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 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 59084E6ADE4 for ; Mon, 22 Dec 2025 20:20:01 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 88FFC10E2BE; Mon, 22 Dec 2025 20:20:00 +0000 (UTC) Authentication-Results: gabe.freedesktop.org; dkim=pass (2048-bit key; unprotected) header.d=intel.com header.i=@intel.com header.b="JfU/+Saw"; dkim-atps=neutral Received: from mgamail.intel.com (mgamail.intel.com [198.175.65.18]) by gabe.freedesktop.org (Postfix) with ESMTPS id 8E11D10E05C for ; Mon, 22 Dec 2025 20:19:59 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1766434799; x=1797970799; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=bPlJ+mqFR76T2AqJWdJ2pnbq/4q5mZI9dcZwvIjvyiI=; b=JfU/+SawoXJXZmYGpRqOE3u0wRF1I/k+9d8Pl9l7Ft/eQC7sgqbruC3+ T+JI9YS7AtdNeSV+Yi1aE7aTazHX7qJAoJdTsCbAt1TFNAjZusvL2VVSm 5vN3Oljr/XZw2L8J0HUFD0mEDoY63dcwfxm+we3tXrDcou+5hJEd1rCWJ nBlnNzFNRKvKiURVXAaJozrctzYCbzEXe9gKtwdMK4Q+do1KcehbE8Ycq DqWDIDLrTToknjB68zmH4WAU4ZWS5OV2XV3JXKc0kwlj/RNBfizgZvUHC ClSfkpP1P2dOkG3FI/0qlM+SkJNwcuciSrDHA9NHk3e9DAv2owmrJMNLD g==; X-CSE-ConnectionGUID: T3Qnsg7fSj2+d8Wwkr9ipw== X-CSE-MsgGUID: 484JPeRaT/mWDddqMGxu8A== X-IronPort-AV: E=McAfee;i="6800,10657,11650"; a="68335794" X-IronPort-AV: E=Sophos;i="6.21,169,1763452800"; d="scan'208";a="68335794" Received: from fmviesa009.fm.intel.com ([10.60.135.149]) by orvoesa110.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 22 Dec 2025 12:19:58 -0800 X-CSE-ConnectionGUID: rnpv48uhRVOCb3K3Fa+RMw== X-CSE-MsgGUID: 2lJ1Omm1Rjmhab7NoIR76g== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.21,169,1763452800"; d="scan'208";a="200100907" Received: from dut4086lnl.fm.intel.com ([10.105.10.207]) by fmviesa009-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 22 Dec 2025 12:19:58 -0800 From: Jonathan Cavitt To: intel-xe@lists.freedesktop.org Cc: saurabhg.gupta@intel.com, alex.zuo@intel.com, jonathan.cavitt@intel.com, matthew.brost@intel.com, daniele.ceraolospurio@intel.com, rodrigo.vivi@intel.com, michal.wajdeczko@intel.com, stuart.summers@intel.com, ashutosh.dixit@intel.com Subject: [PATCH v3 2/2] drm/xe/guc: READ/WRITE_ONCE ct->state Date: Mon, 22 Dec 2025 20:20:00 +0000 Message-ID: <20251222201957.63245-6-jonathan.cavitt@intel.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20251222201957.63245-4-jonathan.cavitt@intel.com> References: <20251222201957.63245-4-jonathan.cavitt@intel.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-BeenThere: intel-xe@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Intel Xe graphics driver List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: intel-xe-bounces@lists.freedesktop.org Sender: "Intel-xe" Use READ_ONCE and WRITE_ONCE when operating on ct->state to prevent the compiler form ignoring important modifications to its value. Suggested-by: Matthew Brost Signed-off-by: Jonathan Cavitt Cc: Rodrigo Vivi Cc: Michal Wajdeczko Cc: Daniele Ceraolo Spurio --- drivers/gpu/drm/xe/xe_guc_ct.c | 7 ++++++- drivers/gpu/drm/xe/xe_guc_ct.h | 6 ++++-- 2 files changed, 10 insertions(+), 3 deletions(-) diff --git a/drivers/gpu/drm/xe/xe_guc_ct.c b/drivers/gpu/drm/xe/xe_guc_ct.c index f2148a8bf208..dfbf76037b04 100644 --- a/drivers/gpu/drm/xe/xe_guc_ct.c +++ b/drivers/gpu/drm/xe/xe_guc_ct.c @@ -529,7 +529,12 @@ static void guc_ct_change_state(struct xe_guc_ct *ct, if (ct->g2h_outstanding) xe_pm_runtime_put(ct_to_xe(ct)); ct->g2h_outstanding = 0; - ct->state = state; + + /* + * WRITE_ONCE pairs with READ_ONCEs in xe_guc_ct_initialized and + * xe_guc_ct_enabled. + */ + WRITE_ONCE(ct->state, state); xe_gt_dbg(gt, "GuC CT communication channel %s\n", state == XE_GUC_CT_STATE_STOPPED ? "stopped" : diff --git a/drivers/gpu/drm/xe/xe_guc_ct.h b/drivers/gpu/drm/xe/xe_guc_ct.h index 5599939f8fe1..767365a33dee 100644 --- a/drivers/gpu/drm/xe/xe_guc_ct.h +++ b/drivers/gpu/drm/xe/xe_guc_ct.h @@ -30,12 +30,14 @@ void xe_guc_ct_print(struct xe_guc_ct *ct, struct drm_printer *p, bool want_ctb) static inline bool xe_guc_ct_initialized(struct xe_guc_ct *ct) { - return ct->state != XE_GUC_CT_STATE_NOT_INITIALIZED; + /* READ_ONCE pairs with WRITE_ONCE in guc_ct_change_state. */ + return READ_ONCE(ct->state) != XE_GUC_CT_STATE_NOT_INITIALIZED; } static inline bool xe_guc_ct_enabled(struct xe_guc_ct *ct) { - return ct->state == XE_GUC_CT_STATE_ENABLED; + /* READ_ONCE pairs with WRITE_ONCE in guc_ct_change_state. */ + return READ_ONCE(ct->state) == XE_GUC_CT_STATE_ENABLED; } static inline void xe_guc_ct_irq_handler(struct xe_guc_ct *ct) -- 2.43.0