From patchwork Thu Jun 3 19:59:24 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: =?utf-8?q?Andr=C3=A9_Almeida?= X-Patchwork-Id: 454389 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-16.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI, SPF_HELO_NONE, SPF_PASS, UNPARSEABLE_RELAY, USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 60577C47082 for ; Thu, 3 Jun 2021 20:01:51 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 495F061369 for ; Thu, 3 Jun 2021 20:01:51 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230271AbhFCUDf (ORCPT ); Thu, 3 Jun 2021 16:03:35 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60260 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229894AbhFCUDf (ORCPT ); Thu, 3 Jun 2021 16:03:35 -0400 Received: from bhuna.collabora.co.uk (bhuna.collabora.co.uk [IPv6:2a00:1098:0:82:1000:25:2eeb:e3e3]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id F0F9AC061756; Thu, 3 Jun 2021 13:01:49 -0700 (PDT) Received: from [127.0.0.1] (localhost [127.0.0.1]) (Authenticated sender: tonyk) with ESMTPSA id 6B54A1F434D5 From: =?utf-8?q?Andr=C3=A9_Almeida?= To: Thomas Gleixner , Ingo Molnar , Peter Zijlstra , Darren Hart , linux-kernel@vger.kernel.org, Steven Rostedt , Sebastian Andrzej Siewior Cc: kernel@collabora.com, krisman@collabora.com, pgriffais@valvesoftware.com, z.figura12@gmail.com, joel@joelfernandes.org, malteskarupke@fastmail.fm, linux-api@vger.kernel.org, fweimer@redhat.com, libc-alpha@sourceware.org, linux-kselftest@vger.kernel.org, shuah@kernel.org, acme@kernel.org, corbet@lwn.net, Peter Oskolkov , Andrey Semashev , Davidlohr Bueso , =?utf-8?q?Andr=C3=A9_Almeida?= Subject: [PATCH v4 15/15] kernel: Enable waitpid() for futex2 Date: Thu, 3 Jun 2021 16:59:24 -0300 Message-Id: <20210603195924.361327-16-andrealmeid@collabora.com> X-Mailer: git-send-email 2.31.1 In-Reply-To: <20210603195924.361327-1-andrealmeid@collabora.com> References: <20210603195924.361327-1-andrealmeid@collabora.com> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-kselftest@vger.kernel.org To make pthreads works as expected if they are using futex2, wake clear_child_tid with futex2 as well. This is make applications that uses waitpid() (and clone(CLONE_CHILD_SETTID)) wake while waiting for the child to terminate. Given that apps should not mix futex() and futex2(), any correct app will trigger a harmless noop wakeup on the interface that it isn't using. Signed-off-by: André Almeida --- This commit is here for the intend to show what we need to do in order to get a full NPTL working on top of futex2. It should be merged after we talk to glibc folks on the details around the futex_wait() side. For instance, we could use this as an opportunity to use private futexes or 8bit sized futexes, but both sides need to use the exactly same flags. --- include/linux/syscalls.h | 2 ++ kernel/fork.c | 2 ++ kernel/futex2.c | 30 ++++++++++++++++++------------ 3 files changed, 22 insertions(+), 12 deletions(-) diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h index c108df6b3b82..94e0356ceeaa 100644 --- a/include/linux/syscalls.h +++ b/include/linux/syscalls.h @@ -1324,6 +1324,8 @@ int ksys_ipc(unsigned int call, int first, unsigned long second, unsigned long third, void __user * ptr, long fifth); int compat_ksys_ipc(u32 call, int first, int second, u32 third, u32 ptr, u32 fifth); +long ksys_futex_wake(void __user *uaddr, unsigned long nr_wake, + unsigned int flags); /* * The following kernel syscall equivalents are just wrappers to fs-internal diff --git a/kernel/fork.c b/kernel/fork.c index dc06afd725cb..344430d882b1 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -1322,6 +1322,8 @@ static void mm_release(struct task_struct *tsk, struct mm_struct *mm) put_user(0, tsk->clear_child_tid); do_futex(tsk->clear_child_tid, FUTEX_WAKE, 1, NULL, NULL, 0, 0); + ksys_futex_wake(tsk->clear_child_tid, 1, + FUTEX_32 | FUTEX_SHARED_FLAG); } tsk->clear_child_tid = NULL; } diff --git a/kernel/futex2.c b/kernel/futex2.c index 5fd0b3d73b53..bf2de369b78a 100644 --- a/kernel/futex2.c +++ b/kernel/futex2.c @@ -978,18 +978,8 @@ static inline bool futex_match(struct futex_key key1, struct futex_key key2) key1.offset == key2.offset); } -/** - * sys_futex_wake - Wake a number of futexes waiting on an address - * @uaddr: Address of futex to be woken up - * @nr_wake: Number of futexes waiting in uaddr to be woken up - * @flags: Flags for size and shared - * - * Wake `nr_wake` threads waiting at uaddr. - * - * Returns the number of woken threads on success, error code otherwise. - */ -SYSCALL_DEFINE3(futex_wake, void __user *, uaddr, unsigned int, nr_wake, - unsigned int, flags) +long ksys_futex_wake(void __user *uaddr, unsigned long nr_wake, + unsigned int flags) { bool shared = (flags & FUTEX_SHARED_FLAG) ? true : false; unsigned int size = flags & FUTEX_SIZE_MASK; @@ -1023,6 +1013,22 @@ SYSCALL_DEFINE3(futex_wake, void __user *, uaddr, unsigned int, nr_wake, return ret; } +/** + * sys_futex_wake - Wake a number of futexes waiting on an address + * @uaddr: Address of futex to be woken up + * @nr_wake: Number of futexes waiting in uaddr to be woken up + * @flags: Flags for size and shared + * + * Wake `nr_wake` threads waiting at uaddr. + * + * Returns the number of woken threads on success, error code otherwise. + */ +SYSCALL_DEFINE3(futex_wake, void __user *, uaddr, unsigned int, nr_wake, + unsigned int, flags) +{ + return ksys_futex_wake(uaddr, nr_wake, flags); +} + static void futex_double_unlock(struct futex_bucket *b1, struct futex_bucket *b2) { spin_unlock(&b1->lock);