 ` Shan Hai 2011-07-19 4:55 ` Shan Hai 2011-07-19 5:17 ` Shan Hai 2011-07-19 5:17 ` Shan Hai 2011-07-19 5:24 ` Benjamin Herrenschmidt 2011-07-19 5:24 ` Benjamin Herrenschmidt 2011-07-19 5:38 ` Shan Hai 2011-07-19 5:38 ` Shan Hai 2011-07-19 7:46 ` Benjamin Herrenschmidt 2011-07-19 7:46 ` Benjamin Herrenschmidt 2011-07-19 8:24 ` Shan Hai 2011-07-19 8:24 ` Shan Hai 2011-07-19 8:26 ` [RFC/PATCH] mm/futex: Fix futex writes on archs with SW trackingof " David Laight 2011-07-19 8:26 ` David Laight 2011-07-19 8:45 ` Benjamin Herrenschmidt 2011-07-19 8:45 ` Benjamin Herrenschmidt 2011-07-19 8:45 ` Shan Hai 2011-07-19 8:45 ` Shan Hai 2011-07-19 11:10 ` [RFC/PATCH] mm/futex: Fix futex writes on archs with SW tracking of " Peter Zijlstra 2011-07-19 11:10 ` Peter Zijlstra 2011-07-20 14:39 ` Darren Hart 2011-07-20 14:39 ` Darren Hart 2011-07-21 22:36 ` Andrew Morton [this message] 2011-07-21 22:36 ` Andrew Morton 2011-07-21 22:52 ` Benjamin Herrenschmidt 2011-07-21 22:52 ` Benjamin Herrenschmidt 2011-07-21 22:57 ` Benjamin Herrenschmidt 2011-07-21 22:57 ` Benjamin Herrenschmidt 2011-07-21 22:59 ` Andrew Morton 2011-07-21 22:59 ` Andrew Morton 2011-07-22 1:40 ` Benjamin Herrenschmidt 2011-07-22 1:40 ` Benjamin Herrenschmidt 2011-07-22 1:54 ` Shan Hai 2011-07-22 1:54 ` Shan Hai 2011-07-27 6:50 ` Mike Frysinger 2011-07-27 6:50 ` Mike Frysinger 2011-07-27 7:58 ` Benjamin Herrenschmidt 2011-07-27 7:58 ` Benjamin Herrenschmidt 2011-07-27 8:59 ` Peter Zijlstra 2011-07-27 8:59 ` Peter Zijlstra 2011-07-27 10:09 ` David Howells 2011-07-27 10:09 ` David Howells 2011-07-27 10:17 ` Peter Zijlstra 2011-07-27 10:17 ` Peter Zijlstra 2011-07-27 10:20 ` Benjamin Herrenschmidt 2011-07-27 10:20 ` Benjamin Herrenschmidt 2011-07-28 0:12 ` Mike Frysinger 2011-07-28 0:12 ` Mike Frysinger 2011-08-08 2:31 ` Mike Frysinger 2011-08-08 2:31 ` Mike Frysinger 2011-07-28 10:55 ` David Howells 2011-07-28 10:55 ` David Howells 2011-07-17 11:02 ` [PATCH 1/1] Fixup write permission of TLB on powerpc e500 core Peter Zijlstra 2011-07-17 11:02 ` Peter Zijlstra 2011-07-17 13:33 ` Shan Hai 2011-07-17 13:33 ` Shan Hai 2011-07-17 14:48 ` Benjamin Herrenschmidt 2011-07-17 14:48 ` Benjamin Herrenschmidt 2011-07-17 15:40 ` Shan Hai 2011-07-17 15:40 ` Shan Hai 2011-07-17 22:34 ` Benjamin Herrenschmidt 2011-07-17 22:34 ` Benjamin Herrenschmidt 2011-07-17 14:34 ` Benjamin Herrenschmidt 2011-07-17 14:34 ` Benjamin Herrenschmidt 2011-07-15 8:20 ` [PATCH 0/1] " Peter Zijlstra 2011-07-15 8:20 ` Peter Zijlstra 2011-07-15 8:38 ` MailingLists 2011-07-15 8:38 ` MailingLists 2011-07-15 8:44 ` Peter Zijlstra 2011-07-15 8:44 ` Peter Zijlstra 2011-07-15 9:08 ` Shan Hai 2011-07-15 9:08 ` Shan Hai 2011-07-15 9:12 ` Benjamin Herrenschmidt 2011-07-15 9:12 ` Benjamin Herrenschmidt 2011-07-15 9:50 ` Peter Zijlstra 2011-07-15 9:50 ` Peter Zijlstra 2011-07-15 10:06 ` Shan Hai 2011-07-15 10:06 ` Shan Hai 2011-07-15 10:32 ` David Laight 2011-07-15 10:32 ` David Laight 2011-07-15 10:39 ` Peter Zijlstra 2011-07-15 10:39 ` Peter Zijlstra 2011-07-15 15:32 ` Shan Hai 2011-07-15 15:32 ` Shan Hai 2011-07-16 0:20 ` Benjamin Herrenschmidt 2011-07-16 0:20 ` Benjamin Herrenschmidt 2011-07-16 15:03 ` Shan Hai 2011-07-16 15:03 ` Shan Hai 2011-07-15 23:47 ` Benjamin Herrenschmidt 2011-07-15 23:47 ` Benjamin Herrenschmidt 2011-07-15 9:07 ` Benjamin Herrenschmidt 2011-07-15 9:07 ` Benjamin Herrenschmidt 2011-07-15 9:05 ` Benjamin Herrenschmidt 2011-07-15 9:05 ` Benjamin Herrenschmidt
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