From patchwork Fri Feb 16 19:43:29 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Luis Chamberlain X-Patchwork-Id: 13560504 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id B3743433B0; Fri, 16 Feb 2024 19:43:31 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=198.137.202.133 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1708112613; cv=none; b=UXXDvf6vMNx+Yyws5J9213yupQ5XSdfmuJn0FQNycFCzhncDD6O7WsnOHv0Vkx0H+GOuIyH4XklWYsXjbu1ODbumZ/+YwtDN/0S4KG136/dYv8rgO0IynvebOMz0xUKuuJQECB+a331SgT/cXvApPgSye4AKT/dQPh0lzbpdDB0= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1708112613; c=relaxed/simple; bh=yNyHPZtxa5jU0ks+mH7ZDBSKGV9sQTZ/GmsXwVvVMhw=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=Xz1khV/kTedG3Ghx+oakOWfpRviNDrrI6OTpjeN7q9gnv3+MtMXbDnqN1qfoQTG38T/eltyGj9VbqExbEakQpEJz8WPbrx+AnHtlC+EMSLeyFnItBBabpXRc0jc+VXCDW88D0elwNivSzhDSG0oSNrmEM6NGnlZoU+wqaIvJPX0= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org; spf=none smtp.mailfrom=infradead.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b=owRcMhkv; arc=none smtp.client-ip=198.137.202.133 Authentication-Results: smtp.subspace.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=infradead.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="owRcMhkv" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20210309; h=Sender:Content-Transfer-Encoding: MIME-Version:Message-ID:Date:Subject:Cc:To:From:Reply-To:Content-Type: Content-ID:Content-Description:In-Reply-To:References; bh=JIBYKrHmraGn0Qv35tDBtlGinkhRJwFyg9FJtFLUQ5w=; b=owRcMhkvsO9GVbii6oW8q+GWe1 dwoWp3Fgl1UHLXCCxepniozgLA+wTKFO0nEyuy16XKn5SNR5vbimxmlk6GTIn8ow92LNuxTcN6rTm ZNto7Uzzu+qKz4kQ5crgnuG8SPOVFSeOnv7bs3eu5l/yObnDR+SAMdGRdAZPZDHkQrQpxLfl0fA8k vlaO+FaU3OnZl1XW7Gz+85hrCErHErBoE9w741qyc5H19aaJlJgYQv3rL0TfSe5Eugrx3PnR5ZVuN 8D0nEvSQ9RnaKuWS74WIjzem8ayqdFwbbGoDtOnI6nQHyHE6jxzP6bWCBKjWfsa4hxv/hvXasCuHp 4B24ayMw==; Received: from mcgrof by bombadil.infradead.org with local (Exim 4.97.1 #2 (Red Hat Linux)) id 1rb47O-00000003WfT-2ZJh; Fri, 16 Feb 2024 19:43:30 +0000 From: Luis Chamberlain To: akpm@linux-foundation.org, willy@infradead.org Cc: linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, gost.dev@samsung.com, p.raghav@samsung.com, da.gomez@samsung.com, mcgrof@kernel.org, kernel test robot Subject: [PATCH] test_xarray: fix soft lockup for advanced-api tests Date: Fri, 16 Feb 2024 11:43:29 -0800 Message-ID: <20240216194329.840555-1-mcgrof@kernel.org> X-Mailer: git-send-email 2.43.0 Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Sender: Luis Chamberlain The new adanced API tests want to vet the xarray API is doing what it promises by manually iterating over a set of possible indexes on its own, and using a query operation which holds the RCU lock and then releases it. So it is not using the helper loop options which xarray provides on purpose. Any loop which iterates over 1 million entries (which is possible with order 20, so emulating say a 4 GiB block size) to just to rcu lock and unlock will eventually end up triggering a soft lockup on systems which don't preempt, and have lock provin and RCU prooving enabled. xarray users already use XA_CHECK_SCHED for loops which may take a long time, in our case we don't want to RCU unlock and lock as the caller does that already, but rather just force a schedule every XA_CHECK_SCHED iterations since the test is trying to not trust and rather test that xarray is doing the right thing. [0] https://lkml.kernel.org/r/202402071613.70f28243-lkp@intel.com Reported-by: kernel test robot Signed-off-by: Luis Chamberlain Reported-by: kernel test robot --- lib/test_xarray.c | 12 ++++++++++++ 1 file changed, 12 insertions(+) diff --git a/lib/test_xarray.c b/lib/test_xarray.c index d4e55b4867dc..ac162025cc59 100644 --- a/lib/test_xarray.c +++ b/lib/test_xarray.c @@ -781,6 +781,7 @@ static noinline void *test_get_entry(struct xarray *xa, unsigned long index) { XA_STATE(xas, xa, index); void *p; + static unsigned int i = 0; rcu_read_lock(); repeat: @@ -790,6 +791,17 @@ static noinline void *test_get_entry(struct xarray *xa, unsigned long index) goto repeat; rcu_read_unlock(); + /* + * This is not part of the page cache, this selftest is pretty + * aggressive and does not want to trust the xarray API but rather + * test it, and for order 20 (4 GiB block size) we can loop over + * over a million entries which can cause a soft lockup. Page cache + * APIs won't be stupid, proper page cache APIs loop over the proper + * order so when using a larger order we skip shared entries. + */ + if (++i % XA_CHECK_SCHED == 0) + schedule(); + return p; }