From patchwork Tue Sep 26 08:14:51 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Damien Le Moal X-Patchwork-Id: 13398837 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 7DA5FE7D255 for ; Tue, 26 Sep 2023 08:15:38 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233966AbjIZIPm (ORCPT ); Tue, 26 Sep 2023 04:15:42 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42996 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233934AbjIZIPb (ORCPT ); Tue, 26 Sep 2023 04:15:31 -0400 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5529397; Tue, 26 Sep 2023 01:15:24 -0700 (PDT) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6AD97C433CA; Tue, 26 Sep 2023 08:15:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1695716124; bh=5ISZ2rm1XsWohf5fIrMtKwvajdQR6fdIx2ZEQbWXz6s=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=ruDAsjWMQUNt+OaNFc0PHk5BycpmZ6KlIjmU7W3uA1BaSWR5y4/bMRoLXsrRYMSHr AreejXp8DfZ6PAmTrWcYdDOTdY4ZfmZJx8AH/DklF0/LC1aalbq6tGWGxNf/l2idLH B3lJNK/8zBtFZAi/SpWSYMoU2nk0phWg+VAB0a8b1hzH3Iw4KMTdhUMqf7Y+UjZyOi rdHq67Szu5w3GdtLpj/Lusznsltf4IZUr9XokkdKofrqQ7PDmcErYTAfXbnjx5PUSO 1vGY5oX5UuLEfZgiIwEuwvjpA6gnY/vejXWqxx6JZurHw+17Y2OSsnHDTgxGTCKX/4 BeqE/cYYJTRgw== From: Damien Le Moal To: linux-ide@vger.kernel.org Cc: linux-scsi@vger.kernel.org, "Martin K . Petersen" , John Garry , Rodrigo Vivi , Paul Ausbeck , Kai-Heng Feng , Joe Breuer , Geert Uytterhoeven , Chia-Lin Kao Subject: [PATCH v7 07/23] ata: libata-scsi: Fix delayed scsi_rescan_device() execution Date: Tue, 26 Sep 2023 17:14:51 +0900 Message-ID: <20230926081507.69346-8-dlemoal@kernel.org> X-Mailer: git-send-email 2.41.0 In-Reply-To: <20230926081507.69346-1-dlemoal@kernel.org> References: <20230926081507.69346-1-dlemoal@kernel.org> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-scsi@vger.kernel.org Commit 6aa0365a3c85 ("ata: libata-scsi: Avoid deadlock on rescan after device resume") modified ata_scsi_dev_rescan() to check the scsi device "is_suspended" power field to ensure that the scsi device associated with an ATA device is fully resumed when scsi_rescan_device() is executed. However, this fix is problematic as: 1) It relies on a PM internal field that should not be used without PM device locking protection. 2) The check for is_suspended and the call to scsi_rescan_device() are not atomic and a suspend PM event may be triggered between them, casuing scsi_rescan_device() to be called on a suspended device and in that function blocking while holding the scsi device lock. This would deadlock a following resume operation. These problems can trigger PM deadlocks on resume, especially with resume operations triggered quickly after or during suspend operations. E.g., a simple bash script like: for (( i=0; i<10; i++ )); do echo "+2 > /sys/class/rtc/rtc0/wakealarm echo mem > /sys/power/state done that triggers a resume 2 seconds after starting suspending a system can quickly lead to a PM deadlock preventing the system from correctly resuming. Fix this by replacing the check on is_suspended with a check on the return value given by scsi_rescan_device() as that function will fail if called against a suspended device. Also make sure rescan tasks already scheduled are first cancelled before suspending an ata port. Fixes: 6aa0365a3c85 ("ata: libata-scsi: Avoid deadlock on rescan after device resume") Cc: stable@vger.kernel.org Signed-off-by: Damien Le Moal Reviewed-by: Hannes Reinecke Reviewed-by: Niklas Cassel Tested-by: Geert Uytterhoeven Reviewed-by: Martin K. Petersen --- drivers/ata/libata-core.c | 16 ++++++++++++++++ drivers/ata/libata-scsi.c | 33 +++++++++++++++------------------ 2 files changed, 31 insertions(+), 18 deletions(-) diff --git a/drivers/ata/libata-core.c b/drivers/ata/libata-core.c index a0bc01606b30..092372334e92 100644 --- a/drivers/ata/libata-core.c +++ b/drivers/ata/libata-core.c @@ -5168,11 +5168,27 @@ static const unsigned int ata_port_suspend_ehi = ATA_EHI_QUIET static void ata_port_suspend(struct ata_port *ap, pm_message_t mesg) { + /* + * We are about to suspend the port, so we do not care about + * scsi_rescan_device() calls scheduled by previous resume operations. + * The next resume will schedule the rescan again. So cancel any rescan + * that is not done yet. + */ + cancel_delayed_work_sync(&ap->scsi_rescan_task); + ata_port_request_pm(ap, mesg, 0, ata_port_suspend_ehi, false); } static void ata_port_suspend_async(struct ata_port *ap, pm_message_t mesg) { + /* + * We are about to suspend the port, so we do not care about + * scsi_rescan_device() calls scheduled by previous resume operations. + * The next resume will schedule the rescan again. So cancel any rescan + * that is not done yet. + */ + cancel_delayed_work_sync(&ap->scsi_rescan_task); + ata_port_request_pm(ap, mesg, 0, ata_port_suspend_ehi, true); } diff --git a/drivers/ata/libata-scsi.c b/drivers/ata/libata-scsi.c index a69d63e7b919..576bb51cb480 100644 --- a/drivers/ata/libata-scsi.c +++ b/drivers/ata/libata-scsi.c @@ -4756,7 +4756,7 @@ void ata_scsi_dev_rescan(struct work_struct *work) struct ata_link *link; struct ata_device *dev; unsigned long flags; - bool delay_rescan = false; + int ret = 0; mutex_lock(&ap->scsi_scan_mutex); spin_lock_irqsave(ap->lock, flags); @@ -4765,37 +4765,34 @@ void ata_scsi_dev_rescan(struct work_struct *work) ata_for_each_dev(dev, link, ENABLED) { struct scsi_device *sdev = dev->sdev; + /* + * If the port was suspended before this was scheduled, + * bail out. + */ + if (ap->pflags & ATA_PFLAG_SUSPENDED) + goto unlock; + if (!sdev) continue; if (scsi_device_get(sdev)) continue; - /* - * If the rescan work was scheduled because of a resume - * event, the port is already fully resumed, but the - * SCSI device may not yet be fully resumed. In such - * case, executing scsi_rescan_device() may cause a - * deadlock with the PM code on device_lock(). Prevent - * this by giving up and retrying rescan after a short - * delay. - */ - delay_rescan = sdev->sdev_gendev.power.is_suspended; - if (delay_rescan) { - scsi_device_put(sdev); - break; - } - spin_unlock_irqrestore(ap->lock, flags); - scsi_rescan_device(sdev); + ret = scsi_rescan_device(sdev); scsi_device_put(sdev); spin_lock_irqsave(ap->lock, flags); + + if (ret) + goto unlock; } } +unlock: spin_unlock_irqrestore(ap->lock, flags); mutex_unlock(&ap->scsi_scan_mutex); - if (delay_rescan) + /* Reschedule with a delay if scsi_rescan_device() returned an error */ + if (ret) schedule_delayed_work(&ap->scsi_rescan_task, msecs_to_jiffies(5)); }