From owner-svn-src-head@freebsd.org Thu Oct 15 11:44:28 2020 Return-Path: Delivered-To: svn-src-head@mailman.nyi.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mailman.nyi.freebsd.org (Postfix) with ESMTP id CF9E343B07E; Thu, 15 Oct 2020 11:44:28 +0000 (UTC) (envelope-from whu@FreeBSD.org) Received: from mxrelay.nyi.freebsd.org (mxrelay.nyi.freebsd.org [IPv6:2610:1c1:1:606c::19:3]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256 client-signature RSA-PSS (4096 bits) client-digest SHA256) (Client CN "mxrelay.nyi.freebsd.org", Issuer "Let's Encrypt Authority X3" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id 4CBnWJ57y3z4NqR; Thu, 15 Oct 2020 11:44:28 +0000 (UTC) (envelope-from whu@FreeBSD.org) Received: from repo.freebsd.org (repo.freebsd.org [IPv6:2610:1c1:1:6068::e6a:0]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by mxrelay.nyi.freebsd.org (Postfix) with ESMTPS id 93E271F076; Thu, 15 Oct 2020 11:44:28 +0000 (UTC) (envelope-from whu@FreeBSD.org) Received: from repo.freebsd.org ([127.0.1.37]) by repo.freebsd.org (8.15.2/8.15.2) with ESMTP id 09FBiSFj088173; Thu, 15 Oct 2020 11:44:28 GMT (envelope-from whu@FreeBSD.org) Received: (from whu@localhost) by repo.freebsd.org (8.15.2/8.15.2/Submit) id 09FBiSNV088172; Thu, 15 Oct 2020 11:44:28 GMT (envelope-from whu@FreeBSD.org) Message-Id: <202010151144.09FBiSNV088172@repo.freebsd.org> X-Authentication-Warning: repo.freebsd.org: whu set sender to whu@FreeBSD.org using -f From: Wei Hu Date: Thu, 15 Oct 2020 11:44:28 +0000 (UTC) To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r366721 - head/sys/dev/hyperv/netvsc X-SVN-Group: head X-SVN-Commit-Author: whu X-SVN-Commit-Paths: head/sys/dev/hyperv/netvsc X-SVN-Commit-Revision: 366721 X-SVN-Commit-Repository: base MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-BeenThere: svn-src-head@freebsd.org X-Mailman-Version: 2.1.33 Precedence: list List-Id: SVN commit messages for the src tree for head/-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 15 Oct 2020 11:44:28 -0000 Author: whu Date: Thu Oct 15 11:44:28 2020 New Revision: 366721 URL: https://svnweb.freebsd.org/changeset/base/366721 Log: Hyper-V: hn: Relinquish cpu in HN_LOCK to avoid deadlock The try lock loop in HN_LOCK put the thread spinning on cpu if the lock is not available. It is possible to cause deadlock if the thread holding the lock is sleeping. Relinquish the cpu to work around this problem even it doesn't completely solve the issue. The priority inversion could cause the livelock no matter how less likely it could happen. A more complete solution may be needed in the future. Reported by: Microsoft, Netapp MFC after: 2 weeks Sponsored by: Microsoft Modified: head/sys/dev/hyperv/netvsc/if_hn.c Modified: head/sys/dev/hyperv/netvsc/if_hn.c ============================================================================== --- head/sys/dev/hyperv/netvsc/if_hn.c Thu Oct 15 05:57:20 2020 (r366720) +++ head/sys/dev/hyperv/netvsc/if_hn.c Thu Oct 15 11:44:28 2020 (r366721) @@ -71,8 +71,10 @@ __FBSDID("$FreeBSD$"); #include #include #include +#include #include #include +#include #include #include #include @@ -165,8 +167,11 @@ __FBSDID("$FreeBSD$"); #define HN_LOCK_ASSERT(sc) sx_assert(&(sc)->hn_lock, SA_XLOCKED) #define HN_LOCK(sc) \ do { \ - while (sx_try_xlock(&(sc)->hn_lock) == 0) \ + while (sx_try_xlock(&(sc)->hn_lock) == 0) { \ + /* Relinquish cpu to avoid deadlock */ \ + sched_relinquish(curthread); \ DELAY(1000); \ + } \ } while (0) #define HN_UNLOCK(sc) sx_xunlock(&(sc)->hn_lock)