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=-6.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT 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 B2FD0C433FF for ; Mon, 29 Jul 2019 19:33:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 84ED12171F for ; Mon, 29 Jul 2019 19:33:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1564428793; bh=nS+P0xEdNX2Rityxe+sq+lJ71ZCbNvBhaBhuLMPIssY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=faZQXSq3QXoFUUiSXw9AYxsWa6TRPAZVdUUG47jIXFImG5KrRWPCCim3ikjWkz+co 9uX4IBKOFQ8pwytkkTsYWAgbZm/MMfTNAZm7QUD4Jkt0egCvQH9SAKC8SAIuljkX6M ai266rfmE++tJT/OCTPOheXzUt8TQOscfl0R41Qw= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730308AbfG2TdM (ORCPT ); Mon, 29 Jul 2019 15:33:12 -0400 Received: from mail.kernel.org ([198.145.29.99]:47060 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729812AbfG2TdI (ORCPT ); Mon, 29 Jul 2019 15:33:08 -0400 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id D226F21773; Mon, 29 Jul 2019 19:33:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1564428787; bh=nS+P0xEdNX2Rityxe+sq+lJ71ZCbNvBhaBhuLMPIssY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=h7ZKI7BfrfRh16KfBRNpVDgoPCTJv81EAoiocddUC33F5JR1nLNkxFP7X7jFeZ49t bp7iCVR7/qt7oT7opP9XNpIJGBpkR6QV48IiEx+7acJ/PgCQ7BUHi2CxLQx2Z/vvvR zcgwwFMxKIPrdz72uM3mVScLC4txoWvgNRjKB1CU= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Daniel Jordan , Andrea Parri , Boqun Feng , Herbert Xu , "Paul E. McKenney" , Peter Zijlstra , Steffen Klassert , linux-arch@vger.kernel.org, linux-crypto@vger.kernel.org Subject: [PATCH 4.14 147/293] padata: use smp_mb in padata_reorder to avoid orphaned padata jobs Date: Mon, 29 Jul 2019 21:20:38 +0200 Message-Id: <20190729190835.818681103@linuxfoundation.org> X-Mailer: git-send-email 2.22.0 In-Reply-To: <20190729190820.321094988@linuxfoundation.org> References: <20190729190820.321094988@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Daniel Jordan commit cf144f81a99d1a3928f90b0936accfd3f45c9a0a upstream. Testing padata with the tcrypt module on a 5.2 kernel... # modprobe tcrypt alg="pcrypt(rfc4106(gcm(aes)))" type=3 # modprobe tcrypt mode=211 sec=1 ...produces this splat: INFO: task modprobe:10075 blocked for more than 120 seconds. Not tainted 5.2.0-base+ #16 modprobe D 0 10075 10064 0x80004080 Call Trace: ? __schedule+0x4dd/0x610 ? ring_buffer_unlock_commit+0x23/0x100 schedule+0x6c/0x90 schedule_timeout+0x3b/0x320 ? trace_buffer_unlock_commit_regs+0x4f/0x1f0 wait_for_common+0x160/0x1a0 ? wake_up_q+0x80/0x80 { crypto_wait_req } # entries in braces added by hand { do_one_aead_op } { test_aead_jiffies } test_aead_speed.constprop.17+0x681/0xf30 [tcrypt] do_test+0x4053/0x6a2b [tcrypt] ? 0xffffffffa00f4000 tcrypt_mod_init+0x50/0x1000 [tcrypt] ... The second modprobe command never finishes because in padata_reorder, CPU0's load of reorder_objects is executed before the unlocking store in spin_unlock_bh(pd->lock), causing CPU0 to miss CPU1's increment: CPU0 CPU1 padata_reorder padata_do_serial LOAD reorder_objects // 0 INC reorder_objects // 1 padata_reorder TRYLOCK pd->lock // failed UNLOCK pd->lock CPU0 deletes the timer before returning from padata_reorder and since no other job is submitted to padata, modprobe waits indefinitely. Add a pair of full barriers to guarantee proper ordering: CPU0 CPU1 padata_reorder padata_do_serial UNLOCK pd->lock smp_mb() LOAD reorder_objects INC reorder_objects smp_mb__after_atomic() padata_reorder TRYLOCK pd->lock smp_mb__after_atomic is needed so the read part of the trylock operation comes after the INC, as Andrea points out. Thanks also to Andrea for help with writing a litmus test. Fixes: 16295bec6398 ("padata: Generic parallelization/serialization interface") Signed-off-by: Daniel Jordan Cc: Cc: Andrea Parri Cc: Boqun Feng Cc: Herbert Xu Cc: Paul E. McKenney Cc: Peter Zijlstra Cc: Steffen Klassert Cc: linux-arch@vger.kernel.org Cc: linux-crypto@vger.kernel.org Cc: linux-kernel@vger.kernel.org Signed-off-by: Herbert Xu Signed-off-by: Greg Kroah-Hartman --- kernel/padata.c | 12 ++++++++++++ 1 file changed, 12 insertions(+) --- a/kernel/padata.c +++ b/kernel/padata.c @@ -265,7 +265,12 @@ static void padata_reorder(struct parall * The next object that needs serialization might have arrived to * the reorder queues in the meantime, we will be called again * from the timer function if no one else cares for it. + * + * Ensure reorder_objects is read after pd->lock is dropped so we see + * an increment from another task in padata_do_serial. Pairs with + * smp_mb__after_atomic in padata_do_serial. */ + smp_mb(); if (atomic_read(&pd->reorder_objects) && !(pinst->flags & PADATA_RESET)) mod_timer(&pd->timer, jiffies + HZ); @@ -334,6 +339,13 @@ void padata_do_serial(struct padata_priv list_add_tail(&padata->list, &pqueue->reorder.list); spin_unlock(&pqueue->reorder.lock); + /* + * Ensure the atomic_inc of reorder_objects above is ordered correctly + * with the trylock of pd->lock in padata_reorder. Pairs with smp_mb + * in padata_reorder. + */ + smp_mb__after_atomic(); + put_cpu(); padata_reorder(pd);