Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754113AbaDPET0 (ORCPT ); Wed, 16 Apr 2014 00:19:26 -0400 Received: from cantor2.suse.de ([195.135.220.15]:38849 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754022AbaDPETX (ORCPT ); Wed, 16 Apr 2014 00:19:23 -0400 From: NeilBrown To: linux-mm@kvack.org, linux-nfs@vger.kernel.org, linux-kernel@vger.kernel.org Date: Wed, 16 Apr 2014 14:03:36 +1000 Subject: [PATCH 13/19] MM: set PF_FSTRANS while allocating per-cpu memory to avoid deadlock. Cc: xfs@oss.sgi.com Message-ID: <20140416040336.10604.67456.stgit@notabene.brown> In-Reply-To: <20140416033623.10604.69237.stgit@notabene.brown> References: <20140416033623.10604.69237.stgit@notabene.brown> User-Agent: StGit/0.16 MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org lockdep reports a locking chain sk_lock-AF_INET --> rtnl_mutex --> pcpu_alloc_mutex As sk_lock may be needed to reclaim memory, allowing that reclaim while pcu_alloc_mutex is held can lead to deadlock. So set PF_FSTRANS while it is help to avoid the FS reclaim. pcpu_alloc_mutex can be taken when rtnl_mutex is held: [] pcpu_alloc+0x49/0x960 [] __alloc_percpu+0xb/0x10 [] loopback_dev_init+0x17/0x60 [] register_netdevice+0xec/0x550 [] register_netdev+0x15/0x30 Signed-off-by: NeilBrown --- mm/percpu.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/mm/percpu.c b/mm/percpu.c index 036cfe07050f..77dd24032f41 100644 --- a/mm/percpu.c +++ b/mm/percpu.c @@ -712,6 +712,7 @@ static void __percpu *pcpu_alloc(size_t size, size_t align, bool reserved) int slot, off, new_alloc; unsigned long flags; void __percpu *ptr; + unsigned int pflags; if (unlikely(!size || size > PCPU_MIN_UNIT_SIZE || align > PAGE_SIZE)) { WARN(true, "illegal size (%zu) or align (%zu) for " @@ -720,6 +721,7 @@ static void __percpu *pcpu_alloc(size_t size, size_t align, bool reserved) } mutex_lock(&pcpu_alloc_mutex); + current_set_flags_nested(&pflags, PF_FSTRANS); spin_lock_irqsave(&pcpu_lock, flags); /* serve reserved allocations from the reserved chunk if available */ @@ -801,6 +803,7 @@ area_found: goto fail_unlock; } + current_restore_flags_nested(&pflags, PF_FSTRANS); mutex_unlock(&pcpu_alloc_mutex); /* return address relative to base address */ @@ -811,6 +814,7 @@ area_found: fail_unlock: spin_unlock_irqrestore(&pcpu_lock, flags); fail_unlock_mutex: + current_restore_flags_nested(&pflags, PF_FSTRANS); mutex_unlock(&pcpu_alloc_mutex); if (warn_limit) { pr_warning("PERCPU: allocation failed, size=%zu align=%zu, " -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/