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Date: Sun, 14 Aug 2011 10:44:26 -0300 From: Kevin Winchester <kjwinchester@...il.com> To: hadi@...erus.ca, davem@...emloft.net Cc: netdev@...r.kernel.org, LKML <linux-kernel@...r.kernel.org> Subject: sch_generic: warning: the comparison will always evaluate as ‘true’ for the address of ‘noop_qdisc’ will never be NULL With: gcc (GCC) 4.6.1 I noticed the following warning appearing in my build: net/sched/sch_generic.c: In function ‘dev_graft_qdisc’: net/sched/sch_generic.c:678:2: warning: the comparison will always evaluate as ‘true’ for the address of ‘noop_qdisc’ will never be NULL [-Waddress] The code in question runs: /* ... and graft new one */ if (qdisc == NULL) qdisc = &noop_qdisc; dev_queue->qdisc_sleeping = qdisc; rcu_assign_pointer(dev_queue->qdisc, &noop_qdisc); where rcu_assign_pointer has a null check that does not apply to noop_qdisc, which will never be null. My question is, should that really be assigning &noop_qdisc in there? It seems odd to assign &noop_qdisc to qdisc only if qdisc is null, and then unconditionally assign &noop_qdisc into dev_queue->qdisc. Should the line be: rcu_assign_pointer(dev_queue->qdisc, qdisc); instead? Just curious, -- Kevin Winchester -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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