From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 0671D39FDD; Fri, 24 Nov 2023 18:25:41 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="X2aahakp" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 34C42C433C7; Fri, 24 Nov 2023 18:25:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1700850341; bh=EzUdWxqZwaE+Fu5WrdgFESnq03ugOo/ESfubPY/olaU=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=X2aahakpFds1aMOilCmZu3uUhSiN3lJoBrwin8Cw28o4XbA8H1Z96HCKg772StmVR mpkJVIIfJ/Z4mBrLwChPoGu83N6SjoabXnQfTyflAqKVULWeI92XZ0KbNxvg03NLww 8z4rKIJDvuEHRI47MI8aGwlOn8fXCB7fhf82dzmw= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Yong He , "Joel Fernandes (Google)" , Neeraj upadhyay , Like Xu , Frederic Weisbecker , Sasha Levin Subject: [PATCH 6.5 011/491] srcu: Only accelerate on enqueue time Date: Fri, 24 Nov 2023 17:44:07 +0000 Message-ID: <20231124172025.025412337@linuxfoundation.org> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20231124172024.664207345@linuxfoundation.org> References: <20231124172024.664207345@linuxfoundation.org> User-Agent: quilt/0.67 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.5-stable review patch. If anyone has any objections, please let me know. ------------------ From: Frederic Weisbecker [ Upstream commit 8a77f38bcd28d3c22ab7dd8eff3f299d43c00411 ] Acceleration in SRCU happens on enqueue time for each new callback. This operation is expected not to fail and therefore any similar attempt from other places shouldn't find any remaining callbacks to accelerate. Moreover accelerations performed beyond enqueue time are error prone because rcu_seq_snap() then may return the snapshot for a new grace period that is not going to be started. Remove these dangerous and needless accelerations and introduce instead assertions reporting leaking unaccelerated callbacks beyond enqueue time. Co-developed-by: Yong He Signed-off-by: Yong He Co-developed-by: Joel Fernandes (Google) Signed-off-by: Joel Fernandes (Google) Co-developed-by: Neeraj upadhyay Signed-off-by: Neeraj upadhyay Reviewed-by: Like Xu Signed-off-by: Frederic Weisbecker Signed-off-by: Sasha Levin --- kernel/rcu/srcutree.c | 6 ++---- 1 file changed, 2 insertions(+), 4 deletions(-) diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c index 7522517b63b6f..2f770a9a2a13a 100644 --- a/kernel/rcu/srcutree.c +++ b/kernel/rcu/srcutree.c @@ -782,8 +782,7 @@ static void srcu_gp_start(struct srcu_struct *ssp) spin_lock_rcu_node(sdp); /* Interrupts already disabled. */ rcu_segcblist_advance(&sdp->srcu_cblist, rcu_seq_current(&ssp->srcu_sup->srcu_gp_seq)); - (void)rcu_segcblist_accelerate(&sdp->srcu_cblist, - rcu_seq_snap(&ssp->srcu_sup->srcu_gp_seq)); + WARN_ON_ONCE(!rcu_segcblist_segempty(&sdp->srcu_cblist, RCU_NEXT_TAIL)); spin_unlock_rcu_node(sdp); /* Interrupts remain disabled. */ WRITE_ONCE(ssp->srcu_sup->srcu_gp_start, jiffies); WRITE_ONCE(ssp->srcu_sup->srcu_n_exp_nodelay, 0); @@ -1719,6 +1718,7 @@ static void srcu_invoke_callbacks(struct work_struct *work) ssp = sdp->ssp; rcu_cblist_init(&ready_cbs); spin_lock_irq_rcu_node(sdp); + WARN_ON_ONCE(!rcu_segcblist_segempty(&sdp->srcu_cblist, RCU_NEXT_TAIL)); rcu_segcblist_advance(&sdp->srcu_cblist, rcu_seq_current(&ssp->srcu_sup->srcu_gp_seq)); if (sdp->srcu_cblist_invoking || @@ -1748,8 +1748,6 @@ static void srcu_invoke_callbacks(struct work_struct *work) */ spin_lock_irq_rcu_node(sdp); rcu_segcblist_add_len(&sdp->srcu_cblist, -len); - (void)rcu_segcblist_accelerate(&sdp->srcu_cblist, - rcu_seq_snap(&ssp->srcu_sup->srcu_gp_seq)); sdp->srcu_cblist_invoking = false; more = rcu_segcblist_ready_cbs(&sdp->srcu_cblist); spin_unlock_irq_rcu_node(sdp); -- 2.42.0