From owner-dev-commits-src-all@freebsd.org Thu Aug 19 01:12:02 2021 Return-Path: Delivered-To: dev-commits-src-all@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 76CA765A152; Thu, 19 Aug 2021 01:12:02 +0000 (UTC) (envelope-from git@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 "R3" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id 4GqmvQ2nNHz3pjl; Thu, 19 Aug 2021 01:12:02 +0000 (UTC) (envelope-from git@FreeBSD.org) Received: from gitrepo.freebsd.org (gitrepo.freebsd.org [IPv6:2610:1c1:1:6068::e6a:5]) (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 did not present a certificate) by mxrelay.nyi.freebsd.org (Postfix) with ESMTPS id 47C661BF00; Thu, 19 Aug 2021 01:12:02 +0000 (UTC) (envelope-from git@FreeBSD.org) Received: from gitrepo.freebsd.org ([127.0.1.44]) by gitrepo.freebsd.org (8.16.1/8.16.1) with ESMTP id 17J1C2DS017435; Thu, 19 Aug 2021 01:12:02 GMT (envelope-from git@gitrepo.freebsd.org) Received: (from git@localhost) by gitrepo.freebsd.org (8.16.1/8.16.1/Submit) id 17J1C2Ea017434; Thu, 19 Aug 2021 01:12:02 GMT (envelope-from git) Date: Thu, 19 Aug 2021 01:12:02 GMT Message-Id: <202108190112.17J1C2Ea017434@gitrepo.freebsd.org> To: src-committers@FreeBSD.org, dev-commits-src-all@FreeBSD.org, dev-commits-src-branches@FreeBSD.org From: Alexander Motin Subject: git: 09d4fe40e039 - stable/13 - Fix race between first rand(3) calls with _once(). MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit X-Git-Committer: mav X-Git-Repository: src X-Git-Refname: refs/heads/stable/13 X-Git-Reftype: branch X-Git-Commit: 09d4fe40e039d4b08a034454c36aed86571725b0 Auto-Submitted: auto-generated X-BeenThere: dev-commits-src-all@freebsd.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: Commit messages for all branches of the src repository List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 19 Aug 2021 01:12:02 -0000 The branch stable/13 has been updated by mav: URL: https://cgit.FreeBSD.org/src/commit/?id=09d4fe40e039d4b08a034454c36aed86571725b0 commit 09d4fe40e039d4b08a034454c36aed86571725b0 Author: Alexander Motin AuthorDate: 2021-07-21 15:25:46 +0000 Commit: Alexander Motin CommitDate: 2021-08-19 01:11:51 +0000 Fix race between first rand(3) calls with _once(). Before this patch there was a chance for thread that called rand(3) slightly later to see rand3_state already allocated, but not yet initialized. While this API is not expected to be thread-safe, it is not expected to crash. ztest on 64-thread system reproduced it reliably for me. Submitted by: avg@ MFC after: 1 month (cherry picked from commit 3a57f08b5042f15bb8ffb2fcce99d082d225d4cf) --- lib/libc/stdlib/rand.c | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-) diff --git a/lib/libc/stdlib/rand.c b/lib/libc/stdlib/rand.c index bddb0f040302..e448d1b1fd14 100644 --- a/lib/libc/stdlib/rand.c +++ b/lib/libc/stdlib/rand.c @@ -41,11 +41,13 @@ __FBSDID("$FreeBSD$"); #include #include #include +#include #include #include #include #include "un-namespace.h" +#include "libc_private.h" #include "random.h" /* @@ -64,6 +66,7 @@ __FBSDID("$FreeBSD$"); * the advantage of being the one already in the tree. */ static struct __random_state *rand3_state; +static pthread_once_t rand3_state_once = PTHREAD_ONCE_INIT; static void initialize_rand3(void) @@ -78,16 +81,14 @@ initialize_rand3(void) int rand(void) { - if (rand3_state == NULL) - initialize_rand3(); + _once(&rand3_state_once, initialize_rand3); return ((int)random_r(rand3_state)); } void srand(unsigned seed) { - if (rand3_state == NULL) - initialize_rand3(); + _once(&rand3_state_once, initialize_rand3); srandom_r(rand3_state, seed); }