From patchwork Thu Mar 28 17:19:46 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Leonardo Bras Soares Passos X-Patchwork-Id: 13609248 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) (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 CF79E80BF0 for ; Thu, 28 Mar 2024 17:20:06 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.129.124 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1711646408; cv=none; b=HYebumdsAbBO4KODVwCdoBTCKZSpSvl6OI1v3KWmpeSCLR6oJJnyKw0ATf9hD5sns9W+3lj/8Z7qr3ZJSl1H5164mCQDl3jknwOInWhLQoYPMwYicq/Nti+kALV0PLNn1vrJcInezrzutDtpy7xyb7cdefcwVkXNdwn9DoGYCVo= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1711646408; c=relaxed/simple; bh=5nG12px40b95OiupwSpL661ZIzoB74o9DKh2Yxu7VGA=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=HqTEieWWNDM/cI9ZptCZYtJD9wJQzSfvUfTkMpf8etkbrHwq6UDQHe5M8hs227GAn63gZCYoEaopY9O2lx3iWs1NY0V9QJueYNolSVrM9/Z/bWwn+M1faHcmeiApyU1qRNih0QrIZUTd4jF0TzTY3lqo8U9BTNFdqrUjZqCfeLU= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=PWMuD8rk; arc=none smtp.client-ip=170.10.129.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="PWMuD8rk" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1711646406; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=NlDC3S558v4nqZXrURYnNQqnqNZ8k/Xoba+HwgD1low=; b=PWMuD8rkq8W/Byu8Uyyu4wMXEuNv71muovk5EwbD9ZKrPm8DAQaNwr41FWCoNd4R+RH0p3 g/fMV5P8sgrfWD1hbe4Sd/8Q8AOTWuNwTXjJqTUdnCOu1nLjcxRkY+uz7ExpeOirlb9RNT wBx/VisB7k9PWgAV+zc/2otZE7/wb1k= Received: from mail-qv1-f69.google.com (mail-qv1-f69.google.com [209.85.219.69]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-251-rDgbDAV-MmOnEezqVLOvyQ-1; Thu, 28 Mar 2024 13:20:04 -0400 X-MC-Unique: rDgbDAV-MmOnEezqVLOvyQ-1 Received: by mail-qv1-f69.google.com with SMTP id 6a1803df08f44-69680a9fe29so9890226d6.1 for ; Thu, 28 Mar 2024 10:20:04 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1711646404; x=1712251204; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=NlDC3S558v4nqZXrURYnNQqnqNZ8k/Xoba+HwgD1low=; b=MfUq5DpsC01NYGvh99wSYedUVgicOxsESifR4m5+DCFoJaj9ww9iUDKErnr1OgSB6H q33XyLHyOicLCA2AjMy8YS1NePXZmehp7BroD0Rdwn+UawX7nIEteuu8JYOzAjtzajh2 n8HmXqnMkicJnr3/R5i7Fvxe6ze7ywIMoxfLMBZ2JZ2llUvRCOri0zI5GHwopme8wcay ora72sEB3S1/FyvdQ10A1ae1k7sW8cIsyknyhTc5EsqbbEd2O4sLu8DKpmiKcq6nK495 vKvZozIwzPDn3P1wkOGuE6ECLCqy9JJBJhvB1yxTNgibZ2wCOb5sGn04F7sBfRekDNOK bVSQ== X-Forwarded-Encrypted: i=1; AJvYcCXjWFYcd8bVLgKN15kNCtjjSWYnBE4mQnLtBtCqyqOTlgw3I3VUmWn/y6YifmcjY/HLMaUG3kZc7JkoqowBigvbfoV/ X-Gm-Message-State: AOJu0Yx9jxx1UXLAfUO6jupdvAuwrDn3zFm26n8/ZswveKM4rMf28XqY OJU/TsntCiQf/QBftpgicbaOT0YU93F/URWghrfLIBJojSEsxEKKtZroHjHvTWKiJaQaNLqBBNY eOSHt5v/NEt3U/BISvWgFZl//h+a2Fgm0+7QEr0bTJnXYyo0QJw== X-Received: by 2002:a05:6214:500a:b0:698:7ab0:eb15 with SMTP id jo10-20020a056214500a00b006987ab0eb15mr2054237qvb.46.1711646403994; Thu, 28 Mar 2024 10:20:03 -0700 (PDT) X-Google-Smtp-Source: AGHT+IFmeHJjJWBC27/ap5AWRtSmt7CBRCbfvjktUlnWlqC/t2lVabfEtbBhByfRUEWDgZkb7PIurw== X-Received: by 2002:a05:6214:500a:b0:698:7ab0:eb15 with SMTP id jo10-20020a056214500a00b006987ab0eb15mr2054204qvb.46.1711646403682; Thu, 28 Mar 2024 10:20:03 -0700 (PDT) Received: from LeoBras.redhat.com ([2804:1b3:a801:d7ed:4b57:3fcd:d5e6:a613]) by smtp.gmail.com with ESMTPSA id m13-20020ad45dcd000000b00696944e3ce6sm809078qvh.74.2024.03.28.10.20.00 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 28 Mar 2024 10:20:03 -0700 (PDT) From: Leonardo Bras To: Paolo Bonzini , "Paul E. McKenney" , Frederic Weisbecker , Neeraj Upadhyay , Joel Fernandes , Josh Triplett , Boqun Feng , Steven Rostedt , Mathieu Desnoyers , Lai Jiangshan , Zqiang , Marcelo Tosatti Cc: Leonardo Bras , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, rcu@vger.kernel.org Subject: [RFC PATCH v1 1/2] kvm: Implement guest_exit_last_time() Date: Thu, 28 Mar 2024 14:19:46 -0300 Message-ID: <20240328171949.743211-2-leobras@redhat.com> X-Mailer: git-send-email 2.44.0 In-Reply-To: <20240328171949.743211-1-leobras@redhat.com> References: <20240328171949.743211-1-leobras@redhat.com> Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Keep track of the last time a cpu ran guest_exit(), and provide a helper to make this information available to other files. Signed-off-by: Leonardo Bras --- include/linux/kvm_host.h | 13 +++++++++++++ virt/kvm/kvm_main.c | 3 +++ 2 files changed, 16 insertions(+) diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h index 48f31dcd318a..be90d83d631a 100644 --- a/include/linux/kvm_host.h +++ b/include/linux/kvm_host.h @@ -470,31 +470,44 @@ static __always_inline void guest_state_enter_irqoff(void) { instrumentation_begin(); trace_hardirqs_on_prepare(); lockdep_hardirqs_on_prepare(); instrumentation_end(); guest_context_enter_irqoff(); lockdep_hardirqs_on(CALLER_ADDR0); } +DECLARE_PER_CPU(unsigned long, kvm_last_guest_exit); + +/* + * Returns time (jiffies) for the last guest exit in current cpu + */ +static inline unsigned long guest_exit_last_time(void) +{ + return this_cpu_read(kvm_last_guest_exit); +} + /* * Exit guest context and exit an RCU extended quiescent state. * * Between guest_context_enter_irqoff() and guest_context_exit_irqoff() it is * unsafe to use any code which may directly or indirectly use RCU, tracing * (including IRQ flag tracing), or lockdep. All code in this period must be * non-instrumentable. */ static __always_inline void guest_context_exit_irqoff(void) { context_tracking_guest_exit(); + + /* Keeps track of last guest exit */ + this_cpu_write(kvm_last_guest_exit, jiffies); } /* * Stop accounting time towards a guest. * Must be called after exiting guest context. */ static __always_inline void guest_timing_exit_irqoff(void) { instrumentation_begin(); /* Flush the guest cputime we spent on the guest */ diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index fb49c2a60200..732b1ab43ac9 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -103,20 +103,23 @@ EXPORT_SYMBOL_GPL(halt_poll_ns_shrink); */ DEFINE_MUTEX(kvm_lock); LIST_HEAD(vm_list); static struct kmem_cache *kvm_vcpu_cache; static __read_mostly struct preempt_ops kvm_preempt_ops; static DEFINE_PER_CPU(struct kvm_vcpu *, kvm_running_vcpu); +DEFINE_PER_CPU(unsigned long, kvm_last_guest_exit); +EXPORT_SYMBOL_GPL(kvm_last_guest_exit); + struct dentry *kvm_debugfs_dir; EXPORT_SYMBOL_GPL(kvm_debugfs_dir); static const struct file_operations stat_fops_per_vm; static long kvm_vcpu_ioctl(struct file *file, unsigned int ioctl, unsigned long arg); #ifdef CONFIG_KVM_COMPAT static long kvm_vcpu_compat_ioctl(struct file *file, unsigned int ioctl, unsigned long arg); From patchwork Thu Mar 28 17:19:47 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Leonardo Bras Soares Passos X-Patchwork-Id: 13609249 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) (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 0484512EBF3 for ; Thu, 28 Mar 2024 17:20:09 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.133.124 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1711646411; cv=none; b=GuKpvSOkACKbgcXqP61iHTdXhbFy41b9cP4v/dZTp75F1wQU5+znabz2e1NpZrvNGV4y/DcUPXTPDtsNxSnfxY3QmEaipjtl2UlYazi3o7VmwHZOUb8+fLW5AmjrGIDu+826aO/NZVZfp7iUbgKUKybYOvGlGHm/VyhmbINjWM8= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1711646411; c=relaxed/simple; bh=9y2U5zj1XSiEZQqP81LBCuKEobrFxtST9vwkP9GvsHo=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=IfeQv7csLdFjGlXw7fd6CSZC49hxps1nf7jG3BEPIA9yi2tXq3wl1R8RTZr7SUe5ojoygqtm1/hAcWgYC5NH1hvvTVZkURamyni2bOHvtVPpD44baWWkCX4/pkdfAaUf+GShmuhqIGLMV8Yg1Bz85j2+w+ABdqnsMMaAe3TWlF4= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=iW/39pDo; arc=none smtp.client-ip=170.10.133.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="iW/39pDo" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1711646409; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=pOGUZjzjTM5VUWa9Ov+ku8ROX6G2+xVfPm/xO/kgd3w=; b=iW/39pDoI8497qY2VcIMIOvSyNge0Yu6AQLaksdnsrGyPGf7G8Y1qcaR+ff6BpNHmqFh0V SzV1uJByhxScDX44bWzlv6lclEAn12PR0YATZiXo6oSqrNk+jtRIX2LK0TRMwbFMrtXQQw E+kQ6IpnIkBBZdaOrTJGExafhd3EfVg= Received: from mail-oi1-f199.google.com (mail-oi1-f199.google.com [209.85.167.199]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-164-pxKe6mopN92iU6MKvaH-1w-1; Thu, 28 Mar 2024 13:20:07 -0400 X-MC-Unique: pxKe6mopN92iU6MKvaH-1w-1 Received: by mail-oi1-f199.google.com with SMTP id 5614622812f47-3c3cd9d1741so790788b6e.0 for ; Thu, 28 Mar 2024 10:20:07 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1711646407; x=1712251207; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=pOGUZjzjTM5VUWa9Ov+ku8ROX6G2+xVfPm/xO/kgd3w=; b=Y56qmHnZpLdL4CMCv2zBuPgoMfRX5z8clfiMYOncblUyVEShe1mI97Orbcg3o858Lp i8ToqxgFW1tS4XyAXwa0C0B8dkXeOzO0L65edoN4hiwybN1TAUDvdHNbs6aQ0aH7Ze7c VuD7hBmxpCanZu2DsJjPtqdhOIUJX5gXDQKFcZMNBy2iStOtBb2shJyZGP6BraYv49Aj yiRrdDjoAkMYfC1nKHyoBU6z5SAxf3x6sUCmSVnhOWZgNmik6bYL9AmdbH//pHs9Heux q+a+xvWi1f1SRbgok605WKbNzWsoSD7UcE/7/LZZFe3Vhpoh2AQudEbkPPkQHLNyJhyv AQwA== X-Forwarded-Encrypted: i=1; AJvYcCU0pMaT/9ouQc+BxQgnjNJH9aFfvMtMBf9SImnjt5bEay062ilK8GYs9R8c7xvUvKaF85Cq0H7VGKRjgJg0wkf9V6Am X-Gm-Message-State: AOJu0YwAydXXZA+9tJAlkWGf6HWBEI+TTOk+UC98cQnseHnUxKsOgjmz jpC3ILZjMwSFuWS/RxWeNCF9tzRNjEltxwYhr/tQgw84AyaLYLHab9T6e1fTWW/JDpmNR2Xv1tv iFr2SAlv87YfONj/DENNFxT9AhansB5Di9eVm1LPuHV1Z9OZAfQ== X-Received: by 2002:a05:6808:1242:b0:3c3:dfec:d9ee with SMTP id o2-20020a056808124200b003c3dfecd9eemr3965567oiv.32.1711646406952; Thu, 28 Mar 2024 10:20:06 -0700 (PDT) X-Google-Smtp-Source: AGHT+IHu853ijuqNBx1nyDj4vEt9gDt5cv976tFHHSJ9WoGLzNibEXGLlQqgvCaSZT7OfU274ydjLg== X-Received: by 2002:a05:6808:1242:b0:3c3:dfec:d9ee with SMTP id o2-20020a056808124200b003c3dfecd9eemr3965545oiv.32.1711646406669; Thu, 28 Mar 2024 10:20:06 -0700 (PDT) Received: from LeoBras.redhat.com ([2804:1b3:a801:d7ed:4b57:3fcd:d5e6:a613]) by smtp.gmail.com with ESMTPSA id m13-20020ad45dcd000000b00696944e3ce6sm809078qvh.74.2024.03.28.10.20.03 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 28 Mar 2024 10:20:06 -0700 (PDT) From: Leonardo Bras To: Paolo Bonzini , "Paul E. McKenney" , Frederic Weisbecker , Neeraj Upadhyay , Joel Fernandes , Josh Triplett , Boqun Feng , Steven Rostedt , Mathieu Desnoyers , Lai Jiangshan , Zqiang , Marcelo Tosatti Cc: Leonardo Bras , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, rcu@vger.kernel.org Subject: [RFC PATCH v1 2/2] rcu: Ignore RCU in nohz_full cpus if it was running a guest recently Date: Thu, 28 Mar 2024 14:19:47 -0300 Message-ID: <20240328171949.743211-3-leobras@redhat.com> X-Mailer: git-send-email 2.44.0 In-Reply-To: <20240328171949.743211-1-leobras@redhat.com> References: <20240328171949.743211-1-leobras@redhat.com> Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 In current code, we can ignore the RCU request on a nohz_full cpu for up to a second if it has interrupted idle or userspace tasks, since those are quiescent states, and will probably return to it soon thus not requiring to run a softirq or a rcuc thread. Running a guest is also considered to be a quiescent state, and will follow the same logic, so it makes sense to also ignore the RCU request in this case. This solves a latency issue of a latency-sensitive workload running on a guest pinned in nohz_full cpu: if the guest goes out for any reason, and a synchronize_rcu() is requested between guest exit and a timer interrupt, then invoke_rcu_core() is called, and introduce latency due to either a softirq, or a reschedule to run rcuc, if the host is a PREEMPT_RT kernel. Suggested-by: Marcelo Tosatti Signed-off-by: Leonardo Bras Acked-by: Paul E. McKenney --- kernel/rcu/tree_plugin.h | 14 ++++++++++++++ kernel/rcu/tree.c | 4 +++- 2 files changed, 17 insertions(+), 1 deletion(-) diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h index 36a8b5dbf5b5..16f3cf2e15df 100644 --- a/kernel/rcu/tree_plugin.h +++ b/kernel/rcu/tree_plugin.h @@ -5,20 +5,21 @@ * or preemptible semantics. * * Copyright Red Hat, 2009 * Copyright IBM Corporation, 2009 * * Author: Ingo Molnar * Paul E. McKenney */ #include "../locking/rtmutex_common.h" +#include "linux/kvm_host.h" static bool rcu_rdp_is_offloaded(struct rcu_data *rdp) { /* * In order to read the offloaded state of an rdp in a safe * and stable way and prevent from its value to be changed * under us, we must either hold the barrier mutex, the cpu * hotplug lock (read or write) or the nocb lock. Local * non-preemptible reads are also safe. NOCB kthreads and * timers have their own means of synchronization against the @@ -1260,10 +1261,23 @@ static bool rcu_nohz_full_cpu(void) /* * Bind the RCU grace-period kthreads to the housekeeping CPU. */ static void rcu_bind_gp_kthread(void) { if (!tick_nohz_full_enabled()) return; housekeeping_affine(current, HK_TYPE_RCU); } + +/* + * true if for this cpu guest exit is at most over a second ago, + * false otherwise + */ +static bool rcu_recent_guest_exit(void) +{ +#ifdef CONFIG_KVM + return time_before(jiffies, guest_exit_last_time() + HZ); +#else + return false; +#endif +} diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index d9642dd06c25..e5ce00bf1898 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -148,20 +148,21 @@ static void rcu_report_qs_rnp(unsigned long mask, struct rcu_node *rnp, static struct task_struct *rcu_boost_task(struct rcu_node *rnp); static void invoke_rcu_core(void); static void rcu_report_exp_rdp(struct rcu_data *rdp); static void sync_sched_exp_online_cleanup(int cpu); static void check_cb_ovld_locked(struct rcu_data *rdp, struct rcu_node *rnp); static bool rcu_rdp_is_offloaded(struct rcu_data *rdp); static bool rcu_rdp_cpu_online(struct rcu_data *rdp); static bool rcu_init_invoked(void); static void rcu_cleanup_dead_rnp(struct rcu_node *rnp_leaf); static void rcu_init_new_rnp(struct rcu_node *rnp_leaf); +static bool rcu_recent_guest_exit(void); /* * rcuc/rcub/rcuop kthread realtime priority. The "rcuop" * real-time priority(enabling/disabling) is controlled by * the extra CONFIG_RCU_NOCB_CPU_CB_BOOST configuration. */ static int kthread_prio = IS_ENABLED(CONFIG_RCU_BOOST) ? 1 : 0; module_param(kthread_prio, int, 0444); /* Delay in jiffies for grace-period initialization delays, debug only. */ @@ -3931,21 +3932,22 @@ static int rcu_pending(int user) lockdep_assert_irqs_disabled(); /* Check for CPU stalls, if enabled. */ check_cpu_stall(rdp); /* Does this CPU need a deferred NOCB wakeup? */ if (rcu_nocb_need_deferred_wakeup(rdp, RCU_NOCB_WAKE)) return 1; /* Is this a nohz_full CPU in userspace or idle? (Ignore RCU if so.) */ - if ((user || rcu_is_cpu_rrupt_from_idle()) && rcu_nohz_full_cpu()) + if ((user || rcu_is_cpu_rrupt_from_idle() || rcu_recent_guest_exit()) && + rcu_nohz_full_cpu()) return 0; /* Is the RCU core waiting for a quiescent state from this CPU? */ gp_in_progress = rcu_gp_in_progress(); if (rdp->core_needs_qs && !rdp->cpu_no_qs.b.norm && gp_in_progress) return 1; /* Does this CPU have callbacks ready to invoke? */ if (!rcu_rdp_is_offloaded(rdp) && rcu_segcblist_ready_cbs(&rdp->cblist))