From owner-svn-src-all@FreeBSD.ORG Fri Dec 19 15:24:18 2008 Return-Path: Delivered-To: svn-src-all@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id EEC531065677; Fri, 19 Dec 2008 15:24:18 +0000 (UTC) (envelope-from kib@FreeBSD.org) Received: from svn.freebsd.org (svn.freebsd.org [IPv6:2001:4f8:fff6::2c]) by mx1.freebsd.org (Postfix) with ESMTP id DE0A48FC1E; Fri, 19 Dec 2008 15:24:18 +0000 (UTC) (envelope-from kib@FreeBSD.org) Received: from svn.freebsd.org (localhost [127.0.0.1]) by svn.freebsd.org (8.14.3/8.14.3) with ESMTP id mBJFOIxP075548; Fri, 19 Dec 2008 15:24:18 GMT (envelope-from kib@svn.freebsd.org) Received: (from kib@localhost) by svn.freebsd.org (8.14.3/8.14.3/Submit) id mBJFOIMj075547; Fri, 19 Dec 2008 15:24:18 GMT (envelope-from kib@svn.freebsd.org) Message-Id: <200812191524.mBJFOIMj075547@svn.freebsd.org> From: Konstantin Belousov Date: Fri, 19 Dec 2008 15:24:18 +0000 (UTC) To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-stable@freebsd.org, svn-src-stable-7@freebsd.org X-SVN-Group: stable-7 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Cc: Subject: svn commit: r186324 - in stable/7/sys: . contrib/pf dev/cxgb kern X-BeenThere: svn-src-all@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: "SVN commit messages for the entire src tree \(except for " user" and " projects" \)" List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 19 Dec 2008 15:24:19 -0000 Author: kib Date: Fri Dec 19 15:24:18 2008 New Revision: 186324 URL: http://svn.freebsd.org/changeset/base/186324 Log: MFC r185983: The userland_sysctl() function retries sysctl_root() until returned error is not EAGAIN. Several sysctls that inspect another process use p_candebug() for checking access right for the curproc. p_candebug() returns EAGAIN for some reasons, in particular, for the process doing exec() now. If execing process tries to lock Giant, we get a livelock, because sysctl handlers are covered by Giant, and often do not sleep. Break the livelock by dropping Giant and allowing other threads to execute in the EAGAIN loop. This commit does not merge the following change, as was discussed with jhb: [Also, do not return EAGAIN from p_candebug() when process is executing, use more appropriate EBUSY error.] MFC r185987: Uio_yield() already does DROP_GIANT/PICKUP_GIANT, no need to repeat this around the call. Approved by: re (kensmith) Modified: stable/7/sys/ (props changed) stable/7/sys/contrib/pf/ (props changed) stable/7/sys/dev/cxgb/ (props changed) stable/7/sys/kern/kern_sysctl.c Modified: stable/7/sys/kern/kern_sysctl.c ============================================================================== --- stable/7/sys/kern/kern_sysctl.c Fri Dec 19 15:04:26 2008 (r186323) +++ stable/7/sys/kern/kern_sysctl.c Fri Dec 19 15:24:18 2008 (r186324) @@ -52,6 +52,7 @@ __FBSDID("$FreeBSD$"); #include #include #include +#include #include @@ -1395,11 +1396,14 @@ userland_sysctl(struct thread *td, int * SYSCTL_LOCK(); - do { + for (;;) { req.oldidx = 0; req.newidx = 0; error = sysctl_root(0, name, namelen, &req); - } while (error == EAGAIN); + if (error != EAGAIN) + break; + uio_yield(); + } if (req.lock == REQ_WIRED && req.validlen > 0) vsunlock(req.oldptr, req.validlen);