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 7814C27182B for ; Wed, 12 Feb 2025 00:52:55 +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=1739321575; cv=none; b=bmPC1S+snDyMrY+gCHwjzxoijcdUtamapSWnvHKwBvwu1GNDzDgNzZVgOfFujkkYp1UzRUBa4GIcfVQEL1Wbq9jw6GKU1fybqbF/ChJlKK7+0ozUUUt5G5fWTtoB3iua6Bjui792SvVSQKe6SL7m6eX+vBfQip7BxKwWGLDDTSI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1739321575; c=relaxed/simple; bh=KroWA/EUy4urQEkNQ7tnbRPRUl5IBNSI/vXekvZfy2M=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=Mc3Vsdv0CWU3HL/fOXbUKbbI3IgD4Z2Ig2KMZQqvoIdIBPSHSIGzDi278CoT0xGus9IMgd2zkwEfuykdjiG1TtbifoMQge6KWw0KyAqOLOo9tmgEc31Rmp6ck3H/jL6S+opaFtaRk5pcBMyxxgC745XPUxX3uHYSM/jpkPpJ/Qs= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=eX9PiYof; 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="eX9PiYof" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9AD75C4CEE2; Wed, 12 Feb 2025 00:52:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1739321574; bh=KroWA/EUy4urQEkNQ7tnbRPRUl5IBNSI/vXekvZfy2M=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=eX9PiYofQs+Awgr2SgPBOdFtriO25JW8gGLAfEYGYd/xhbXnC+eJ9Bkc+VuuaYaD9 tmPTrSrf8b+nDEeCl47Rf2uQKgJ2zI4yLwicbVPsdYUUzULgP2Ju4C59IOlkJfvFR9 TSuDxtUDWyO+j+VpBX3YY/VCnCGpGvzz/1VRVWE6CYIliXMn7bYvosJqezWz/TQjsi mqsLdfdVM3k/1ltdHm4Qli36/llKkqTEUbdHAjHrUndWHka0thB8sBS5zIS6sWyuZx s3mF3XuQ/jhRqpjZCGaOMnZJJPasWF9rWlL5verRePeJokNl+aW5QLE8x8WIQZdTkO 1FqL1o085KtYw== Date: Tue, 11 Feb 2025 16:52:53 -0800 From: Josh Poimboeuf To: Yafang Shao Cc: jikos@kernel.org, mbenes@suse.cz, pmladek@suse.com, joe.lawrence@redhat.com, live-patching@vger.kernel.org Subject: Re: [PATCH 3/3] livepatch: Avoid potential RCU stalls in klp transition Message-ID: <20250212005253.4d6wru5lsrvxch45@jpoimboe> References: <20250211062437.46811-1-laoar.shao@gmail.com> <20250211062437.46811-4-laoar.shao@gmail.com> Precedence: bulk X-Mailing-List: live-patching@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20250211062437.46811-4-laoar.shao@gmail.com> On Tue, Feb 11, 2025 at 02:24:37PM +0800, Yafang Shao wrote: > +++ b/kernel/livepatch/transition.c > @@ -491,9 +491,18 @@ void klp_try_complete_transition(void) > complete = false; > break; > } > + > + /* Avoid potential RCU stalls */ > + if (need_resched()) { > + complete = false; > + break; > + } > } > read_unlock(&tasklist_lock); > > + /* The above operation might be expensive. */ > + cond_resched(); > + This is also nasty, yet another reason to use rcu_read_lock() if we can. Also, with the new lazy preemption model, I believe cond_resched() is pretty much deprecated. Also, for future patch sets, please also add lkml to cc. Thanks. -- Josh