From mboxrd@z Thu Jan 1 00:00:00 1970 From: Joerg Roedel Subject: Re: [PATCH 08/16] dma-debug: add core checking functions Date: Wed, 14 Jan 2009 12:44:01 +0100 Message-ID: <20090114114401.GL20283@amd.com> References: <1231517970-20288-1-git-send-email-joerg.roedel@amd.com> <1231517970-20288-9-git-send-email-joerg.roedel@amd.com> <20090110231127.GK17917@elte.hu> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: linux-kernel@vger.kernel.org, mingo@redhat.com, dwmw2@infradead.org, fujita.tomonori@lab.ntt.co.jp, netdev@vger.kernel.org, iommu@lists.linux-foundation.org To: Ingo Molnar Return-path: Content-Disposition: inline In-Reply-To: <20090110231127.GK17917@elte.hu> Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org On Sun, Jan 11, 2009 at 12:11:27AM +0100, Ingo Molnar wrote: >=20 > * Joerg Roedel wrote: >=20 > > +#define err_printk(dev, format, arg...) do { \ > > + error_count +=3D 1; \ > > + if (show_all_errors || show_num_errors > 0) { \ > > + WARN(1, "%s %s: " format, \ > > + dev_driver_string(dev), \ > > + dev_name(dev) , ## arg); \ > > + } \ > > + if (!show_all_errors && show_num_errors > 0) \ > > + show_num_errors -=3D 1; \ >=20 > Note that the arithmetics here is SMP-unsafe: we only hold the hash b= ucket=20 > so if two errors hit at once on two CPUs then the error tracking vari= ables=20 > can be accessed at once. >=20 > I'd suggest a simple global lock for this error case (taken inside th= e=20 > hash bucket lock), to be on the safe side. As I wrote in a previous email, a race here is no big deal. I add a comment to document it. Or do we want another global lock here? > Also, please dont use a macro for this - printk details can be passed= in=20 > to helper inlines/functions too. Hmm, how does this look like? There is not WARN variant which can use va_args as a parameter. And it is important that the error message is logged in the warning itself. So the driver developer can see it when a user reports the warning. Joerg --=20 | Advanced Micro Devices GmbH Operating | Karl-Hammerschmidt-Str. 34, 85609 Dornach bei M=C3=BCnchen System |=20 Research | Gesch=C3=A4ftsf=C3=BChrer: Jochen Polster, Thomas M. McCoy= , Giuliano Meroni Center | Sitz: Dornach, Gemeinde Aschheim, Landkreis M=C3=BCnchen | Registergericht M=C3=BCnchen, HRB Nr. 43632