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 X-Spam-Level: X-Spam-Status: No, score=-13.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 48015C433DF for ; Fri, 24 Jul 2020 21:17:15 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 125B6206F0 for ; Fri, 24 Jul 2020 21:17:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1595625435; bh=mfPXSF2+i1eHAQa5TSjmMc8Vb2jERmjj96FmNHh+D9Q=; h=From:To:Cc:Subject:Date:List-ID:From; b=TXtyy5ZCWcTODMhDo43L+flt2qCJ782NAx8gj14TQIUQtao2ER+2P8vboMqQ7YeGZ u3h4AvVe2ANONCol5qohcmpWt3MyX+TI4k6aKSDk1xrLeAaoc2FmT3n1XwJQhWT9AH vvhWfz+MWd00lxgDy+POoMHkhlJGvVGSR2JZgONc= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726411AbgGXVRO (ORCPT ); Fri, 24 Jul 2020 17:17:14 -0400 Received: from mail.kernel.org ([198.145.29.99]:42170 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726083AbgGXVRO (ORCPT ); Fri, 24 Jul 2020 17:17:14 -0400 Received: from mail.kernel.org (unknown [104.132.0.74]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 33EC8206F0; Fri, 24 Jul 2020 21:17:12 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1595625432; bh=mfPXSF2+i1eHAQa5TSjmMc8Vb2jERmjj96FmNHh+D9Q=; h=From:To:Cc:Subject:Date:From; b=Lct1zlvYPrlDwLiP40dTIC/HcT1zlGF09v+Gddbf69iscE3k/+uJBMirnOpAeJiQI TxF8/dSX+RJMmJu+kiyeLcT6iki44jxBIkh7lq875av9wzY7dG7YsKFlL0ymgBB5gn IQNhJZ+qfS9X/qV6Z7IdBmMRNkhr7/AWkTX4KYjA= From: Stephen Boyd To: Andy Gross , Bjorn Andersson Cc: Stephen Boyd , linux-kernel@vger.kernel.org, linux-arm-msm@vger.kernel.org, Douglas Anderson , Maulik Shah , Lina Iyer Subject: [PATCH v2] soc: qcom: rpmh-rsc: Sleep waiting for tcs slots to be free Date: Fri, 24 Jul 2020 14:17:11 -0700 Message-Id: <20200724211711.810009-1-sboyd@kernel.org> X-Mailer: git-send-email 2.28.0.rc0.142.g3c755180ce-goog MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-arm-msm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-arm-msm@vger.kernel.org From: Stephen Boyd The busy loop in rpmh_rsc_send_data() is written with the assumption that the udelay will be preempted by the tcs_tx_done() irq handler when the TCS slots are all full. This doesn't hold true when the calling thread is an irqthread and the tcs_tx_done() irq is also an irqthread. That's because kernel irqthreads are SCHED_FIFO and thus need to voluntarily give up priority by calling into the scheduler so that other threads can run. I see RCU stalls when I boot with irqthreads on the kernel commandline because the modem remoteproc driver is trying to send an rpmh async message from an irqthread that needs to give up the CPU for the rpmh irqthread to run and clear out tcs slots. rcu: INFO: rcu_preempt self-detected stall on CPU rcu: 0-....: (1 GPs behind) idle=402/1/0x4000000000000002 softirq=2108/2109 fqs=4920 (t=21016 jiffies g=2933 q=590) Task dump for CPU 0: irq/11-smp2p R running task 0 148 2 0x00000028 Call trace: dump_backtrace+0x0/0x154 show_stack+0x20/0x2c sched_show_task+0xfc/0x108 dump_cpu_task+0x44/0x50 rcu_dump_cpu_stacks+0xa4/0xf8 rcu_sched_clock_irq+0x7dc/0xaa8 update_process_times+0x30/0x54 tick_sched_handle+0x50/0x64 tick_sched_timer+0x4c/0x8c __hrtimer_run_queues+0x21c/0x36c hrtimer_interrupt+0xf0/0x22c arch_timer_handler_phys+0x40/0x50 handle_percpu_devid_irq+0x114/0x25c __handle_domain_irq+0x84/0xc4 gic_handle_irq+0xd0/0x178 el1_irq+0xbc/0x180 save_return_addr+0x18/0x28 return_address+0x54/0x88 preempt_count_sub+0x40/0x88 _raw_spin_unlock_irqrestore+0x4c/0x6c ___ratelimit+0xd0/0x128 rpmh_rsc_send_data+0x24c/0x378 __rpmh_write+0x1b0/0x208 rpmh_write_async+0x90/0xbc rpmhpd_send_corner+0x60/0x8c rpmhpd_aggregate_corner+0x8c/0x124 rpmhpd_set_performance_state+0x8c/0xbc _genpd_set_performance_state+0xdc/0x1b8 dev_pm_genpd_set_performance_state+0xb8/0xf8 q6v5_pds_disable+0x34/0x60 [qcom_q6v5_mss] qcom_msa_handover+0x38/0x44 [qcom_q6v5_mss] q6v5_handover_interrupt+0x24/0x3c [qcom_q6v5] handle_nested_irq+0xd0/0x138 qcom_smp2p_intr+0x188/0x200 irq_thread_fn+0x2c/0x70 irq_thread+0xfc/0x14c kthread+0x11c/0x12c ret_from_fork+0x10/0x18 This busy loop naturally lends itself to using a wait queue so that each thread that tries to send a message will sleep waiting on the waitqueue and only be woken up when a free slot is available. This should make things more predictable too because the scheduler will be able to sleep tasks that are waiting on a free tcs instead of the busy loop we currently have today. Cc: Douglas Anderson Cc: Maulik Shah Cc: Lina Iyer Signed-off-by: Stephen Boyd --- Changes in v2: * Document tcs_wait * Move wake_up() outside of the spinlock * Document claim_tcs_for_req() drivers/soc/qcom/rpmh-internal.h | 4 ++ drivers/soc/qcom/rpmh-rsc.c | 115 +++++++++++++++---------------- 2 files changed, 58 insertions(+), 61 deletions(-) diff --git a/drivers/soc/qcom/rpmh-internal.h b/drivers/soc/qcom/rpmh-internal.h index ef60e790a750..344ba687c13b 100644 --- a/drivers/soc/qcom/rpmh-internal.h +++ b/drivers/soc/qcom/rpmh-internal.h @@ -8,6 +8,7 @@ #define __RPM_INTERNAL_H__ #include +#include #include #define TCS_TYPE_NR 4 @@ -106,6 +107,8 @@ struct rpmh_ctrlr { * @lock: Synchronize state of the controller. If RPMH's cache * lock will also be held, the order is: drv->lock then * cache_lock. + * @tcs_wait: Wait queue used to wait for @tcs_in_use to free up a + * slot * @client: Handle to the DRV's client. */ struct rsc_drv { @@ -118,6 +121,7 @@ struct rsc_drv { struct tcs_group tcs[TCS_TYPE_NR]; DECLARE_BITMAP(tcs_in_use, MAX_TCS_NR); spinlock_t lock; + wait_queue_head_t tcs_wait; struct rpmh_ctrlr client; }; diff --git a/drivers/soc/qcom/rpmh-rsc.c b/drivers/soc/qcom/rpmh-rsc.c index 076fd27f3081..84a27b884af0 100644 --- a/drivers/soc/qcom/rpmh-rsc.c +++ b/drivers/soc/qcom/rpmh-rsc.c @@ -19,6 +19,7 @@ #include #include #include +#include #include #include @@ -445,6 +446,7 @@ static irqreturn_t tcs_tx_done(int irq, void *p) if (!drv->tcs[ACTIVE_TCS].num_tcs) enable_tcs_irq(drv, i, false); spin_unlock(&drv->lock); + wake_up(&drv->tcs_wait); if (req) rpmh_tx_done(req, err); } @@ -563,73 +565,34 @@ static int find_free_tcs(struct tcs_group *tcs) } /** - * tcs_write() - Store messages into a TCS right now, or return -EBUSY. + * claim_tcs_for_req() - Claim a tcs in the given tcs_group; only for active. * @drv: The controller. + * @tcs: The tcs_group used for ACTIVE_ONLY transfers. * @msg: The data to be sent. * - * Grabs a TCS for ACTIVE_ONLY transfers and writes the messages to it. + * Claims a tcs in the given tcs_group while making sure that no existing cmd + * is in flight that would conflict with the one in @msg. * - * If there are no free TCSes for ACTIVE_ONLY transfers or if a command for - * the same address is already transferring returns -EBUSY which means the - * client should retry shortly. + * Context: Must be called with the drv->lock held since that protects + * tcs_in_use. * - * Return: 0 on success, -EBUSY if client should retry, or an error. - * Client should have interrupts enabled for a bit before retrying. + * Return: The id of the claimed tcs or -EBUSY if a matching msg is in flight + * or the tcs_group is full. */ -static int tcs_write(struct rsc_drv *drv, const struct tcs_request *msg) +static int claim_tcs_for_req(struct rsc_drv *drv, struct tcs_group *tcs, + const struct tcs_request *msg) { - struct tcs_group *tcs; - int tcs_id; - unsigned long flags; int ret; - tcs = get_tcs_for_msg(drv, msg); - if (IS_ERR(tcs)) - return PTR_ERR(tcs); - - spin_lock_irqsave(&drv->lock, flags); /* * The h/w does not like if we send a request to the same address, * when one is already in-flight or being processed. */ ret = check_for_req_inflight(drv, tcs, msg); if (ret) - goto unlock; - - ret = find_free_tcs(tcs); - if (ret < 0) - goto unlock; - tcs_id = ret; - - tcs->req[tcs_id - tcs->offset] = msg; - set_bit(tcs_id, drv->tcs_in_use); - if (msg->state == RPMH_ACTIVE_ONLY_STATE && tcs->type != ACTIVE_TCS) { - /* - * Clear previously programmed WAKE commands in selected - * repurposed TCS to avoid triggering them. tcs->slots will be - * cleaned from rpmh_flush() by invoking rpmh_rsc_invalidate() - */ - write_tcs_reg_sync(drv, RSC_DRV_CMD_ENABLE, tcs_id, 0); - write_tcs_reg_sync(drv, RSC_DRV_CMD_WAIT_FOR_CMPL, tcs_id, 0); - enable_tcs_irq(drv, tcs_id, true); - } - spin_unlock_irqrestore(&drv->lock, flags); - - /* - * These two can be done after the lock is released because: - * - We marked "tcs_in_use" under lock. - * - Once "tcs_in_use" has been marked nobody else could be writing - * to these registers until the interrupt goes off. - * - The interrupt can't go off until we trigger w/ the last line - * of __tcs_set_trigger() below. - */ - __tcs_buffer_write(drv, tcs_id, 0, msg); - __tcs_set_trigger(drv, tcs_id, true); + return ret; - return 0; -unlock: - spin_unlock_irqrestore(&drv->lock, flags); - return ret; + return find_free_tcs(tcs); } /** @@ -656,18 +619,47 @@ static int tcs_write(struct rsc_drv *drv, const struct tcs_request *msg) */ int rpmh_rsc_send_data(struct rsc_drv *drv, const struct tcs_request *msg) { - int ret; + struct tcs_group *tcs; + int tcs_id; + unsigned long flags; - do { - ret = tcs_write(drv, msg); - if (ret == -EBUSY) { - pr_info_ratelimited("TCS Busy, retrying RPMH message send: addr=%#x\n", - msg->cmds[0].addr); - udelay(10); - } - } while (ret == -EBUSY); + tcs = get_tcs_for_msg(drv, msg); + if (IS_ERR(tcs)) + return PTR_ERR(tcs); - return ret; + spin_lock_irqsave(&drv->lock, flags); + + /* Wait forever for a free tcs. It better be there eventually! */ + wait_event_lock_irq(drv->tcs_wait, + (tcs_id = claim_tcs_for_req(drv, tcs, msg)) >= 0, + drv->lock); + + tcs->req[tcs_id - tcs->offset] = msg; + set_bit(tcs_id, drv->tcs_in_use); + if (msg->state == RPMH_ACTIVE_ONLY_STATE && tcs->type != ACTIVE_TCS) { + /* + * Clear previously programmed WAKE commands in selected + * repurposed TCS to avoid triggering them. tcs->slots will be + * cleaned from rpmh_flush() by invoking rpmh_rsc_invalidate() + */ + write_tcs_reg_sync(drv, RSC_DRV_CMD_ENABLE, tcs_id, 0); + write_tcs_reg_sync(drv, RSC_DRV_CMD_WAIT_FOR_CMPL, tcs_id, 0); + enable_tcs_irq(drv, tcs_id, true); + } + spin_unlock_irqrestore(&drv->lock, flags); + + /* + * These two can be done after the lock is released because: + * - We marked "tcs_in_use" under lock. + * - Once "tcs_in_use" has been marked nobody else could be writing + * to these registers until the interrupt goes off. + * - The interrupt can't go off until we trigger w/ the last line + * of __tcs_set_trigger() below. + */ + __tcs_buffer_write(drv, tcs_id, 0, msg); + __tcs_set_trigger(drv, tcs_id, true); + + return 0; } /** @@ -975,6 +967,7 @@ static int rpmh_rsc_probe(struct platform_device *pdev) return ret; spin_lock_init(&drv->lock); + init_waitqueue_head(&drv->tcs_wait); bitmap_zero(drv->tcs_in_use, MAX_TCS_NR); irq = platform_get_irq(pdev, drv->id); -- Sent by a computer, using git, on the internet