From patchwork Mon May 11 07:57:03 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Chris Wilson X-Patchwork-Id: 11539887 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 7484C912 for ; Mon, 11 May 2020 07:58:03 +0000 (UTC) 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 mail.kernel.org (Postfix) with ESMTPS id 5D35520735 for ; Mon, 11 May 2020 07:58:03 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 5D35520735 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=chris-wilson.co.uk Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=intel-gfx-bounces@lists.freedesktop.org Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 56AF36E220; Mon, 11 May 2020 07:58:00 +0000 (UTC) X-Original-To: intel-gfx@lists.freedesktop.org Delivered-To: intel-gfx@lists.freedesktop.org Received: from fireflyinternet.com (mail.fireflyinternet.com [109.228.58.192]) by gabe.freedesktop.org (Postfix) with ESMTPS id B30946E220 for ; Mon, 11 May 2020 07:57:58 +0000 (UTC) X-Default-Received-SPF: pass (skip=forwardok (res=PASS)) x-ip-name=78.156.65.138; Received: from build.alporthouse.com (unverified [78.156.65.138]) by fireflyinternet.com (Firefly Internet (M1)) with ESMTP id 21160785-1500050 for multiple; Mon, 11 May 2020 08:57:24 +0100 From: Chris Wilson To: intel-gfx@lists.freedesktop.org Date: Mon, 11 May 2020 08:57:03 +0100 Message-Id: <20200511075722.13483-1-chris@chris-wilson.co.uk> X-Mailer: git-send-email 2.20.1 MIME-Version: 1.0 Subject: [Intel-gfx] [PATCH 01/20] drm/i915/gt: Mark up the racy read of execlists->context_tag X-BeenThere: intel-gfx@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Intel graphics driver community testing & development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Chris Wilson Errors-To: intel-gfx-bounces@lists.freedesktop.org Sender: "Intel-gfx" Since we are using bitops on context_tag to allow us to reserve and release inflight tags concurrently, the scan for the next bit is intentionally racy. [ 516.446854] BUG: KCSAN: data-race in execlists_schedule_in.isra.0 [i915] / execlists_schedule_out [i915] [ 516.446874] [ 516.446886] write (marked) to 0xffff8881f7644048 of 8 bytes by interrupt on cpu 2: [ 516.447076] execlists_schedule_out+0x538/0x6a0 [i915] [ 516.447263] process_csb+0x10b/0x3d0 [i915] [ 516.447449] execlists_submission_tasklet+0x30/0x170 [i915] [ 516.447468] tasklet_action_common.isra.0+0x42/0x90 [ 516.447484] __do_softirq+0xc8/0x206 [ 516.447498] irq_exit+0xcd/0xe0 [ 516.447516] do_IRQ+0x44/0xc0 [ 516.447535] ret_from_intr+0x0/0x1c [ 516.447550] cpuidle_enter_state+0x199/0x400 [ 516.447572] cpuidle_enter+0x50/0x90 [ 516.447587] do_idle+0x197/0x1e0 [ 516.447600] cpu_startup_entry+0x14/0x20 [ 516.447619] start_secondary+0xf9/0x130 [ 516.447643] secondary_startup_64+0xa4/0xb0 [ 516.447655] [ 516.447671] read to 0xffff8881f7644048 of 8 bytes by task 460 on cpu 1: [ 516.447863] execlists_schedule_in.isra.0+0x3cf/0x5a0 [i915] [ 516.448064] execlists_dequeue+0xf8f/0x1690 [i915] [ 516.448252] __execlists_submission_tasklet+0x48/0x60 [i915] [ 516.448440] execlists_submit_request+0x2e2/0x310 [i915] [ 516.448634] submit_notify+0x8f/0xc8 [i915] [ 516.448820] __i915_sw_fence_complete+0x61/0x420 [i915] [ 516.449005] i915_sw_fence_complete+0x58/0x80 [i915] [ 516.449208] i915_sw_fence_commit+0x16/0x20 [i915] [ 516.449399] __i915_request_queue+0x60/0x70 [i915] [ 516.449590] i915_gem_do_execbuffer+0x33f1/0x4a00 [i915] [ 516.449782] i915_gem_execbuffer2_ioctl+0x2a2/0x550 [i915] [ 516.449800] drm_ioctl_kernel+0xe9/0x130 [ 516.449814] drm_ioctl+0x27d/0x45e [ 516.449827] ksys_ioctl+0x89/0xb0 [ 516.449842] __x64_sys_ioctl+0x42/0x60 [ 516.449864] do_syscall_64+0x6e/0x2c0 [ 516.449878] entry_SYSCALL_64_after_hwframe+0x44/0xa9 Signed-off-by: Chris Wilson Reviewed-by: Mika Kuoppala --- drivers/gpu/drm/i915/gt/intel_lrc.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/gpu/drm/i915/gt/intel_lrc.c b/drivers/gpu/drm/i915/gt/intel_lrc.c index 8e254f639751..ed45fc40f884 100644 --- a/drivers/gpu/drm/i915/gt/intel_lrc.c +++ b/drivers/gpu/drm/i915/gt/intel_lrc.c @@ -1367,7 +1367,7 @@ __execlists_schedule_in(struct i915_request *rq) ce->lrc.ccid = ce->tag; } else { /* We don't need a strict matching tag, just different values */ - unsigned int tag = ffs(engine->context_tag); + unsigned int tag = ffs(READ_ONCE(engine->context_tag)); GEM_BUG_ON(tag == 0 || tag >= BITS_PER_LONG); clear_bit(tag - 1, &engine->context_tag);