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Date: Thu, 4 Sep 2025 00:52:20 +0200
From: Florian Westphal <fw@strlen.de>
To: Jakub Kicinski <kuba@kernel.org>
Cc: netdev@vger.kernel.org, Paolo Abeni <pabeni@redhat.com>,
	"David S. Miller" <davem@davemloft.net>,
	Eric Dumazet <edumazet@google.com>, netfilter-devel@vger.kernel.org,
	pablo@netfilter.org
Subject: Re: [PATCH net 1/2] selftests: netfilter: fix udpclash tool hang
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References: <20250902185855.25919-1-fw@strlen.de>
 <20250902185855.25919-2-fw@strlen.de>
 <20250903151554.5c72661e@kernel.org>
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Jakub Kicinski <kuba@kernel.org> wrote:
> On Tue,  2 Sep 2025 20:58:54 +0200 Florian Westphal wrote:
> > Yi Chen reports that 'udpclash' loops forever depending on compiler
> > (and optimization level used); while (x == 1) gets optimized into
> > for (;;).  Switch to stdatomic to prevent this.
> 
> gcc version 15.1.1 (F42) w/ whatever flags kselftests use appear to be
> unaware of this macro:
> 
> udpclash.c:33:26: error: implicit declaration of function ‘ATOMIC_VAR_INIT’; did you mean ‘ATOMIC_FLAG_INIT’? [-Wimplicit-function-declaration]
>    33 | static atomic_int wait = ATOMIC_VAR_INIT(1);
>       |                          ^~~~~~~~~~~~~~~
>       |                          ATOMIC_FLAG_INIT
> udpclash.c:33:26: error: initializer element is not constant
> Could you perhaps use volatile instead?

That works too.  I'll send a new PR tomorrow, its late here.