From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 4F41AC7EE24 for ; Mon, 5 Jun 2023 15:09:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234731AbjFEPJL (ORCPT ); Mon, 5 Jun 2023 11:09:11 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47988 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234179AbjFEPId (ORCPT ); Mon, 5 Jun 2023 11:08:33 -0400 Received: from galois.linutronix.de (Galois.linutronix.de [193.142.43.55]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 6920BF3; Mon, 5 Jun 2023 08:08:32 -0700 (PDT) Date: Mon, 05 Jun 2023 15:08:30 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1685977711; h=from:from:sender:sender:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=qQgeEb9hS2OwslC7UYMEj5kd+JcImTvjidFJIvXXFOs=; b=jS1DOadp3IhmJDNaG14EhTQmT1+W7/QTKKTf9jWhDcFOqUERAJOz6qQj+meKSGzKlL15jM cLWMmwISBltGwbP0QllEHbHoMtBtD6DqNZ6lARHu6AOu3vTfR342xmkdoXT9C4MWMREe3m 7ZjeN3+HnKrEC8yzPhEnCKhicuRy7n6KkF3cJtvJ9sD5uioDjoZxOYAbYxX3QEPL37MBX8 +VaKVyPRDTGm17Tm1oRj75Xjqd3uyUM8/Pwi1hpCH4RX6s9iXtHiFPt+Y5XWzLW0cksVax yu68vNV4/innosGKBKwrQLooQsmKRwbtE88VfIaSIPZCd0SfF8kn9PIm7nBaTA== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1685977711; h=from:from:sender:sender:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=qQgeEb9hS2OwslC7UYMEj5kd+JcImTvjidFJIvXXFOs=; b=U1LBd8ErHQ6NvkVNFsv3pPQjmXOlBLNmWR2jKXS3khWdYoR0/qA3uL+HUsNIFtpA67Bc/6 2loI/UUxOhuYq0CQ== From: "tip-bot2 for Thomas Gleixner" Sender: tip-bot2@linutronix.de Reply-to: linux-kernel@vger.kernel.org To: linux-tip-commits@vger.kernel.org Subject: [tip: timers/core] posix-timers: Annotate concurrent access to k_itimer:: It_signal Cc: Thomas Gleixner , Frederic Weisbecker , x86@kernel.org, linux-kernel@vger.kernel.org In-Reply-To: <20230425183313.143596887@linutronix.de> References: <20230425183313.143596887@linutronix.de> MIME-Version: 1.0 Message-ID: <168597771061.404.17723098484982029633.tip-bot2@tip-bot2> Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The following commit has been merged into the timers/core branch of tip: Commit-ID: d69e873ee50459e3b77019263cf95236f063a97b Gitweb: https://git.kernel.org/tip/d69e873ee50459e3b77019263cf95236f063a97b Author: Thomas Gleixner AuthorDate: Tue, 25 Apr 2023 20:49:05 +02:00 Committer: Thomas Gleixner CommitterDate: Mon, 05 Jun 2023 17:03:37 +02:00 posix-timers: Annotate concurrent access to k_itimer:: It_signal k_itimer::it_signal is read lockless in the RCU protected hash lookup, but it can be written concurrently in the timer_create() and timer_delete() path. Annotate these places with READ_ONCE() and WRITE_ONCE() Signed-off-by: Thomas Gleixner Reviewed-by: Frederic Weisbecker Link: https://lore.kernel.org/r/20230425183313.143596887@linutronix.de --- kernel/time/posix-timers.c | 14 +++++++------- 1 file changed, 7 insertions(+), 7 deletions(-) diff --git a/kernel/time/posix-timers.c b/kernel/time/posix-timers.c index f6650c1..4333334 100644 --- a/kernel/time/posix-timers.c +++ b/kernel/time/posix-timers.c @@ -109,9 +109,9 @@ static struct k_itimer *__posix_timers_find(struct hlist_head *head, { struct k_itimer *timer; - hlist_for_each_entry_rcu(timer, head, t_hash, - lockdep_is_held(&hash_lock)) { - if ((timer->it_signal == sig) && (timer->it_id == id)) + hlist_for_each_entry_rcu(timer, head, t_hash, lockdep_is_held(&hash_lock)) { + /* timer->it_signal can be set concurrently */ + if ((READ_ONCE(timer->it_signal) == sig) && (timer->it_id == id)) return timer; } return NULL; @@ -558,7 +558,7 @@ static int do_timer_create(clockid_t which_clock, struct sigevent *event, spin_lock_irq(¤t->sighand->siglock); /* This makes the timer valid in the hash table */ - new_timer->it_signal = current->signal; + WRITE_ONCE(new_timer->it_signal, current->signal); list_add(&new_timer->list, ¤t->signal->posix_timers); spin_unlock_irq(¤t->sighand->siglock); @@ -1052,10 +1052,10 @@ retry_delete: list_del(&timer->list); spin_unlock(¤t->sighand->siglock); /* - * This keeps any tasks waiting on the spin lock from thinking - * they got something (see the lock code above). + * A concurrent lookup could check timer::it_signal lockless. It + * will reevaluate with timer::it_lock held and observe the NULL. */ - timer->it_signal = NULL; + WRITE_ONCE(timer->it_signal, NULL); unlock_timer(timer, flags); release_posix_timer(timer, IT_ID_SET);