From owner-dev-commits-src-main@freebsd.org Wed Jun 23 21:36:42 2021 Return-Path: Delivered-To: dev-commits-src-main@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 DDD14658888; Wed, 23 Jun 2021 21:36:42 +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 4G9Gmp5jPYz4VHy; Wed, 23 Jun 2021 21:36:42 +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 8EE6137E4; Wed, 23 Jun 2021 21:36:42 +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 15NLagCV077102; Wed, 23 Jun 2021 21:36:42 GMT (envelope-from git@gitrepo.freebsd.org) Received: (from git@localhost) by gitrepo.freebsd.org (8.16.1/8.16.1/Submit) id 15NLag2E077101; Wed, 23 Jun 2021 21:36:42 GMT (envelope-from git) Date: Wed, 23 Jun 2021 21:36:42 GMT Message-Id: <202106232136.15NLag2E077101@gitrepo.freebsd.org> To: src-committers@FreeBSD.org, dev-commits-src-all@FreeBSD.org, dev-commits-src-main@FreeBSD.org From: Konstantin Belousov Subject: git: 60b0ad10dd0f - main - vdso: lower precision of vdso implementation of CLOCK_MONOTONIC_FAST and CLOCK_UPTIME_FAST MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit X-Git-Committer: kib X-Git-Repository: src X-Git-Refname: refs/heads/main X-Git-Reftype: branch X-Git-Commit: 60b0ad10dd0fc7ff6892ecc7ba3458482fcc064c Auto-Submitted: auto-generated X-BeenThere: dev-commits-src-main@freebsd.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: Commit messages for the main branch of the src repository List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 23 Jun 2021 21:36:43 -0000 The branch main has been updated by kib: URL: https://cgit.FreeBSD.org/src/commit/?id=60b0ad10dd0fc7ff6892ecc7ba3458482fcc064c commit 60b0ad10dd0fc7ff6892ecc7ba3458482fcc064c Author: Konstantin Belousov AuthorDate: 2021-06-22 23:24:08 +0000 Commit: Konstantin Belousov CommitDate: 2021-06-23 21:36:33 +0000 vdso: lower precision of vdso implementation of CLOCK_MONOTONIC_FAST and CLOCK_UPTIME_FAST so that libc vdso and kernel syscall give closer results. Reported by: dchagin Reviewed by: markj Sponsored by: The FreeBSD Foundation MFC after: 1 week Differential revision: https://reviews.freebsd.org/D30873 --- lib/libc/sys/__vdso_gettimeofday.c | 28 +++++++++++++++++++++++++++- 1 file changed, 27 insertions(+), 1 deletion(-) diff --git a/lib/libc/sys/__vdso_gettimeofday.c b/lib/libc/sys/__vdso_gettimeofday.c index 4c1f4bda23e1..c1457a54d37e 100644 --- a/lib/libc/sys/__vdso_gettimeofday.c +++ b/lib/libc/sys/__vdso_gettimeofday.c @@ -106,6 +106,30 @@ binuptime(struct bintime *bt, struct vdso_timekeep *tk, bool abs) return (0); } +static int +getnanouptime(struct bintime *bt, struct vdso_timekeep *tk) +{ + struct vdso_timehands *th; + uint32_t curr, gen; + + do { + if (!tk->tk_enabled) + return (ENOSYS); + + curr = atomic_load_acq_32(&tk->tk_current); + th = &tk->tk_th[curr]; + gen = atomic_load_acq_32(&th->th_gen); + *bt = th->th_offset; + + /* + * Ensure that the load of th_offset is completed + * before the load of th_gen. + */ + atomic_thread_fence_acq(); + } while (curr != tk->tk_current || gen == 0 || gen != th->th_gen); + return (0); +} + static struct vdso_timekeep *tk; #pragma weak __vdso_gettimeofday @@ -154,9 +178,11 @@ __vdso_clock_gettime(clockid_t clock_id, struct timespec *ts) break; case CLOCK_MONOTONIC: case CLOCK_MONOTONIC_PRECISE: - case CLOCK_MONOTONIC_FAST: case CLOCK_UPTIME: case CLOCK_UPTIME_PRECISE: + error = binuptime(&bt, tk, false); + break; + case CLOCK_MONOTONIC_FAST: case CLOCK_UPTIME_FAST: error = getnanouptime(&bt, tk); break;