From owner-svn-src-all@FreeBSD.ORG Fri Feb 25 22:03:29 2011 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 21FDC1065670; Fri, 25 Feb 2011 22:03:29 +0000 (UTC) (envelope-from dchagin@FreeBSD.org) Received: from svn.freebsd.org (svn.freebsd.org [IPv6:2001:4f8:fff6::2c]) by mx1.freebsd.org (Postfix) with ESMTP id 05B868FC12; Fri, 25 Feb 2011 22:03:29 +0000 (UTC) Received: from svn.freebsd.org (localhost [127.0.0.1]) by svn.freebsd.org (8.14.3/8.14.3) with ESMTP id p1PM3SKT013729; Fri, 25 Feb 2011 22:03:28 GMT (envelope-from dchagin@svn.freebsd.org) Received: (from dchagin@localhost) by svn.freebsd.org (8.14.3/8.14.3/Submit) id p1PM3SF2013727; Fri, 25 Feb 2011 22:03:28 GMT (envelope-from dchagin@svn.freebsd.org) Message-Id: <201102252203.p1PM3SF2013727@svn.freebsd.org> From: Dmitry Chagin Date: Fri, 25 Feb 2011 22:03:28 +0000 (UTC) To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org X-SVN-Group: head MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Cc: Subject: svn commit: r219041 - head/sys/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, 25 Feb 2011 22:03:29 -0000 Author: dchagin Date: Fri Feb 25 22:03:28 2011 New Revision: 219041 URL: http://svn.freebsd.org/changeset/base/219041 Log: ktrace_resize_pool() locking slightly reworked: 1) do not take a lock around the single atomic operation. 2) do not lose the invariant of lock by dropping/acquiring ktrace_mtx around free() or malloc(). MFC after: 1 Month. Modified: head/sys/kern/kern_ktrace.c Modified: head/sys/kern/kern_ktrace.c ============================================================================== --- head/sys/kern/kern_ktrace.c Fri Feb 25 20:49:07 2011 (r219040) +++ head/sys/kern/kern_ktrace.c Fri Feb 25 22:03:28 2011 (r219041) @@ -133,7 +133,7 @@ static struct sx ktrace_sx; static void ktrace_init(void *dummy); static int sysctl_kern_ktrace_request_pool(SYSCTL_HANDLER_ARGS); -static u_int ktrace_resize_pool(u_int newsize); +static u_int ktrace_resize_pool(u_int oldsize, u_int newsize); static struct ktr_request *ktr_getrequest(int type); static void ktr_submitrequest(struct thread *td, struct ktr_request *req); static void ktr_freeproc(struct proc *p, struct ucred **uc, @@ -199,9 +199,7 @@ sysctl_kern_ktrace_request_pool(SYSCTL_H /* Handle easy read-only case first to avoid warnings from GCC. */ if (!req->newptr) { - mtx_lock(&ktrace_mtx); oldsize = ktr_requestpool; - mtx_unlock(&ktrace_mtx); return (SYSCTL_OUT(req, &oldsize, sizeof(u_int))); } @@ -210,10 +208,8 @@ sysctl_kern_ktrace_request_pool(SYSCTL_H return (error); td = curthread; ktrace_enter(td); - mtx_lock(&ktrace_mtx); oldsize = ktr_requestpool; - newsize = ktrace_resize_pool(wantsize); - mtx_unlock(&ktrace_mtx); + newsize = ktrace_resize_pool(oldsize, wantsize); ktrace_exit(td); error = SYSCTL_OUT(req, &oldsize, sizeof(u_int)); if (error) @@ -227,38 +223,40 @@ SYSCTL_PROC(_kern_ktrace, OID_AUTO, requ "Pool buffer size for ktrace(1)"); static u_int -ktrace_resize_pool(u_int newsize) +ktrace_resize_pool(u_int oldsize, u_int newsize) { + STAILQ_HEAD(, ktr_request) ktr_new; struct ktr_request *req; int bound; - mtx_assert(&ktrace_mtx, MA_OWNED); print_message = 1; - bound = newsize - ktr_requestpool; + bound = newsize - oldsize; if (bound == 0) return (ktr_requestpool); - if (bound < 0) + if (bound < 0) { + mtx_lock(&ktrace_mtx); /* Shrink pool down to newsize if possible. */ while (bound++ < 0) { req = STAILQ_FIRST(&ktr_free); if (req == NULL) - return (ktr_requestpool); + break; STAILQ_REMOVE_HEAD(&ktr_free, ktr_list); ktr_requestpool--; - mtx_unlock(&ktrace_mtx); free(req, M_KTRACE); - mtx_lock(&ktrace_mtx); } - else + } else { /* Grow pool up to newsize. */ + STAILQ_INIT(&ktr_new); while (bound-- > 0) { - mtx_unlock(&ktrace_mtx); req = malloc(sizeof(struct ktr_request), M_KTRACE, M_WAITOK); - mtx_lock(&ktrace_mtx); - STAILQ_INSERT_HEAD(&ktr_free, req, ktr_list); - ktr_requestpool++; + STAILQ_INSERT_HEAD(&ktr_new, req, ktr_list); } + mtx_lock(&ktrace_mtx); + STAILQ_CONCAT(&ktr_free, &ktr_new); + ktr_requestpool += (newsize - oldsize); + } + mtx_unlock(&ktrace_mtx); return (ktr_requestpool); }