From patchwork Tue Sep 26 19:05:17 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Teres Alexis, Alan Previn" X-Patchwork-Id: 13399620 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 D42FDE7E65A for ; Tue, 26 Sep 2023 19:05:33 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 65FD310E16B; Tue, 26 Sep 2023 19:05:23 +0000 (UTC) Received: from mgamail.intel.com (mgamail.intel.com [134.134.136.100]) by gabe.freedesktop.org (Postfix) with ESMTPS id 4A4838920D; Tue, 26 Sep 2023 19:05:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1695755121; x=1727291121; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=F+gEMX3R5obvLjWgcz+YdVyybtLP39gJApRETU6QBkU=; b=PQgGCuEgPZIfkJqiJlDQxAtIMHnwNPiVNWIJlwXef7dKk/3/XaHYy/Uo NRzsrATmNnhau/YBOUt/Ttbs/o6uVNn+mRHHuaMX170fA3fkvQGziUrJY YHL+GxgD6WRCDmOX7gX4+1gfgYuCoDZSgy/2kAf3Pvt0zYYlTFKn6txZR jn1w2I8HWadxVEkN9iLefrjlEeoRBnNV0kTMec+0qsH8oQRGpt2TBKh5+ b/qDHg9IhCWUNwgiRT8Y7EgSPwTvme1Y3rLnn8mvwlJLo2ppuOUMRI02J qddqRG3Rh197KdWS+G5qefKOuJcGuYrbtcYb3K/diBhkq+eg7+zvtUAXC w==; X-IronPort-AV: E=McAfee;i="6600,9927,10845"; a="448141896" X-IronPort-AV: E=Sophos;i="6.03,178,1694761200"; d="scan'208";a="448141896" Received: from fmsmga004.fm.intel.com ([10.253.24.48]) by orsmga105.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 26 Sep 2023 12:05:20 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=McAfee;i="6600,9927,10845"; a="819142181" X-IronPort-AV: E=Sophos;i="6.03,178,1694761200"; d="scan'208";a="819142181" Received: from aalteres-desk.fm.intel.com ([10.80.57.53]) by fmsmga004.fm.intel.com with ESMTP; 26 Sep 2023 12:05:19 -0700 From: Alan Previn To: intel-gfx@lists.freedesktop.org Subject: [PATCH v4 2/3] drm/i915/guc: Close deregister-context race against CT-loss Date: Tue, 26 Sep 2023 12:05:17 -0700 Message-Id: <20230926190518.105393-3-alan.previn.teres.alexis@intel.com> X-Mailer: git-send-email 2.39.0 In-Reply-To: <20230926190518.105393-1-alan.previn.teres.alexis@intel.com> References: <20230926190518.105393-1-alan.previn.teres.alexis@intel.com> 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: , Alan Previn , Anshuman Gupta , dri-devel@lists.freedesktop.org, Daniele Ceraolo Spurio , Rodrigo Vivi , intel.com@freedesktop.org, Mousumi Jana , John Harrison Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" If we are at the end of suspend or very early in resume its possible an async fence signal (via rcu_call) is triggered to free_engines which could lead us to the execution of the context destruction worker (after a prior worker flush). Thus, when suspending, insert an rcu_barrier at the start of wait_for_suspend so that all such cases have completed and context destruction list isn't missing anything. In destroyed_worker_func, close the race against CT-loss by checking that CT is enabled before calling into deregister_destroyed_contexts. Based on testing, guc_lrc_desc_unpin may still race and fail as we traverse the GuC's context-destroy list because the CT could be disabled right before calling GuC's CT send function. We've witnessed this race condition once every ~6000-8000 suspend-resume cycles while ensuring workloads that render something onscreen is continuously started just before we suspend (and the workload is small enough to complete and trigger the queued engine/context free-up either very late in suspend or very early in resume). In such a case, we need to unroll the entire process because guc-lrc-unpin takes a gt wakeref which only gets released in the G2H IRQ reply that never comes through in this corner case. Without the unroll, the taken wakeref is leaked and will cascade into a kernel hang later at the tail end of suspend in this function: intel_wakeref_wait_for_idle(>->wakeref) (called by) - intel_gt_pm_wait_for_idle (called by) - wait_for_suspend Thus, do an unroll in guc_lrc_desc_unpin and deregister_destroyed_- contexts if guc_lrc_desc_unpin fails due to CT send falure. When unrolling, keep the context in the GuC's destroy-list so it can get picked up on the next destroy worker invocation (if suspend aborted) or get fully purged as part of a GuC sanitization (end of suspend) or a reset flow. Signed-off-by: Alan Previn Signed-off-by: Anshuman Gupta Tested-by: Mousumi Jana --- drivers/gpu/drm/i915/gt/intel_gt_pm.c | 7 ++ .../gpu/drm/i915/gt/uc/intel_guc_submission.c | 81 ++++++++++++++++--- 2 files changed, 77 insertions(+), 11 deletions(-) diff --git a/drivers/gpu/drm/i915/gt/intel_gt_pm.c b/drivers/gpu/drm/i915/gt/intel_gt_pm.c index 5a942af0a14e..59b5658a17fb 100644 --- a/drivers/gpu/drm/i915/gt/intel_gt_pm.c +++ b/drivers/gpu/drm/i915/gt/intel_gt_pm.c @@ -289,6 +289,13 @@ int intel_gt_resume(struct intel_gt *gt) static void wait_for_suspend(struct intel_gt *gt) { + /* + * On rare occasions, we've observed the fence completion trigger + * free_engines asynchronously via rcu_call. Ensure those are done. + * This path is only called on suspend, so it's an acceptable cost. + */ + rcu_barrier(); + if (!intel_gt_pm_is_awake(gt)) return; diff --git a/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c b/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c index fdd7179f502a..465baf7660d7 100644 --- a/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c +++ b/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c @@ -235,6 +235,13 @@ set_context_destroyed(struct intel_context *ce) ce->guc_state.sched_state |= SCHED_STATE_DESTROYED; } +static inline void +clr_context_destroyed(struct intel_context *ce) +{ + lockdep_assert_held(&ce->guc_state.lock); + ce->guc_state.sched_state &= ~SCHED_STATE_DESTROYED; +} + static inline bool context_pending_disable(struct intel_context *ce) { return ce->guc_state.sched_state & SCHED_STATE_PENDING_DISABLE; @@ -612,6 +619,8 @@ static int guc_submission_send_busy_loop(struct intel_guc *guc, u32 g2h_len_dw, bool loop) { + int ret; + /* * We always loop when a send requires a reply (i.e. g2h_len_dw > 0), * so we don't handle the case where we don't get a reply because we @@ -622,7 +631,11 @@ static int guc_submission_send_busy_loop(struct intel_guc *guc, if (g2h_len_dw) atomic_inc(&guc->outstanding_submission_g2h); - return intel_guc_send_busy_loop(guc, action, len, g2h_len_dw, loop); + ret = intel_guc_send_busy_loop(guc, action, len, g2h_len_dw, loop); + if (ret) + atomic_dec(&guc->outstanding_submission_g2h); + + return ret; } int intel_guc_wait_for_pending_msg(struct intel_guc *guc, @@ -3205,12 +3218,13 @@ static void guc_context_close(struct intel_context *ce) spin_unlock_irqrestore(&ce->guc_state.lock, flags); } -static inline void guc_lrc_desc_unpin(struct intel_context *ce) +static inline int guc_lrc_desc_unpin(struct intel_context *ce) { struct intel_guc *guc = ce_to_guc(ce); struct intel_gt *gt = guc_to_gt(guc); unsigned long flags; bool disabled; + int ret; GEM_BUG_ON(!intel_gt_pm_is_awake(gt)); GEM_BUG_ON(!ctx_id_mapped(guc, ce->guc_id.id)); @@ -3220,19 +3234,38 @@ static inline void guc_lrc_desc_unpin(struct intel_context *ce) /* Seal race with Reset */ spin_lock_irqsave(&ce->guc_state.lock, flags); disabled = submission_disabled(guc); - if (likely(!disabled)) { - __intel_gt_pm_get(gt); - set_context_destroyed(ce); - clr_context_registered(ce); - } - spin_unlock_irqrestore(&ce->guc_state.lock, flags); if (unlikely(disabled)) { + spin_unlock_irqrestore(&ce->guc_state.lock, flags); release_guc_id(guc, ce); __guc_context_destroy(ce); - return; + return 0; } - deregister_context(ce, ce->guc_id.id); + /* GuC is active, lets destroy this context, + * but at this point we can still be racing with + * suspend, so we undo everything if the H2G fails + */ + + /* Change context state to destroyed and get gt-pm */ + __intel_gt_pm_get(gt); + set_context_destroyed(ce); + clr_context_registered(ce); + + ret = deregister_context(ce, ce->guc_id.id); + if (ret) { + /* Undo the state change and put gt-pm if that failed */ + set_context_registered(ce); + clr_context_destroyed(ce); + /* + * Dont use might_sleep / ASYNC verion of put because + * CT loss in deregister_context could mean an ongoing + * reset or suspend flow. Immediately put before the unlock + */ + __intel_wakeref_put(>->wakeref, 0); + } + spin_unlock_irqrestore(&ce->guc_state.lock, flags); + + return ret; } static void __guc_context_destroy(struct intel_context *ce) @@ -3300,7 +3333,22 @@ static void deregister_destroyed_contexts(struct intel_guc *guc) if (!ce) break; - guc_lrc_desc_unpin(ce); + if (guc_lrc_desc_unpin(ce)) { + /* + * This means GuC's CT link severed mid-way which could happen + * in suspend-resume corner cases. In this case, put the + * context back into the destroyed_contexts list which will + * get picked up on the next context deregistration event or + * purged in a GuC sanitization event (reset/unload/wedged/...). + */ + spin_lock_irqsave(&guc->submission_state.lock, flags); + list_add_tail(&ce->destroyed_link, + &guc->submission_state.destroyed_contexts); + spin_unlock_irqrestore(&guc->submission_state.lock, flags); + /* Bail now since the list might never be emptied if h2gs fail */ + break; + } + } } @@ -3311,6 +3359,17 @@ static void destroyed_worker_func(struct work_struct *w) struct intel_gt *gt = guc_to_gt(guc); int tmp; + /* + * In rare cases we can get here via async context-free fence-signals that + * come very late in suspend flow or very early in resume flows. In these + * cases, GuC won't be ready but just skipping it here is fine as these + * pending-destroy-contexts get destroyed totally at GuC reset time at the + * end of suspend.. OR.. this worker can be picked up later on the next + * context destruction trigger after resume-completes + */ + if (!intel_guc_is_ready(guc)) + return; + with_intel_gt_pm(gt, tmp) deregister_destroyed_contexts(guc); }