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=-9.9 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS autolearn=unavailable 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 31F01C388F7 for ; Wed, 28 Oct 2020 22:29:56 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D07AE20714 for ; Wed, 28 Oct 2020 22:29:55 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="cZCIwdRl" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2387640AbgJ1W3y (ORCPT ); Wed, 28 Oct 2020 18:29:54 -0400 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:25114 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2387593AbgJ1W33 (ORCPT ); Wed, 28 Oct 2020 18:29:29 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1603924168; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding; bh=wn0Z2b/sXqhg3H37/VXFagrRrbv7yUzOhfS3vczwgWY=; b=cZCIwdRlyrPWeqDIrj0cwOREmv8PtRwYT9+3tSLgRBmqNkgQyvIgY53geAMblVi0NDnQrk iZB7ygmwooRRpnsWHe5J2o7OuxgCgV6P4vvLafVI3PmzTKdjA8UN2b/QV4TJroKsefxRrM L7UjEYAKjFznyRHtuvDst/H8/X4so0M= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-234-GY6_39BMMkWttzhIjBAwzw-1; Wed, 28 Oct 2020 11:27:43 -0400 X-MC-Unique: GY6_39BMMkWttzhIjBAwzw-1 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 5514FE9008; Wed, 28 Oct 2020 15:27:41 +0000 (UTC) Received: from localhost.localdomain.com (ovpn-66-92.rdu2.redhat.com [10.10.66.92]) by smtp.corp.redhat.com (Postfix) with ESMTP id 21F1810013C1; Wed, 28 Oct 2020 15:27:40 +0000 (UTC) From: Qian Cai To: Michael Ellerman Cc: Oliver O'Halloran , Russell Currey , Benjamin Herrenschmidt , Paul Mackerras , linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org Subject: [PATCH] powerpc/eeh_cache: Fix a possible debugfs deadlock Date: Wed, 28 Oct 2020 11:27:17 -0400 Message-Id: <20201028152717.8967-1-cai@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Lockdep complains that a possible deadlock below in eeh_addr_cache_show() because it is acquiring a lock with IRQ enabled, but eeh_addr_cache_insert_dev() needs to acquire the same lock with IRQ disabled. Let's just make eeh_addr_cache_show() acquire the lock with IRQ disabled as well. CPU0 CPU1 ---- ---- lock(&pci_io_addr_cache_root.piar_lock); local_irq_disable(); lock(&tp->lock); lock(&pci_io_addr_cache_root.piar_lock); lock(&tp->lock); *** DEADLOCK *** lock_acquire+0x140/0x5f0 _raw_spin_lock_irqsave+0x64/0xb0 eeh_addr_cache_insert_dev+0x48/0x390 eeh_probe_device+0xb8/0x1a0 pnv_pcibios_bus_add_device+0x3c/0x80 pcibios_bus_add_device+0x118/0x290 pci_bus_add_device+0x28/0xe0 pci_bus_add_devices+0x54/0xb0 pcibios_init+0xc4/0x124 do_one_initcall+0xac/0x528 kernel_init_freeable+0x35c/0x3fc kernel_init+0x24/0x148 ret_from_kernel_thread+0x5c/0x80 lock_acquire+0x140/0x5f0 _raw_spin_lock+0x4c/0x70 eeh_addr_cache_show+0x38/0x110 seq_read+0x1a0/0x660 vfs_read+0xc8/0x1f0 ksys_read+0x74/0x130 system_call_exception+0xf8/0x1d0 system_call_common+0xe8/0x218 Fixes: 5ca85ae6318d ("powerpc/eeh_cache: Add a way to dump the EEH address cache") Signed-off-by: Qian Cai --- arch/powerpc/kernel/eeh_cache.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/arch/powerpc/kernel/eeh_cache.c b/arch/powerpc/kernel/eeh_cache.c index 6b50bf15d8c1..bf3270426d82 100644 --- a/arch/powerpc/kernel/eeh_cache.c +++ b/arch/powerpc/kernel/eeh_cache.c @@ -264,8 +264,9 @@ static int eeh_addr_cache_show(struct seq_file *s, void *v) { struct pci_io_addr_range *piar; struct rb_node *n; + unsigned long flags; - spin_lock(&pci_io_addr_cache_root.piar_lock); + spin_lock_irqsave(&pci_io_addr_cache_root.piar_lock, flags); for (n = rb_first(&pci_io_addr_cache_root.rb_root); n; n = rb_next(n)) { piar = rb_entry(n, struct pci_io_addr_range, rb_node); @@ -273,7 +274,7 @@ static int eeh_addr_cache_show(struct seq_file *s, void *v) (piar->flags & IORESOURCE_IO) ? "i/o" : "mem", &piar->addr_lo, &piar->addr_hi, pci_name(piar->pcidev)); } - spin_unlock(&pci_io_addr_cache_root.piar_lock); + spin_unlock_irqrestore(&pci_io_addr_cache_root.piar_lock, flags); return 0; } -- 2.28.0