From patchwork Mon Feb 15 15:24:04 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: 42061 Return-Path: X-Original-To: patchwork@sourceware.org Delivered-To: patchwork@sourceware.org Received: from server2.sourceware.org (localhost [IPv6:::1]) by sourceware.org (Postfix) with ESMTP id 888CB395BC4F; Mon, 15 Feb 2021 15:25:47 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 888CB395BC4F DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=sourceware.org; s=default; t=1613402747; bh=2yAPK8SLuDCv+eRwtwwu784DYy5IkA8iMST+CzN+I0U=; h=To:Subject:Date:In-Reply-To:References:List-Id:List-Unsubscribe: List-Archive:List-Post:List-Help:List-Subscribe:From:Reply-To:Cc: From; b=Z8zltXZ426ybhK6An9umtWw3oPXftlSFLn3AdSZAmZOdBc2baMM/4DnOH281LB9ZJ CnYbw08AhHYTVHbwwI+HUD+PDi5o1d1htzb0lK3vj1Czhtdm36YaUr2nr0j28ymT/g HazeiSypMVjngZwUeJXwLpHGjLRp3Emg7mHGLkC0= X-Original-To: libc-alpha@sourceware.org Delivered-To: libc-alpha@sourceware.org Received: from bhuna.collabora.co.uk (bhuna.collabora.co.uk [IPv6:2a00:1098:0:82:1000:25:2eeb:e3e3]) by sourceware.org (Postfix) with ESMTPS id B1A4A395C079 for ; Mon, 15 Feb 2021 15:25:44 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.3.2 sourceware.org B1A4A395C079 Received: from [127.0.0.1] (localhost [127.0.0.1]) (Authenticated sender: tonyk) with ESMTPSA id 23AB81F44F31 To: Thomas Gleixner , Ingo Molnar , Peter Zijlstra , Darren Hart , linux-kernel@vger.kernel.org, Steven Rostedt , Sebastian Andrzej Siewior Subject: [RFC PATCH 13/13] kernel: Enable waitpid() for futex2 Date: Mon, 15 Feb 2021 12:24:04 -0300 Message-Id: <20210215152404.250281-14-andrealmeid@collabora.com> X-Mailer: git-send-email 2.30.1 In-Reply-To: <20210215152404.250281-1-andrealmeid@collabora.com> References: <20210215152404.250281-1-andrealmeid@collabora.com> MIME-Version: 1.0 X-Spam-Status: No, score=-11.6 required=5.0 tests=BAYES_00, GIT_PATCH_0, KAM_DMARC_STATUS, KAM_MANYTO, KAM_NUMSUBJECT, SPF_HELO_PASS, SPF_PASS, TXREP, UNPARSEABLE_RELAY autolearn=ham autolearn_force=no version=3.4.2 X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on server2.sourceware.org X-BeenThere: libc-alpha@sourceware.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Libc-alpha mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-Patchwork-Original-From: =?utf-8?q?Andr=C3=A9_Almeida_via_Libc-alpha?= From: =?utf-8?q?Andr=C3=A9_Almeida?= Reply-To: =?utf-8?q?Andr=C3=A9_Almeida?= Cc: fweimer@redhat.com, shuah@kernel.org, libc-alpha@sourceware.org, corbet@lwn.net, linux-api@vger.kernel.org, z.figura12@gmail.com, malteskarupke@fastmail.fm, acme@kernel.org, linux-kselftest@vger.kernel.org, =?utf-8?q?Andr=C3=A9_Almeida?= , joel@joelfernandes.org, kernel@collabora.com, krisman@collabora.com, pgriffais@valvesoftware.com Errors-To: libc-alpha-bounces@sourceware.org Sender: "Libc-alpha" 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 06823bc7ef9d..38c2fc50ada9 100644 --- a/include/linux/syscalls.h +++ b/include/linux/syscalls.h @@ -1312,6 +1312,8 @@ 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 d66cd1014211..e39846a73a43 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -1308,6 +1308,8 @@ 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 8a8b45f98d3b..a810b7f5c3a0 100644 --- a/kernel/futex2.c +++ b/kernel/futex2.c @@ -942,18 +942,8 @@ 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; @@ -990,6 +980,22 @@ 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);