From mboxrd@z Thu Jan 1 00:00:00 1970 From: Eric Dumazet Subject: [PATCH] net: remove a WARN_ON() in net_enable_timestamp() Date: Fri, 22 Mar 2013 17:38:28 -0700 Message-ID: <1363999108.4431.81.camel@edumazet-glaptop> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Cc: netdev , Laurent Chavey To: David Miller Return-path: Received: from mail-pa0-f43.google.com ([209.85.220.43]:52449 "EHLO mail-pa0-f43.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933549Ab3CWAib (ORCPT ); Fri, 22 Mar 2013 20:38:31 -0400 Received: by mail-pa0-f43.google.com with SMTP id rl6so172038pac.16 for ; Fri, 22 Mar 2013 17:38:30 -0700 (PDT) Sender: netdev-owner@vger.kernel.org List-ID: From: Eric Dumazet The WARN_ON(in_interrupt()) in net_enable_timestamp() can get false positive, in socket clone path, run from softirq context : [ 3641.624425] WARNING: at net/core/dev.c:1532 net_enable_timestamp+0x7b/0x80() [ 3641.668811] Call Trace: [ 3641.671254] [] warn_slowpath_common+0x87/0xc0 [ 3641.677871] [] warn_slowpath_null+0x1a/0x20 [ 3641.683683] [] net_enable_timestamp+0x7b/0x80 [ 3641.689668] [] sk_clone_lock+0x425/0x450 [ 3641.695222] [] inet_csk_clone_lock+0x16/0x170 [ 3641.701213] [] tcp_create_openreq_child+0x29/0x820 [ 3641.707663] [] ? ipt_do_table+0x222/0x670 [ 3641.713354] [] tcp_v4_syn_recv_sock+0xab/0x3d0 [ 3641.719425] [] tcp_check_req+0x3da/0x530 [ 3641.724979] [] ? inet_hashinfo_init+0x60/0x80 [ 3641.730964] [] ? tcp_v4_rcv+0x79f/0xbe0 [ 3641.736430] [] tcp_v4_do_rcv+0x38d/0x4f0 [ 3641.741985] [] tcp_v4_rcv+0xa7a/0xbe0 Its safe at this point because the parent socket owns a reference on the netstamp_needed, so we cant have a 0 -> 1 transition, which requires to lock a mutex. Instead of refining the check, lets remove it, as all known callers are safe. If it ever changes in the future, static_key_slow_inc() will complain anyway. Reported-by: Laurent Chavey Signed-off-by: Eric Dumazet --- net/core/dev.c | 1 - 1 file changed, 1 deletion(-) diff --git a/net/core/dev.c b/net/core/dev.c index d540ced..b13e5c7 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -1545,7 +1545,6 @@ void net_enable_timestamp(void) return; } #endif - WARN_ON(in_interrupt()); static_key_slow_inc(&netstamp_needed); } EXPORT_SYMBOL(net_enable_timestamp);