From mboxrd@z Thu Jan 1 00:00:00 1970 From: Konrad Rzeszutek Wilk Subject: [PATCH 10/10] xen/mmu: Warn against races. Date: Tue, 21 Dec 2010 16:37:40 -0500 Message-ID: <1292967460-15709-11-git-send-email-konrad.wilk@oracle.com> References: <1292967460-15709-1-git-send-email-konrad.wilk@oracle.com> Return-path: In-Reply-To: <1292967460-15709-1-git-send-email-konrad.wilk@oracle.com> Sender: linux-kernel-owner@vger.kernel.org To: linux-kernel@vger.kernel.org, jeremy@goop.org, hpa@zytor.com Cc: Jan Beulich , xen-devel@lists.xensource.com, Konrad Rzeszutek Wilk , Konrad Rzeszutek Wilk List-Id: xen-devel@lists.xenproject.org The initial bootup code uses set_phys_to_machine quite a lot, and after bootup it would be the balloon driver. The balloon driver does have mutex lock so this should not be necessary - but just in case, add a warning if we do hit this scenario. Signed-off-by: Konrad Rzeszutek Wilk --- arch/x86/xen/mmu.c | 8 +++++--- 1 files changed, 5 insertions(+), 3 deletions(-) diff --git a/arch/x86/xen/mmu.c b/arch/x86/xen/mmu.c index b2b8733..86d3bd3 100644 --- a/arch/x86/xen/mmu.c +++ b/arch/x86/xen/mmu.c @@ -549,13 +549,15 @@ bool __set_phys_to_machine(unsigned long pfn, unsigned long mfn) idx = p2m_index(pfn); if (mfn == INVALID_P2M_ENTRY) { - /* If it is INVALID, swap over.. */ + /* Ballon lock should inhibit racing, but just in case.*/ if (p2m_top[topidx] == p2m_mid_identity) { - p2m_top[topidx] = p2m_mid_missing; + WARN_ON(cmpxchg(&p2m_top[topidx], p2m_mid_identity, + p2m_mid_missing) != p2m_mid_identity); return 1; } if (p2m_top[topidx][mididx] == p2m_identity) { - p2m_top[topidx][mididx] = p2m_missing; + WARN_ON(cmpxchg(&p2m_top[topidx][mididx], p2m_identity, + p2m_missing) != p2m_identity); return 1; } } -- 1.7.1