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 891FBC77B7A for ; Wed, 17 May 2023 15:23:48 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 60F3510E442; Wed, 17 May 2023 15:23:48 +0000 (UTC) Received: from mga05.intel.com (mga05.intel.com [192.55.52.43]) by gabe.freedesktop.org (Postfix) with ESMTPS id CF02210E442 for ; Wed, 17 May 2023 15:23:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1684337025; x=1715873025; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=ptfXmbXArsfCcnj1bt1RHBZ7kAA6Y3eMhFAcajGyNcA=; b=H3k4VYOmicm682n1sfujUZT0enPeejgjGNyIcyW+xMSSC8XjMJQ6ccKL a7uxQLddYzq1F2/SSEQmFwAvY3/eOoGCYthAphmulaOtKJp6yM4W0LFIH i0YldVgUJsUrfSbCOqUJbL68Ro4myp2OHvhPk80Z1GPV3MfNHVfA3/nDn 4MPgkHrlS9xYz4lSXE74wvZVACaAtCgcem7+oGWarr8EdeJKDnNf7cU7v yZkP1KW2cS/ETD/cb+cMsi5QEznWlnmiuN4l26vpuR/oGBDp+hJ1G12FU O+7XrTI7+fjbHe2eGWAYRXL+ZloMjHbO5/uDPcnhPRH5w2T76FYqJnH5Y A==; X-IronPort-AV: E=McAfee;i="6600,9927,10713"; a="438132158" X-IronPort-AV: E=Sophos;i="5.99,282,1677571200"; d="scan'208";a="438132158" Received: from fmsmga001.fm.intel.com ([10.253.24.23]) by fmsmga105.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 17 May 2023 08:23:45 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=McAfee;i="6600,9927,10713"; a="846129314" X-IronPort-AV: E=Sophos;i="5.99,282,1677571200"; d="scan'208";a="846129314" Received: from fskirtun-mobl-g8.ger.corp.intel.com (HELO mwauld-desk1.intel.com) ([10.252.15.194]) by fmsmga001-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 17 May 2023 08:23:44 -0700 From: Matthew Auld To: intel-xe@lists.freedesktop.org Date: Wed, 17 May 2023 16:22:43 +0100 Message-Id: <20230517152244.348171-6-matthew.auld@intel.com> X-Mailer: git-send-email 2.40.1 In-Reply-To: <20230517152244.348171-1-matthew.auld@intel.com> References: <20230517152244.348171-1-matthew.auld@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Subject: [Intel-xe] [PATCH v5 6/7] drm/xe: fix xe_device_mem_access_get() races 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: , Cc: Rodrigo Vivi Errors-To: intel-xe-bounces@lists.freedesktop.org Sender: "Intel-xe" It looks like there is at least one race here, given that the pm_runtime_suspended() check looks to return false if we are in the process of suspending the device (RPM_SUSPENDING vs RPM_SUSPENDED). We later also do xe_pm_runtime_get_if_active(), but since the device is suspending or has now suspended, this doesn't do anything either. Following from this we can potentially return from xe_device_mem_access_get() with the device suspended or about to be, leading to broken behaviour. Attempt to fix this by always grabbing the runtime ref when our internal ref transitions from 0 -> 1, and then wrap the whole thing with a lock to ensure callers are serialized. v2: - ct->lock looks to be primed with fs_reclaim, so holding that and then allocating memory will cause lockdep to complain. Now that we unconditionally grab the mem_access.lock around mem_access_{get,put}, we need to change the ordering wrt to grabbing the ct->lock, since some of the runtime_pm routines can allocate memory (or at least that's what lockdep seems to suggest). Hopefully not a big deal. It might be that there were already issues with this, just that the atomics where "hiding" the potential issues. v3: - Use Thomas Hellström' idea with tracking the active task that is executing in the resume or suspend callback, in order to avoid recursive resume/suspend calls deadlocking on itself. - Split the ct->lock change. v4: - Add smb_mb() around accessing the pm_callback_task for extra safety (Thomas Hellström) Closes: https://gitlab.freedesktop.org/drm/xe/kernel/-/issues/258 Signed-off-by: Matthew Auld Cc: Rodrigo Vivi Cc: Thomas Hellström Cc: Matthew Brost --- drivers/gpu/drm/xe/xe_device.c | 52 +++++++++++++++++++--- drivers/gpu/drm/xe/xe_device.h | 17 +------ drivers/gpu/drm/xe/xe_device_types.h | 11 ++++- drivers/gpu/drm/xe/xe_pm.c | 66 +++++++++++++++++++--------- drivers/gpu/drm/xe/xe_pm.h | 3 +- 5 files changed, 104 insertions(+), 45 deletions(-) diff --git a/drivers/gpu/drm/xe/xe_device.c b/drivers/gpu/drm/xe/xe_device.c index d0297ee432b2..55f974b1ee78 100644 --- a/drivers/gpu/drm/xe/xe_device.c +++ b/drivers/gpu/drm/xe/xe_device.c @@ -403,24 +403,62 @@ u32 xe_device_ccs_bytes(struct xe_device *xe, u64 size) DIV_ROUND_UP(size, NUM_BYTES_PER_CCS_BYTE) : 0; } +void xe_device_assert_mem_access(struct xe_device *xe) +{ + if (xe_pm_read_callback_task(xe) == current) + return; + + XE_WARN_ON(!xe->mem_access.ref); +} + +bool xe_device_mem_access_ongoing(struct xe_device *xe) +{ + bool ret; + + if (xe_pm_read_callback_task(xe) == current) + return true; + + mutex_lock(&xe->mem_access.lock); + ret = xe->mem_access.ref; + mutex_unlock(&xe->mem_access.lock); + + return ret; +} + void xe_device_mem_access_get(struct xe_device *xe) { - bool resumed = xe_pm_runtime_resume_if_suspended(xe); + /* + * This looks racy, but should be fine since the pm_callback_task only + * transitions from NULL -> current (and back to NULL again), during the + * runtime_resume() or runtime_suspend() callbacks, for which there can + * only be a single one running for our device. We only need to prevent + * recursively calling the runtime_get or runtime_put from those + * callbacks, as well as preventing triggering any access_ongoing + * asserts. + */ + if (xe_pm_read_callback_task(xe) == current) + return; + /* + * It's possible to get rid of the mem_access.lock here, however lockdep + * has an easier time digesting the mem_access.lock -> runtime_pm chain + * (and any locks the caller is holding), on all transitions, and not + * for example just on the 0 -> 1. + */ mutex_lock(&xe->mem_access.lock); - if (xe->mem_access.ref++ == 0) - xe->mem_access.hold_rpm = xe_pm_runtime_get_if_active(xe); + if (xe->mem_access.ref == 0) + xe->mem_access.hold_rpm = xe_pm_runtime_resume_and_get(xe); + xe->mem_access.ref++; mutex_unlock(&xe->mem_access.lock); - /* The usage counter increased if device was immediately resumed */ - if (resumed) - xe_pm_runtime_put(xe); - XE_WARN_ON(xe->mem_access.ref == S32_MAX); } void xe_device_mem_access_put(struct xe_device *xe) { + if (xe_pm_read_callback_task(xe) == current) + return; + mutex_lock(&xe->mem_access.lock); if (--xe->mem_access.ref == 0 && xe->mem_access.hold_rpm) xe_pm_runtime_put(xe); diff --git a/drivers/gpu/drm/xe/xe_device.h b/drivers/gpu/drm/xe/xe_device.h index 9ab7e6134f89..64576ed9323e 100644 --- a/drivers/gpu/drm/xe/xe_device.h +++ b/drivers/gpu/drm/xe/xe_device.h @@ -90,21 +90,8 @@ static inline struct xe_force_wake * gt_to_fw(struct xe_gt *gt) void xe_device_mem_access_get(struct xe_device *xe); void xe_device_mem_access_put(struct xe_device *xe); -static inline void xe_device_assert_mem_access(struct xe_device *xe) -{ - XE_WARN_ON(!xe->mem_access.ref); -} - -static inline bool xe_device_mem_access_ongoing(struct xe_device *xe) -{ - bool ret; - - mutex_lock(&xe->mem_access.lock); - ret = xe->mem_access.ref; - mutex_unlock(&xe->mem_access.lock); - - return ret; -} +void xe_device_assert_mem_access(struct xe_device *xe); +bool xe_device_mem_access_ongoing(struct xe_device *xe); static inline bool xe_device_in_fault_mode(struct xe_device *xe) { diff --git a/drivers/gpu/drm/xe/xe_device_types.h b/drivers/gpu/drm/xe/xe_device_types.h index 0b6860156574..b0c69fcb4065 100644 --- a/drivers/gpu/drm/xe/xe_device_types.h +++ b/drivers/gpu/drm/xe/xe_device_types.h @@ -256,7 +256,10 @@ struct xe_device { * triggering additional actions when they occur. */ struct { - /** @lock: protect the ref count */ + /** + * @lock: Serialize xe_device_mem_access users, + * and protect the below internal state, like @ref. + */ struct mutex lock; /** @ref: ref count of memory accesses */ s32 ref; @@ -264,6 +267,12 @@ struct xe_device { bool hold_rpm; } mem_access; + /** + * @pm_callback_task: Track the active task that is running in either + * the runtime_suspend or runtime_resume callbacks. + */ + struct task_struct *pm_callback_task; + /** @d3cold_allowed: Indicates if d3cold is a valid device state */ bool d3cold_allowed; diff --git a/drivers/gpu/drm/xe/xe_pm.c b/drivers/gpu/drm/xe/xe_pm.c index b7b57f10ba25..29c8861e58a5 100644 --- a/drivers/gpu/drm/xe/xe_pm.c +++ b/drivers/gpu/drm/xe/xe_pm.c @@ -137,43 +137,71 @@ void xe_pm_runtime_fini(struct xe_device *xe) pm_runtime_forbid(dev); } +static void xe_pm_write_callback_task(struct xe_device *xe, + struct task_struct *task) +{ + WRITE_ONCE(xe->pm_callback_task, task); + + /* + * Just in case it's somehow possible for our writes to be reordered to + * the extent that something else re-uses the task written in + * pm_callback_task. For example after returning from the callback, but + * before the reordered write that resets pm_callback_task back to NULL. + */ + smp_mb(); /* pairs with xe_pm_read_callback_task */ +} + +struct task_struct *xe_pm_read_callback_task(struct xe_device *xe) +{ + smp_mb(); /* pairs with xe_pm_write_callback_task */ + + return READ_ONCE(xe->pm_callback_task); +} + int xe_pm_runtime_suspend(struct xe_device *xe) { struct xe_gt *gt; u8 id; - int err; + int err = 0; + + if (xe->d3cold_allowed && xe_device_mem_access_ongoing(xe)) + return -EBUSY; + + /* Disable access_ongoing asserts and prevent recursive pm calls */ + xe_pm_write_callback_task(xe, current); if (xe->d3cold_allowed) { - if (xe_device_mem_access_ongoing(xe)) - return -EBUSY; - err = xe_bo_evict_all(xe); if (err) - return err; + goto out; } for_each_gt(gt, xe, id) { err = xe_gt_suspend(gt); if (err) - return err; + goto out; } xe_irq_suspend(xe); - - return 0; +out: + xe_pm_write_callback_task(xe, NULL); + return err; } int xe_pm_runtime_resume(struct xe_device *xe) { struct xe_gt *gt; u8 id; - int err; + int err = 0; + + /* Disable access_ongoing asserts and prevent recursive pm calls */ + xe_pm_write_callback_task(xe, current); if (xe->d3cold_allowed) { for_each_gt(gt, xe, id) { err = xe_pcode_init(gt); if (err) - return err; + goto out; } /* @@ -182,7 +210,7 @@ int xe_pm_runtime_resume(struct xe_device *xe) */ err = xe_bo_restore_kernel(xe); if (err) - return err; + goto out; } xe_irq_resume(xe); @@ -193,10 +221,11 @@ int xe_pm_runtime_resume(struct xe_device *xe) if (xe->d3cold_allowed) { err = xe_bo_restore_user(xe); if (err) - return err; + goto out; } - - return 0; +out: + xe_pm_write_callback_task(xe, NULL); + return err; } int xe_pm_runtime_get(struct xe_device *xe) @@ -210,14 +239,9 @@ int xe_pm_runtime_put(struct xe_device *xe) return pm_runtime_put_autosuspend(xe->drm.dev); } -/* Return true if resume operation happened and usage count was increased */ -bool xe_pm_runtime_resume_if_suspended(struct xe_device *xe) +bool xe_pm_runtime_resume_and_get(struct xe_device *xe) { - /* In case we are suspended we need to immediately wake up */ - if (pm_runtime_suspended(xe->drm.dev)) - return !pm_runtime_resume_and_get(xe->drm.dev); - - return false; + return !pm_runtime_resume_and_get(xe->drm.dev); } int xe_pm_runtime_get_if_active(struct xe_device *xe) diff --git a/drivers/gpu/drm/xe/xe_pm.h b/drivers/gpu/drm/xe/xe_pm.h index 6a885585f653..e92c508d44b9 100644 --- a/drivers/gpu/drm/xe/xe_pm.h +++ b/drivers/gpu/drm/xe/xe_pm.h @@ -19,7 +19,8 @@ int xe_pm_runtime_suspend(struct xe_device *xe); int xe_pm_runtime_resume(struct xe_device *xe); int xe_pm_runtime_get(struct xe_device *xe); int xe_pm_runtime_put(struct xe_device *xe); -bool xe_pm_runtime_resume_if_suspended(struct xe_device *xe); +bool xe_pm_runtime_resume_and_get(struct xe_device *xe); int xe_pm_runtime_get_if_active(struct xe_device *xe); +struct task_struct *xe_pm_read_callback_task(struct xe_device *xe); #endif -- 2.40.1