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 X-Spam-Level: X-Spam-Status: No, score=-13.6 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id B5455C07E9B for ; Wed, 21 Jul 2021 11:26:26 +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 6CE576101B for ; Wed, 21 Jul 2021 11:26:26 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 6CE576101B Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=ffwll.ch Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=dri-devel-bounces@lists.freedesktop.org Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 03C0B6EBAC; Wed, 21 Jul 2021 11:26:26 +0000 (UTC) Received: from mail-wr1-x430.google.com (mail-wr1-x430.google.com [IPv6:2a00:1450:4864:20::430]) by gabe.freedesktop.org (Postfix) with ESMTPS id 23AB96EBAC for ; Wed, 21 Jul 2021 11:26:25 +0000 (UTC) Received: by mail-wr1-x430.google.com with SMTP id d2so1846195wrn.0 for ; Wed, 21 Jul 2021 04:26:25 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ffwll.ch; s=google; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=SHXTqODjZMjL7ems7eQOdMuntJ59DwSRCnurAgLXpD8=; b=VASvrozaCGnLisNK4Xlibl8ySlOT/+g5WuAkRQmPLaRyufdY5KTxqw8UKAjaGvdID8 DtiexV9zlca8dOa1kvCUhp8ZoG6eWFzUdRUM2YFQY9KQd0QOwzdrGMHMPDnthnvKUjVC HYLCdWxLR6AvLKc4k42IkPFKdNFvk6lnbkrsg= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=SHXTqODjZMjL7ems7eQOdMuntJ59DwSRCnurAgLXpD8=; b=Q6+0QB5X6Bo3tVNYV9qaN94HgECxGhl+SeKWvIMXKt5PLc3YJtKyA4R0anafdnc929 IxXfR2Iam2IO72rglzOh23zaUzsnSDRj7WX+70JBTEpV/lpxdMCIA/ghGXJbGjJQuRLB jY6KM0CfcF0jB4HXGv3uc1AjaJgA5wdXED02tkBDPJlZ6AzJG7G49loHqlZ8huRsUELa zEtZvi4UlPzhUg2a+ARr8JJAW1TnWbIGrOitwp3oN0fMxCTU5TckkAFOZw8PZ97LDElK N0rR9/WuXQcsPAPYIP+VAYQLVd/36YOg1XqmgjcPsGFvqb4ukE6DuVntrqByHIX1JxG2 /4Ag== X-Gm-Message-State: AOAM530Fj/te9CA5s62PiJpt0jolsmmpTGHuGkt0VbFKqPQzcUzICDm6 7+SOYYXWoQuAxhfYRKFwUDg5oq46KcOnbg== X-Google-Smtp-Source: ABdhPJxI4G9Kh4w4H5hhaSS3JGjdwP4S1wByysNecFr4KR5xj440C3JjB0XJMswp9lbNU3vAAHhMLA== X-Received: by 2002:a5d:4b46:: with SMTP id w6mr42766727wrs.352.1626866783761; Wed, 21 Jul 2021 04:26:23 -0700 (PDT) Received: from phenom.ffwll.local ([2a02:168:57f4:0:efd0:b9e5:5ae6:c2fa]) by smtp.gmail.com with ESMTPSA id u16sm32090963wrw.36.2021.07.21.04.26.23 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 21 Jul 2021 04:26:23 -0700 (PDT) Date: Wed, 21 Jul 2021 13:26:21 +0200 From: Daniel Vetter To: Jason Ekstrand Subject: Re: [PATCH 3/6] drm/i915: Always call i915_globals_exit() from i915_exit() Message-ID: References: <20210719183047.2624569-1-jason@jlekstrand.net> <20210719183047.2624569-4-jason@jlekstrand.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Operating-System: Linux phenom 5.10.0-7-amd64 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: Intel GFX , Maling list - DRI developers Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" On Tue, Jul 20, 2021 at 09:55:22AM -0500, Jason Ekstrand wrote: > On Tue, Jul 20, 2021 at 9:18 AM Daniel Vetter wrote: > > > > On Mon, Jul 19, 2021 at 01:30:44PM -0500, Jason Ekstrand wrote: > > > If the driver was not fully loaded, we may still have globals lying > > > around. If we don't tear those down in i915_exit(), we'll leak a bunch > > > of memory slabs. This can happen two ways: use_kms = false and if we've > > > run mock selftests. In either case, we have an early exit from > > > i915_init which happens after i915_globals_init() and we need to clean > > > up those globals. While we're here, add an explicit boolean instead of > > > using a random field from i915_pci_device to detect partial loads. > > > > > > The mock selftests case gets especially sticky. The load isn't entirely > > > a no-op. We actually do quite a bit inside those selftests including > > > allocating a bunch of mock objects and running tests on them. Once all > > > those tests are complete, we exit early from i915_init(). Perviously, > > > i915_init() would return a non-zero error code on failure and a zero > > > error code on success. In the success case, we would get to i915_exit() > > > and check i915_pci_driver.driver.owner to detect if i915_init exited early > > > and do nothing. In the failure case, we would fail i915_init() but > > > there would be no opportunity to clean up globals. > > > > > > The most annoying part is that you don't actually notice the failure as > > > part of the self-tests since leaking a bit of memory, while bad, doesn't > > > result in anything observable from userspace. Instead, the next time we > > > load the driver (usually for next IGT test), i915_globals_init() gets > > > invoked again, we go to allocate a bunch of new memory slabs, those > > > implicitly create debugfs entries, and debugfs warns that we're trying > > > to create directories and files that already exist. Since this all > > > happens as part of the next driver load, it shows up in the dmesg-warn > > > of whatever IGT test ran after the mock selftests. > > > > > > While the obvious thing to do here might be to call i915_globals_exit() > > > after selftests, that's not actually safe. The dma-buf selftests call > > > i915_gem_prime_export which creates a file. We call dma_buf_put() on > > > the resulting dmabuf which calls fput() on the file. However, fput() > > > isn't immediate and gets flushed right before syscall returns. This > > > means that all the fput()s from the selftests don't happen until right > > > before the module load syscall used to fire off the selftests returns > > > which is after i915_init(). If we call i915_globals_exit() in > > > i915_init() after selftests, we end up freeing slabs out from under > > > objects which won't get released until fput() is flushed at the end of > > > the module load. > > > > > > The solution here is to let i915_init() return success early and detect > > > the early success in i915_exit() and only tear down globals and nothing > > > else. This way the module loads successfully, regardless of the success > > > or failure of the tests. Because we've not enumerated any PCI devices, > > > no device nodes are created and it's entirely useless from userspace. > > > The only thing the module does at that point is hold on to a bit of > > > memory until we unload it and i915_exit() is called. Importantly, this > > > means that everything from our selftests has the ability to properly > > > flush out between i915_init() and i915_exit() because there are a couple > > > syscall boundaries in between. > > > > > > Signed-off-by: Jason Ekstrand > > > Fixes: 32eb6bcfdda9 ("drm/i915: Make request allocation caches global") > > > Cc: Daniel Vetter > > > --- > > > drivers/gpu/drm/i915/i915_pci.c | 32 +++++++++++++++++++++++++------- > > > 1 file changed, 25 insertions(+), 7 deletions(-) > > > > > > diff --git a/drivers/gpu/drm/i915/i915_pci.c b/drivers/gpu/drm/i915/i915_pci.c > > > index 4e627b57d31a2..24e4e54516936 100644 > > > --- a/drivers/gpu/drm/i915/i915_pci.c > > > +++ b/drivers/gpu/drm/i915/i915_pci.c > > > @@ -1194,18 +1194,31 @@ static struct pci_driver i915_pci_driver = { > > > .driver.pm = &i915_pm_ops, > > > }; > > > > > > +static bool i915_fully_loaded = false; > > > + > > > static int __init i915_init(void) > > > { > > > bool use_kms = true; > > > int err; > > > > > > + i915_fully_loaded = false; > > > + > > > err = i915_globals_init(); > > > if (err) > > > return err; > > > > > > + /* i915_mock_selftests() only returns zero if no mock subtests were > > > + * run. If we get any non-zero error code, we return early here. > > > + * We always return success because selftests may have allocated > > > + * objects from slabs which will get cleaned up by i915_exit(). We > > > + * could attempt to clean up immediately and fail module load but, > > > + * thanks to interactions with other parts of the kernel (struct > > > + * file, in particular), it's safer to let the module fully load > > > + * and then clean up on unload. > > > + */ > > > err = i915_mock_selftests(); > > > if (err) > > > - return err > 0 ? 0 : err; > > > + return 0; > > > > At least the module options still claim that you can run selftests and > > still load the driver. Which makes sense for perf/hw selftests, since > > those need the driver, but would result in the same old bug resurfacing > > that you're trying to fix there. > > > > Is that description just confused and needs some fixing, or do we have a > > gap here? > > I don't think there's real need for a fully loaded driver after mock > selftests. They exist entirely to run against a mock driver, not the > real one. Can you pls update the module option help then for the next round? -Daniel > > > Patch itself looks reasonable, with the nits from Tvrtko addressed: > > Done > > > Reviewed-by: Daniel Vetter > > Thanks > > --Jason > > > > > > > /* > > > * Enable KMS by default, unless explicitly overriden by > > > @@ -1225,6 +1238,12 @@ static int __init i915_init(void) > > > return 0; > > > } > > > > > > + /* After this point, i915_init() must either fully succeed or > > > + * properly tear everything down and fail. We don't have separate > > > + * flags for each set-up bit. > > > + */ > > > + i915_fully_loaded = true; > > > + > > > i915_pmu_init(); > > > > > > err = pci_register_driver(&i915_pci_driver); > > > @@ -1240,12 +1259,11 @@ static int __init i915_init(void) > > > > > > static void __exit i915_exit(void) > > > { > > > - if (!i915_pci_driver.driver.owner) > > > - return; > > > - > > > - i915_perf_sysctl_unregister(); > > > - pci_unregister_driver(&i915_pci_driver); > > > - i915_pmu_exit(); > > > + if (i915_fully_loaded) { > > > + i915_perf_sysctl_unregister(); > > > + pci_unregister_driver(&i915_pci_driver); > > > + i915_pmu_exit(); > > > + } > > > i915_globals_exit(); > > > } > > > > > > -- > > > 2.31.1 > > > > > > > -- > > Daniel Vetter > > Software Engineer, Intel Corporation > > http://blog.ffwll.ch -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch