From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from va-1-113.ptr.blmpb.com (va-1-113.ptr.blmpb.com [209.127.230.113]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 82736481DD for ; Thu, 19 Mar 2026 02:30:37 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.127.230.113 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773887439; cv=none; b=WA+7BvAlx7Go9qRMXW7jJev6qgzNHX/J++/20x+ou506yest52OoauzFisY29PvT5SiMy5tTCxgoxNOMG2WrP4EaKFp1d1Cggc9Y5uMCv6rnAqQ5a7pl4zveXlIMjzH61xMjMtGb+4ys16c+XsRTx7gXNz1Zt/kqmsLS2Q4rwhE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773887439; c=relaxed/simple; bh=wBLxBSH+eFxUQ/ZZ6PgQ0lZbstUWuuyvqKuNhsTCPYA=; h=Message-Id:Content-Type:To:Cc:Subject:In-Reply-To:Date: Mime-Version:References:From; b=LkjPlegAsfn8gNTLix4tdGuE2ztJyq2vafBdW49PxnM3Z9WiTC4Bso483MV45b2bNS5qKbEFMRPLv+XNoleD6Y1lVaUBmvQwyWQ41BHWUcyPo+NKuWGiUXSS9LNCWBoxizVXirLBRJkRsyh7Ek7LbeI7iNsGvrkEhT7oEYEvrWw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=bytedance.com; spf=pass smtp.mailfrom=bytedance.com; dkim=pass (2048-bit key) header.d=bytedance.com header.i=@bytedance.com header.b=BqNiOsxU; arc=none smtp.client-ip=209.127.230.113 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=bytedance.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=bytedance.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=bytedance.com header.i=@bytedance.com header.b="BqNiOsxU" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; s=2212171451; d=bytedance.com; t=1773887432; h=from:subject: mime-version:from:date:message-id:subject:to:cc:reply-to:content-type: mime-version:in-reply-to:message-id; bh=6ccLRc5nxRmJkK5qmAnUd7y6s1mOrsBKldmBIMLui/0=; b=BqNiOsxUV7GOIaVDxlP2gihwZ2156faIPXqLcr7h2BMka+Yzjf49JUkcLIRczvC5zNqDut TxpqUEutjjc6ZMidgoNC0WoRBZg3HA1nj+087xq96B+abYXxOV2u+d5orQ3jp55VdvRYvw KW6u/lhzqCzybW8SPKVGILMXoM586RuDHS9lZ+cUdMGJ69t+SY4q3YckBmJT5K9m95R+SK X1PzgG3dLOVs3v7dMKCsz4NAhmkYTz+W+EMFwFwMX6UC5keAFTLBHz8F+6Mqs428RHhvPh NTqHowqujzsXjAGX8yyKKxa5snZ3yM3U6Y13b7mchIT2PiD8TATtkkbnNNgvZg== Message-Id: Content-Type: text/plain; charset=UTF-8 To: "Steven Rostedt" Cc: , , , , , , , , , , , Subject: Re: [PATCH v3 02/12] smp: Enable preemption early in smp_call_function_single In-Reply-To: <20260318101442.371c69ae@gandalf.local.home> Date: Thu, 19 Mar 2026 10:30:14 +0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 X-Original-From: Chuyi Zhou References: <20260318045638.1572777-1-zhouchuyi@bytedance.com> <20260318045638.1572777-3-zhouchuyi@bytedance.com> <20260318101442.371c69ae@gandalf.local.home> User-Agent: Mozilla Thunderbird X-Lms-Return-Path: From: "Chuyi Zhou" Content-Transfer-Encoding: quoted-printable Hi Steve, =E5=9C=A8 2026/3/18 22:14, Steven Rostedt =E5=86=99=E9=81=93: > On Wed, 18 Mar 2026 12:56:28 +0800 > "Chuyi Zhou" wrote: >=20 >> diff --git a/kernel/smp.c b/kernel/smp.c >> index fc1f7a964616..b603d4229f95 100644 >> --- a/kernel/smp.c >> +++ b/kernel/smp.c >> @@ -685,11 +685,16 @@ int smp_call_function_single(int cpu, smp_call_fun= c_t func, void *info, >> =20 >> err =3D generic_exec_single(cpu, csd); >> =20 >> + /* >> + * @csd is stack-allocated when @wait is true. No concurrent access >> + * except from the IPI completion path, so we can re-enable preemption >> + * early to reduce latency. >> + */ >=20 > Thanks for the comment. I walked through the code and this looks fine to = me. >=20 >> + put_cpu(); >> + >> if (wait) >> csd_lock_wait(csd); >> =20 >> - put_cpu(); >> - >> return err; >=20 > Reviewed-by: Steven Rostedt (Google) >=20 Thanks! > -- Steve