From patchwork Tue May 23 12:32:08 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: =?utf-8?q?Ma=C3=ADra_Canal?= X-Patchwork-Id: 13252197 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 gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id E7221C7EE26 for ; Tue, 23 May 2023 12:32:45 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 12C9510E433; Tue, 23 May 2023 12:32:45 +0000 (UTC) Received: from fanzine2.igalia.com (fanzine2.igalia.com [213.97.179.56]) by gabe.freedesktop.org (Postfix) with ESMTPS id 082B310E433 for ; Tue, 23 May 2023 12:32:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=igalia.com; s=20170329; h=Content-Transfer-Encoding:Content-Type:MIME-Version:Message-Id: Date:Subject:Cc:To:From:Sender:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: In-Reply-To:References:List-Id:List-Help:List-Unsubscribe:List-Subscribe: List-Post:List-Owner:List-Archive; bh=0pyKNcI2JmURCBC4BceiezKO9ZUNFiz+fksjZhBjD+Y=; b=VQM90HdXpT8x+OQkR8BMM+7Tdr p1dsurdQjsR6Sxl9TZszUoDIdeNdM9jYYYU5plKcOEXs/Epopdr+3EfCLaMVnhH/2QrWDtvk8kZz2 ohq32OLssVr1wVHezCkPoHXS5wtqaVseCalWPjKKuXLCNjVABN4qyL9NEwY5EPIrJxmTjZ6bSP1wP V3VINUB+YL/h29czAgiMjP7KOJvtHNweGZOQqx9OBWEChO5ULFM8mT1wDp4KL7BBr5wqmPQ2b1Xrc Z4FtTgM+iEYhIkWFrEPERelBQOcZpZLJZ2ypAVW/pV1dPeqb62b5rMs60HEPHvApGtSEswo7HZzyK 9FYwI54w==; Received: from gwsc.sc.usp.br ([143.107.225.16] helo=bowie.sc.usp.br) by fanzine2.igalia.com with esmtpsa (Cipher TLS1.3:ECDHE_X25519__RSA_PSS_RSAE_SHA256__AES_256_GCM:256) (Exim) id 1q1RBr-00GqzX-Mk; Tue, 23 May 2023 14:32:36 +0200 From: =?utf-8?q?Ma=C3=ADra_Canal?= To: David Airlie , Daniel Vetter , Rodrigo Siqueira , Melissa Wen , Haneen Mohammed , Arthur Grillo Subject: [PATCH v2] drm/vkms: Fix race-condition between the hrtimer and the atomic commit Date: Tue, 23 May 2023 09:32:08 -0300 Message-Id: <20230523123207.173976-1-mcanal@igalia.com> X-Mailer: git-send-email 2.40.1 MIME-Version: 1.0 X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: =?utf-8?q?Ma=C3=ADra_Canal?= , dri-devel@lists.freedesktop.org Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" Currently, it is possible for the composer to be set as enabled and then as disabled without a proper call for the vkms_vblank_simulate(). This is problematic, because the driver would skip one CRC output, causing CRC tests to fail. Therefore, we need to make sure that, for each time the composer is set as enabled, a composer job is added to the queue. In order to provide this guarantee, add a mutex that will lock before the composer is set as enabled and will unlock only after the composer job is added to the queue. This way, we can have a guarantee that the driver won't skip a CRC entry. This race-condition is affecting the IGT test "writeback-check-output", making the test fail and also, leaking writeback framebuffers, as the writeback job is queued, but it is not signaled. This patch avoids both problems. [v2]: * Create a new mutex and keep the spinlock across the atomic commit in order to avoid interrupts that could result in deadlocks. Signed-off-by: Maíra Canal Reviewed-by: Arthur Grillo --- drivers/gpu/drm/vkms/vkms_composer.c | 9 +++++++-- drivers/gpu/drm/vkms/vkms_crtc.c | 9 +++++---- drivers/gpu/drm/vkms/vkms_drv.h | 4 +++- 3 files changed, 15 insertions(+), 7 deletions(-) diff --git a/drivers/gpu/drm/vkms/vkms_composer.c b/drivers/gpu/drm/vkms/vkms_composer.c index 906d3df40cdb..b12188fd6b38 100644 --- a/drivers/gpu/drm/vkms/vkms_composer.c +++ b/drivers/gpu/drm/vkms/vkms_composer.c @@ -320,10 +320,15 @@ void vkms_set_composer(struct vkms_output *out, bool enabled) if (enabled) drm_crtc_vblank_get(&out->crtc); - spin_lock_irq(&out->lock); + mutex_lock(&out->enabled_lock); old_enabled = out->composer_enabled; out->composer_enabled = enabled; - spin_unlock_irq(&out->lock); + + /* the composition wasn't enabled, so unlock the lock to make sure the lock + * will be balanced even if we have a failed commit + */ + if (!out->composer_enabled) + mutex_unlock(&out->enabled_lock); if (old_enabled) drm_crtc_vblank_put(&out->crtc); diff --git a/drivers/gpu/drm/vkms/vkms_crtc.c b/drivers/gpu/drm/vkms/vkms_crtc.c index 515f6772b866..3079013c8b32 100644 --- a/drivers/gpu/drm/vkms/vkms_crtc.c +++ b/drivers/gpu/drm/vkms/vkms_crtc.c @@ -16,7 +16,7 @@ static enum hrtimer_restart vkms_vblank_simulate(struct hrtimer *timer) struct drm_crtc *crtc = &output->crtc; struct vkms_crtc_state *state; u64 ret_overrun; - bool ret, fence_cookie; + bool ret, fence_cookie, composer_enabled; fence_cookie = dma_fence_begin_signalling(); @@ -25,15 +25,15 @@ static enum hrtimer_restart vkms_vblank_simulate(struct hrtimer *timer) if (ret_overrun != 1) pr_warn("%s: vblank timer overrun\n", __func__); - spin_lock(&output->lock); ret = drm_crtc_handle_vblank(crtc); if (!ret) DRM_ERROR("vkms failure on handling vblank"); state = output->composer_state; - spin_unlock(&output->lock); + composer_enabled = output->composer_enabled; + mutex_unlock(&output->enabled_lock); - if (state && output->composer_enabled) { + if (state && composer_enabled) { u64 frame = drm_crtc_accurate_vblank_count(crtc); /* update frame_start only if a queued vkms_composer_worker() @@ -292,6 +292,7 @@ int vkms_crtc_init(struct drm_device *dev, struct drm_crtc *crtc, spin_lock_init(&vkms_out->lock); spin_lock_init(&vkms_out->composer_lock); + mutex_init(&vkms_out->enabled_lock); vkms_out->composer_workq = alloc_ordered_workqueue("vkms_composer", 0); if (!vkms_out->composer_workq) diff --git a/drivers/gpu/drm/vkms/vkms_drv.h b/drivers/gpu/drm/vkms/vkms_drv.h index 5f1a0a44a78c..dcf4e302fb4d 100644 --- a/drivers/gpu/drm/vkms/vkms_drv.h +++ b/drivers/gpu/drm/vkms/vkms_drv.h @@ -100,8 +100,10 @@ struct vkms_output { struct workqueue_struct *composer_workq; /* protects concurrent access to composer */ spinlock_t lock; + /* guarantees that if the composer is enabled, a job will be queued */ + struct mutex enabled_lock; - /* protected by @lock */ + /* protected by @enabled_lock */ bool composer_enabled; struct vkms_crtc_state *composer_state;