From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id E7D55C43143 for ; Mon, 1 Oct 2018 07:38:15 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 9BB192089D for ; Mon, 1 Oct 2018 07:38:15 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 9BB192089D Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=suse.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728902AbeJAOOh (ORCPT ); Mon, 1 Oct 2018 10:14:37 -0400 Received: from mx2.suse.de ([195.135.220.15]:32986 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1728731AbeJAOOh (ORCPT ); Mon, 1 Oct 2018 10:14:37 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay1.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 11151ADCE; Mon, 1 Oct 2018 07:38:12 +0000 (UTC) Subject: Re: [PATCH 2/2] xen: make xen_qlock_wait() nestable To: linux-kernel@vger.kernel.org, xen-devel@lists.xenproject.org, x86@kernel.org Cc: boris.ostrovsky@oracle.com, hpa@zytor.com, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, stable@vger.kernel.org, Waiman Long , peterz@infradead.org References: <20181001071641.19282-1-jgross@suse.com> <20181001071641.19282-3-jgross@suse.com> From: Juergen Gross Openpgp: preference=signencrypt Autocrypt: addr=jgross@suse.com; prefer-encrypt=mutual; keydata= xsBNBFOMcBYBCACgGjqjoGvbEouQZw/ToiBg9W98AlM2QHV+iNHsEs7kxWhKMjrioyspZKOB ycWxw3ie3j9uvg9EOB3aN4xiTv4qbnGiTr3oJhkB1gsb6ToJQZ8uxGq2kaV2KL9650I1SJve dYm8Of8Zd621lSmoKOwlNClALZNew72NjJLEzTalU1OdT7/i1TXkH09XSSI8mEQ/ouNcMvIJ NwQpd369y9bfIhWUiVXEK7MlRgUG6MvIj6Y3Am/BBLUVbDa4+gmzDC9ezlZkTZG2t14zWPvx XP3FAp2pkW0xqG7/377qptDmrk42GlSKN4z76ELnLxussxc7I2hx18NUcbP8+uty4bMxABEB AAHNHkp1ZXJnZW4gR3Jvc3MgPGpncm9zc0BzdXNlLmRlPsLAeQQTAQIAIwUCU4xw6wIbAwcL CQgHAwIBBhUIAgkKCwQWAgMBAh4BAheAAAoJELDendYovxMvi4UH/Ri+OXlObzqMANruTd4N zmVBAZgx1VW6jLc8JZjQuJPSsd/a+bNr3BZeLV6lu4Pf1Yl2Log129EX1KWYiFFvPbIiq5M5 kOXTO8Eas4CaScCvAZ9jCMQCgK3pFqYgirwTgfwnPtxFxO/F3ZcS8jovza5khkSKL9JGq8Nk czDTruQ/oy0WUHdUr9uwEfiD9yPFOGqp4S6cISuzBMvaAiC5YGdUGXuPZKXLpnGSjkZswUzY d9BVSitRL5ldsQCg6GhDoEAeIhUC4SQnT9SOWkoDOSFRXZ+7+WIBGLiWMd+yKDdRG5RyP/8f 3tgGiB6cyuYfPDRGsELGjUaTUq3H2xZgIPfOwE0EU4xwFgEIAMsx+gDjgzAY4H1hPVXgoLK8 B93sTQFN9oC6tsb46VpxyLPfJ3T1A6Z6MVkLoCejKTJ3K9MUsBZhxIJ0hIyvzwI6aYJsnOew cCiCN7FeKJ/oA1RSUemPGUcIJwQuZlTOiY0OcQ5PFkV5YxMUX1F/aTYXROXgTmSaw0aC1Jpo w7Ss1mg4SIP/tR88/d1+HwkJDVW1RSxC1PWzGizwRv8eauImGdpNnseneO2BNWRXTJumAWDD pYxpGSsGHXuZXTPZqOOZpsHtInFyi5KRHSFyk2Xigzvh3b9WqhbgHHHE4PUVw0I5sIQt8hJq 5nH5dPqz4ITtCL9zjiJsExHuHKN3NZsAEQEAAcLAXwQYAQIACQUCU4xwFgIbDAAKCRCw3p3W KL8TL0P4B/9YWver5uD/y/m0KScK2f3Z3mXJhME23vGBbMNlfwbr+meDMrJZ950CuWWnQ+d+ Ahe0w1X7e3wuLVODzjcReQ/v7b4JD3wwHxe+88tgB9byc0NXzlPJWBaWV01yB2/uefVKryAf AHYEd0gCRhx7eESgNBe3+YqWAQawunMlycsqKa09dBDL1PFRosF708ic9346GLHRc6Vj5SRA UTHnQqLetIOXZm3a2eQ1gpQK9MmruO86Vo93p39bS1mqnLLspVrL4rhoyhsOyh0Hd28QCzpJ wKeHTd0MAWAirmewHXWPco8p1Wg+V+5xfZzuQY0f4tQxvOpXpt4gQ1817GQ5/Ed/wsDtBBgB CAAgFiEEhRJncuj2BJSl0Jf3sN6d1ii/Ey8FAlrd8NACGwIAgQkQsN6d1ii/Ey92IAQZFggA HRYhBFMtsHpB9jjzHji4HoBcYbtP2GO+BQJa3fDQAAoJEIBcYbtP2GO+TYsA/30H/0V6cr/W V+J/FCayg6uNtm3MJLo4rE+o4sdpjjsGAQCooqffpgA+luTT13YZNV62hAnCLKXH9n3+ZAgJ RtAyDWk1B/0SMDVs1wxufMkKC3Q/1D3BYIvBlrTVKdBYXPxngcRoqV2J77lscEvkLNUGsu/z W2pf7+P3mWWlrPMJdlbax00vevyBeqtqNKjHstHatgMZ2W0CFC4hJ3YEetuRBURYPiGzuJXU pAd7a7BdsqWC4o+GTm5tnGrCyD+4gfDSpkOT53S/GNO07YkPkm/8J4OBoFfgSaCnQ1izwgJQ jIpcG2fPCI2/hxf2oqXPYbKr1v4Z1wthmoyUgGN0LPTIm+B5vdY82wI5qe9uN6UOGyTH2B3p hRQUWqCwu2sqkI3LLbTdrnyDZaixT2T0f4tyF5Lfs+Ha8xVMhIyzNb1byDI5FKCb Message-ID: <8ae7807d-9f0d-e6f2-ef0d-9dce56d06165@suse.com> Date: Mon, 1 Oct 2018 09:38:11 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.0 MIME-Version: 1.0 In-Reply-To: <20181001071641.19282-3-jgross@suse.com> Content-Type: text/plain; charset=utf-8 Content-Language: de-DE Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Correcting Waiman's mail address On 01/10/2018 09:16, Juergen Gross wrote: > xen_qlock_wait() isn't safe for nested calls due to interrupts. A call > of xen_qlock_kick() might be ignored in case a deeper nesting level > was active right before the call of xen_poll_irq(): > > CPU 1: CPU 2: > spin_lock(lock1) > spin_lock(lock1) > -> xen_qlock_wait() > -> xen_clear_irq_pending() > Interrupt happens > spin_unlock(lock1) > -> xen_qlock_kick(CPU 2) > spin_lock_irqsave(lock2) > spin_lock_irqsave(lock2) > -> xen_qlock_wait() > -> xen_clear_irq_pending() > clears kick for lock1 > -> xen_poll_irq() > spin_unlock_irq_restore(lock2) > -> xen_qlock_kick(CPU 2) > wakes up > spin_unlock_irq_restore(lock2) > IRET > resumes in xen_qlock_wait() > -> xen_poll_irq() > never wakes up > > The solution is to disable interrupts in xen_qlock_wait() and not to > poll for the irq in case xen_qlock_wait() is called in nmi context. > > Cc: stable@vger.kernel.org > Cc: longman@redhat.com > Cc: peterz@infradead.org > Signed-off-by: Juergen Gross > --- > arch/x86/xen/spinlock.c | 24 ++++++++++-------------- > 1 file changed, 10 insertions(+), 14 deletions(-) > > diff --git a/arch/x86/xen/spinlock.c b/arch/x86/xen/spinlock.c > index cd210a4ba7b1..e8d880e98057 100644 > --- a/arch/x86/xen/spinlock.c > +++ b/arch/x86/xen/spinlock.c > @@ -39,29 +39,25 @@ static void xen_qlock_kick(int cpu) > */ > static void xen_qlock_wait(u8 *byte, u8 val) > { > + unsigned long flags; > int irq = __this_cpu_read(lock_kicker_irq); > > /* If kicker interrupts not initialized yet, just spin */ > - if (irq == -1) > + if (irq == -1 || in_nmi()) > return; > > - /* If irq pending already clear it and return. */ > + /* Guard against reentry. */ > + local_irq_save(flags); > + > + /* If irq pending already clear it. */ > if (xen_test_irq_pending(irq)) { > xen_clear_irq_pending(irq); > - return; > + } else if (READ_ONCE(*byte) == val) { > + /* Block until irq becomes pending (or a spurious wakeup) */ > + xen_poll_irq(irq); > } > > - if (READ_ONCE(*byte) != val) > - return; > - > - /* > - * If an interrupt happens here, it will leave the wakeup irq > - * pending, which will cause xen_poll_irq() to return > - * immediately. > - */ > - > - /* Block until irq becomes pending (or perhaps a spurious wakeup) */ > - xen_poll_irq(irq); > + local_irq_restore(flags); > } > > static irqreturn_t dummy_handler(int irq, void *dev_id) >