From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 3F2A51E8348; Tue, 8 Apr 2025 19:03:19 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1744139000; cv=none; b=daCmE0sVdDX+eQmS6fsTLgTrP4Ip9q6WVVWpZlMuciXDDjhBpoXO1anZIdrkORTyhkX8stt6uM8nmzzc/jUGoq8tu81euHCyoxjyRhRVo7IG66jHWoacJ5MkEHei3aJlZa9J2Vcxb2J3zZ4sKe2a0yxOHsPAfxSBS+fXl7V+YIo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1744139000; c=relaxed/simple; bh=EARKT6yocmAnZReK9tqnX7V8Nt3uW8Qi9d8HfF7ZBIc=; h=Date:From:To:Cc:Subject:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=IxyggzWqJ83UIZVSncoBpOGjQyZ/Ab8ASl3yzwuToa/UB0QPBJcp3Vs9Di0AB3vse05DX0MIyfXLdCJBt7DJr+6kioPQrqj8QvcyUcDY3UK0O0eps9OfWA4s3pIOTRnFEqaYJ7yG+HCO89H4dN7YQPeNe56144jMq8LxZ4Qx3U0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=QgzbA7j2; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="QgzbA7j2" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 25DEAC4CEE5; Tue, 8 Apr 2025 19:03:19 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1744138999; bh=EARKT6yocmAnZReK9tqnX7V8Nt3uW8Qi9d8HfF7ZBIc=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=QgzbA7j2lLvOFPCnvGx0gUDpMilm+wUBS+wydoweKRrbUNyJND9JIA2BnY8WbOP4Q gCschZ3zZWrxxq92rKWwHsb6Au5m28T1hvK1J+7YUPAem5ChwnK00OhB/2ARcpEYGY 5jBejeZJDT3hHEjrOz2R1qrlQLztAIqvhNv9U1wgRTN/KFJwXewLP595EXnXQZRikx J9HNQu8gU82pzmzhEYIYf31wgv1BlKZQwzPxLhykp+1uwo0b991bQtU8C8irCcfRlu 46EM5E76hGYjp+y2kZfV338kCYp9DxwiKZmpRIM8JdEdwWe8bmNDi3UwuDP4SzSqQ5 7VioB9FTcWMDg== Date: Tue, 8 Apr 2025 12:03:18 -0700 From: Jakub Kicinski To: Matthieu Baerts Cc: Stanislav Fomichev , netdev@vger.kernel.org, davem@davemloft.net, edumazet@google.com, pabeni@redhat.com, paulmck@kernel.org, joel@joelfernandes.org, steven.price@arm.com, akpm@linux-foundation.org, anshuman.khandual@arm.com, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org Subject: Re: [PATCH net-next] configs/debug: run and debug PREEMPT Message-ID: <20250408120318.65125876@kernel.org> In-Reply-To: References: <20250402172305.1775226-1-sdf@fomichev.me> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Tue, 8 Apr 2025 20:18:26 +0200 Matthieu Baerts wrote: > On 02/04/2025 19:23, Stanislav Fomichev wrote: > > Recent change [0] resulted in a "BUG: using __this_cpu_read() in > > preemptible" splat [1]. PREEMPT kernels have additional requirements > > on what can and can not run with/without preemption enabled. > > Expose those constrains in the debug kernels. > > Good idea to suggest this to find more bugs! > > I did some quick tests on my side with our CI, and the MPTCP selftests > seem to take a bit more time, but without impacting the results. > Hopefully, there will be no impact in slower/busy environments :) What kind of slow down do you see? I think we get up to 50% more time spent in the longer tests. Not sure how bad is too bad.. I'm leaning towards applying this to net-next and we can see if people running on linux-next complain? Let me CC kselftests, patch in question: https://lore.kernel.org/all/20250402172305.1775226-1-sdf@fomichev.me/