[ 44/68] net: remove a WARN_ON() in net_enable_timestamp()

Greg Kroah-Hartman
2013-04-02T22:24:21Z

From: Eric Dumazet <edumazet@google.com>

[ Upstream commit 9979a55a833883242e3a29f3596676edd7199c46 ]

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] <IRQ> [<ffffffff80286817>] warn_slowpath_common+0x87/0xc0
[ 3641.677871] [<ffffffff8028686a>] warn_slowpath_null+0x1a/0x20
[ 3641.683683] [<ffffffff80742f8b>] net_enable_timestamp+0x7b/0x80
[ 3641.689668] [<ffffffff80732ce5>] sk_clone_lock+0x425/0x450
[ 3641.695222] [<ffffffff8078db36>] inet_csk_clone_lock+0x16/0x170
[ 3641.701213] [<ffffffff807ae449>] tcp_create_openreq_child+0x29/0x820
[ 3641.707663] [<ffffffff807d62e2>] ? ipt_do_table+0x222/0x670
[ 3641.713354] [<ffffffff807aaf5b>] tcp_v4_syn_recv_sock+0xab/0x3d0
[ 3641.719425] [<ffffffff807af63a>] tcp_check_req+0x3da/0x530
[ 3641.724979] [<ffffffff8078b400>] ? inet_hashinfo_init+0x60/0x80
[ 3641.730964] [<ffffffff807ade6f>] ? tcp_v4_rcv+0x79f/0xbe0
[ 3641.736430] [<ffffffff807ab9bd>] tcp_v4_do_rcv+0x38d/0x4f0
[ 3641.741985] [<ffffffff807ae14a>] 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 <chavey@google.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
net/core/dev.c | 1 -
1 file changed, 1 deletion(-)

--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -1482,7 +1482,6 @@ void net_enable_timestamp(void)
return;
}
#endif
- WARN_ON(in_interrupt());
static_key_slow_inc(&netstamp_needed);
}
EXPORT_SYMBOL(net_enable_timestamp);