From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pf1-f177.google.com (mail-pf1-f177.google.com [209.85.210.177]) (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 F300A15FA9F for ; Thu, 18 Apr 2024 15:56:17 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.210.177 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1713455779; cv=none; b=ayoHYOkCO2qLeB0OvQlrD8Ge0gLnxnmB76PSWDYZo6kdJaAC+qep1K+RESf+fzXLHbxiArHzznCYRqjQVYDEgQzK2B5GQdJiBN7EXTN4Nmvxp3yxXw475fzPdqYqqGmv/N2C1lRlhYUeZs7ElNzX+GkZaPXTCnqdZlutyyEUEQI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1713455779; c=relaxed/simple; bh=mDRjfBiPjMWn261FMr3b8oWZieXKRIxWEC729h8K7sg=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=DL9j9K7udsxTPWnrKRLK8gV67cTON8r/P7Vi1FCvKO3OXc1rkpP5U6RWXCaSs0KsCUzGVm97TEwJxdVhtYRkLe1iAKWuHCAbowhHKYz3Z/a9N6zL2YSz/xM8Wt7P/bbY0nKuF65KZm+QJGXJSph+sZCUlAFPYasI2tKVCSGxXvA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=OTxcocgG; arc=none smtp.client-ip=209.85.210.177 Authentication-Results: smtp.subspace.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="OTxcocgG" Received: by mail-pf1-f177.google.com with SMTP id d2e1a72fcca58-6ed01c63657so988369b3a.2 for ; Thu, 18 Apr 2024 08:56:17 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1713455777; x=1714060577; darn=vger.kernel.org; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:sender:from:to:cc:subject:date:message-id :reply-to; bh=GnRoVABkMpTwTwJRlnT/WRT83zNRcjsjqktPei1RqZc=; b=OTxcocgG+gc/7Br+1KJeAFOHbYwSFqLV0joIJBS/GUX2vZVMYpSetfcLwnw3XGMsu2 lrxWZUV6tXbNTpig1y1H1ukh81KJxdiDYqbEfPttYwRamQ/295ZedcoLg60ukF83F8BZ QQNlmS18OpWYDJE+tc0o9eNdEXLfHW8/7uAtlBuMZwduvhTOdIeHVGwzYA5/p1uq4529 R9vU9fiAt9eIVmqTFCrLMeOtS32rf2EM8i7+aaRqUQFHPyKVdWD6jPvAWdBH198uSr7Z sfscgwcENVmsEFNgWYOcOOHUV4ZiN9mYXDy7AtY+J9xygdVzdLQAao1ReP6c4W+LYJHt eyUw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1713455777; x=1714060577; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:sender:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=GnRoVABkMpTwTwJRlnT/WRT83zNRcjsjqktPei1RqZc=; b=OjmuevfwkrVI+valAm7iiQEIBy/pQHt5oJi7o9oncRnprFtFLITCpMMo7WTYsVxmtK cMEMLosYeHY7lM08ANRefgiCVLRZa8kahPEpC5hiVZuspJX8ylLTm7L0ShDGzu7xQj7j GKoXhdPDtJ1CSAtBuUvLUdPZU17zy4nsXXSaQ8PQWiAlvSQIbBILPfSTWNHor0Uoddoi atIZLMHeMFZhbJ8AHJoJB2UiLtjYg1rz3ikPX8x2zmHNnq4vXiRWbGPdKIvbd/T69khr tNsHaeQaTb++QZK9XwphVmDThVbCggz3Za4l8lUwrqpVclgjot97L81mNC8dujf5zEH9 09Ag== X-Forwarded-Encrypted: i=1; AJvYcCWA+KooQbGnVF/BJXNE0QefDxU1z+7BZ+tzmh6t4qOlXV/8s3PsHVwDkvnjhSmN6EuTvNgaBNCiwLcq9kjTLSQLpFaHMilTMKMKu3D+ X-Gm-Message-State: AOJu0YzE5uSCz0d6/94kKxvDvj+xgExEj1/hiEjpFNRHgCcWpLZX2wSH G+a1gK8vsViesgzt41E0Fb2r75ntybUVUjhWgXZQw76hMJCVIXvG X-Google-Smtp-Source: AGHT+IGXisnKjI71uANED1CP/KTHgH+Gcr2xad6cRyLgWvCNRvdOFFUmfzdZFprOYudDsZZZcmmqGA== X-Received: by 2002:a05:6a00:3d07:b0:6ed:41f3:cd06 with SMTP id lo7-20020a056a003d0700b006ed41f3cd06mr3912520pfb.7.1713455777244; Thu, 18 Apr 2024 08:56:17 -0700 (PDT) Received: from localhost ([2620:10d:c090:400::5:6f51]) by smtp.gmail.com with ESMTPSA id x12-20020a056a000bcc00b006e580678dfbsm1639967pfu.193.2024.04.18.08.56.16 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 18 Apr 2024 08:56:16 -0700 (PDT) Sender: Tejun Heo Date: Thu, 18 Apr 2024 05:56:15 -1000 From: Tejun Heo To: Sven Schnelle Cc: Lai Jiangshan , linux-kernel@vger.kernel.org Subject: Re: [PATCH] workqueue: fix selection of wake_cpu in kick_pool() Message-ID: References: <20240415053550.538722-1-svens@linux.ibm.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Thu, Apr 18, 2024 at 07:54:37AM +0200, Sven Schnelle wrote: > Tejun Heo writes: > > > Hello, > > > > On Wed, Apr 17, 2024 at 05:36:38PM +0200, Sven Schnelle wrote: > >> > This generally seems like a good idea but isn't this still racy? The CPU may > >> > go down between setting p->wake_cpu and wake_up_process(). > >> > >> Don't know without reading the source, but how does this code normally > >> protect against that? > > > > Probably by wrapping determining the wake_cpu and the wake_up inside > > cpu_read_lock() section. > > Thanks. Should i send a v2 and incorporate your additional changes or do > you want to do that? Yes, please send a v2. Thanks. -- tejun