lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
Open Source and information security mailing list archives
| ||
|
Message-ID: <1267550787.19491.109.camel@nseg_linux_HP1.broadcom.com> Date: Tue, 2 Mar 2010 09:26:27 -0800 From: "Michael Chan" <mchan@...adcom.com> To: "Stanislaw Gruszka" <sgruszka@...hat.com> cc: "Vladislav Zolotarov" <vladz@...adcom.com>, "netdev@...r.kernel.org" <netdev@...r.kernel.org>, "davem@...emloft.net" <davem@...emloft.net>, "Eilon Greenstein" <eilong@...adcom.com>, "Matthew Carlson" <mcarlson@...adcom.com> Subject: Re: [PATCH 1/1] bnx2x: Tx barriers and locks On Tue, 2010-03-02 at 08:59 -0800, Stanislaw Gruszka wrote: > On Tue, Mar 02, 2010 at 08:18:44AM -0800, Michael Chan wrote: > > Stanislaw Gruszka wrote: > > > > > On Tue, Mar 02, 2010 at 04:50:59AM -0800, Vladislav Zolotarov wrote: > > > > Stanislaw barrier() is not a memory barrier - it's a > > > compiler barrier. I don't think removing it from > > > bnx2x_tx_avail() will improve anything. If u think I'm wrong, > > > could u, pls., provide a specific example. > > > > > > Only improvement is removing confusing code, And comment like > > > "Tell compiler that prod and cons can change" is even more > > > confusing. If you think I'm wrong, just tell as why that > > > barrier is needed :) > > > > The barrier (compiler barrier at least) is required in > > bnx2x_tx_avail(). The status block index can be updated by DMA and > > the compiler doesn't know it (because it is considered wrong to > > If you are telling status block index you mean which variable ? The fp-> fields which can be updated by NAPI poll based on new status block DMA. > > > declare the status block as volatile). Near the end of > > bnx2x_start_xmit() where we call bnx2x_tx_avail() twice. It is > > possible that the compiler will optimize it and not look at the > > status block in memory the second time. > > Ok, I'm trying to understand. > -- -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Powered by blists - more mailing lists