From nobody Sun Feb 8 10:32:59 2026 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 58ED1EB64D7 for ; Sun, 18 Jun 2023 20:51:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229818AbjFRUu7 (ORCPT ); Sun, 18 Jun 2023 16:50:59 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:48750 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229648AbjFRUuI (ORCPT ); Sun, 18 Jun 2023 16:50:08 -0400 Received: from galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B57EBE62; Sun, 18 Jun 2023 13:50:07 -0700 (PDT) Date: Sun, 18 Jun 2023 20:50:05 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1687121406; 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=kfFS5YeYIWXVCmFNVUFFakEiFHNW11QHadDZ5vBEsaA=; b=fPkP2hB8XsSI2TnSCicHKo6dSMBpdWoI4DhmiT1npAscCViFJW29PRJi3sGvY9wL1uw2Pd trgqK/ZFlwGBY0CmKMcALtlY6yIJJNYZWTsO1SXOedNiyoSYJ8bA1sG+N6o9klDLL0oJ+B ThhlNr3eAM9UPQKPu0BAwt+twDX7qyEFuqElS8r5nixLrVOAmI1fu9Qpc+ouKNIIWzVKgn VX8+T+IQvwqsVNhCNNdbrQ27PavCXB9T4FwCnqlR8gR+bYWRWF1C6S7/p5ASbTmfksrpkb zHVK9a5ApFc9Ny3VAlrBVVp2JkzGNvtbNGLEuxz7ht7cA08/aw4sCpXZRqvNFA== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1687121406; 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=kfFS5YeYIWXVCmFNVUFFakEiFHNW11QHadDZ5vBEsaA=; b=k9ZhxpG7nd0GHrgQv1MYZ1lonDwlGgRzQLdz6f2JQFe7b2awFqBMtcrEMkQ02oDu55JSJj +mkkUR7W/+xBn4BQ== 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: <168712140583.404.12297488309402742889.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: quoted-printable 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: 028cf5eaa12846c4e32104132ff70ca1cd6f5943 Gitweb: https://git.kernel.org/tip/028cf5eaa12846c4e32104132ff70ca1c= d6f5943 Author: Thomas Gleixner AuthorDate: Tue, 25 Apr 2023 20:49:05 +02:00 Committer: Thomas Gleixner CommitterDate: Sun, 18 Jun 2023 22:41:49 +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 d7890ac..de3fca8 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 hlis= t_head *head, { struct k_itimer *timer; =20 - hlist_for_each_entry_rcu(timer, head, t_hash, - lockdep_is_held(&hash_lock)) { - if ((timer->it_signal =3D=3D sig) && (timer->it_id =3D=3D 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) =3D=3D sig) && (timer->it_id =3D=3D id)) return timer; } return NULL; @@ -558,7 +558,7 @@ static int do_timer_create(clockid_t which_clock, struc= t sigevent *event, =20 spin_lock_irq(¤t->sighand->siglock); /* This makes the timer valid in the hash table */ - new_timer->it_signal =3D 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); =20 @@ -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 =3D NULL; + WRITE_ONCE(timer->it_signal, NULL); =20 unlock_timer(timer, flags); release_posix_timer(timer, IT_ID_SET);