Return-Path: linux-nfs-owner@vger.kernel.org Received: from e3.ny.us.ibm.com ([32.97.182.143]:33197 "EHLO e3.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932392Ab2JBVnj (ORCPT ); Tue, 2 Oct 2012 17:43:39 -0400 Received: from /spool/local by e3.ny.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Tue, 2 Oct 2012 17:43:38 -0400 Date: Tue, 2 Oct 2012 14:43:27 -0700 From: Nishanth Aravamudan To: Benjamin Herrenschmidt Cc: Alexander Graf , linux-nfs@vger.kernel.org, Jan Kara , Linus Torvalds , LKML List , "J. Bruce Fields" , anton@samba.org, skinsbursky@parallels.com, bfields@redhat.com, linuxppc-dev Subject: Re: [REGRESSION] nfsd crashing with 3.6.0-rc7 on PowerPC Message-ID: <20121002214327.GA29218@linux.vnet.ibm.com> References: <3BDA9E62-7031-42D6-8CA9-5327B61700F5@suse.de> <20120928151043.GA19102@fieldses.org> <2A52FC96-148C-4F7A-9950-E152E0C6698D@suse.de> <1349139509.3847.2.camel@pasglop> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <1349139509.3847.2.camel@pasglop> Sender: linux-nfs-owner@vger.kernel.org List-ID: Hi Ben, On 02.10.2012 [10:58:29 +1000], Benjamin Herrenschmidt wrote: > On Mon, 2012-10-01 at 16:03 +0200, Alexander Graf wrote: > > Phew. Here we go :). It looks to be more of a PPC specific problem > > than it appeared as at first: > > Ok, so I suspect the problem is the pushing down of the locks which > breaks with iommu backends that have a separate flush callback. In > that case, the flush moves out of the allocator lock. > > Now we do call flush before we return, still, but it becomes racy > I suspect, but somebody needs to give it a closer look. I'm hoping > Anton or Nish will later today. Started looking into this. If your suspicion were accurate, wouldn't the bisection have stopped at 0e4bc95d87394364f408627067238453830bdbf3 ("powerpc/iommu: Reduce spinlock coverage in iommu_alloc and iommu_free")? Alex, the error is reproducible, right? Does it go away by reverting that commit against mainline? Just trying to narrow down my focus. Thanks, Nish