From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-qv1-f45.google.com (mail-qv1-f45.google.com [209.85.219.45]) (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 0AD7C21A4D9 for ; Fri, 25 Oct 2024 20:48:06 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.219.45 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1729889289; cv=none; b=I/55mTef7FG72PaUPtJBtM8wfjQ8We1OHaV4jxyhvbsHM9YQPYdb3EFa6mS0BKkNK4s9uBvnwachzG0EizloSPCM93q91wqjz5mTNtBkmnWNY36oKXoBZEK95dvjIuMEeqATfMuy5QwFtv+Tpj1kudiOt25afQivzAFby9Mce3s= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1729889289; c=relaxed/simple; bh=sValJAQvX5AxaNmTjGZzBJwOh14do82tDXUUsoqP+5c=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=KFYFwhstlaORr72XET+hnKsp6BmyTAD7qpZdGDsVUFLHwA6U48IjAR1nu6rEwWbls3CFc6vOxB4SDiAsAiYNTY9rgFlParDnO7v1vNm1Lhr+X8wDPyZs/fBQIIZGj1FvpjlO8vjTzjm7Krf4Ko1UtyIHikPpGLCPJ9l1cItflIo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=manifault.com; spf=pass smtp.mailfrom=gmail.com; arc=none smtp.client-ip=209.85.219.45 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=manifault.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Received: by mail-qv1-f45.google.com with SMTP id 6a1803df08f44-6cbe90c7c95so15750326d6.1 for ; Fri, 25 Oct 2024 13:48:06 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1729889286; x=1730494086; h=user-agent:in-reply-to:content-disposition:mime-version:references :message-id:subject:cc:to:from:date:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=fRjaD6H/hy34iYED4AXqAZh2gsECEe35fRPiuThhm9o=; b=docYM7ZOG9HtA49nAlbmCQLxJi5NW4+FLqm3Ze/d17I2rBTdixm9VI6iRLbaHhUe6l mzovosEValFU8kLiOLnAdfpWz1G1bN/SewFPqGBtcBVruDz88x03TRxROzMvgWH3X0yf UUIgv6JJR4TS3kt4eifkNQvLZGshbcMEA7kVwgFDbhtZTi2CK3T3EOKmd4VOYXn/HVoj JMDdTYICQ+RVKJ2xQ517kKtZRvDObQSP4Eb8BMME0gdM1tLg9UodPs1B2ejl0MoQwu22 /3friFWOd7Dzf5op5+govSuQ4LhZ31YQmCgI8cOoXvoWQaL9B+x+cNJWWlOVknJfUOtB WPqA== X-Forwarded-Encrypted: i=1; AJvYcCUoZs6KfPXVZOJdF717CJmp79MDAD5LKpnTeRXEITk3W1ZroBK9M0vIGqZnv3Q2tflX55BjFFR4eweKo8A=@vger.kernel.org X-Gm-Message-State: AOJu0Yx2sF0I9EsCwM1lhx0ygvaYFvkelSjdX+eAFlM+fnn3Z7Kq7pwv qqUS06cpGm/CV6GuHWSrH0v3ln5Dpc5OEscj34kMTBH0/pvmq2tu X-Google-Smtp-Source: AGHT+IECIkXB+fdK0+u+4To88RYENspNPtL18iOtAw7uiVxLvIgBzAPSuSp5uvXiZU5L7KzQ/JS0cg== X-Received: by 2002:a05:6214:4305:b0:6cc:37cf:5dc8 with SMTP id 6a1803df08f44-6d1856f27f3mr8239636d6.21.1729889285965; Fri, 25 Oct 2024 13:48:05 -0700 (PDT) Received: from maniforge (c-76-141-129-107.hsd1.il.comcast.net. [76.141.129.107]) by smtp.gmail.com with ESMTPSA id 6a1803df08f44-6d179a2d466sm9124716d6.115.2024.10.25.13.48.04 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 25 Oct 2024 13:48:05 -0700 (PDT) Date: Fri, 25 Oct 2024 15:48:02 -0500 From: David Vernet To: Tejun Heo Cc: sched-ext@meta.com, kernel-team@meta.com, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2] scx: Fix raciness in scx_ops_bypass() Message-ID: <20241025204802.GA24112@maniforge> References: <20241025203929.22839-1-void@manifault.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="zhwkI6gVP57BwS0T" Content-Disposition: inline In-Reply-To: User-Agent: Mutt/2.2.13 (00d56288) (2024-03-09) --zhwkI6gVP57BwS0T Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Fri, Oct 25, 2024 at 10:43:53AM -1000, Tejun Heo wrote: > Hello, >=20 > This looks great overall. One nit below. >=20 > On Fri, Oct 25, 2024 at 03:39:29PM -0500, David Vernet wrote: > ... > > static void scx_ops_bypass(bool bypass) > > { > > - int depth, cpu; > > + int cpu; > > + unsigned long flags; > > =20 > > + raw_spin_lock_irqsave(&__scx_ops_bypass_lock, flags); > > if (bypass) { > > - depth =3D atomic_inc_return(&scx_ops_bypass_depth); > > - WARN_ON_ONCE(depth <=3D 0); > > - if (depth !=3D 1) > > - return; > > + scx_ops_bypass_depth++; > > + WARN_ON_ONCE(scx_ops_bypass_depth <=3D 0); > > + if (scx_ops_bypass_depth !=3D 1) > > + goto unlock; > > } else { > > - depth =3D atomic_dec_return(&scx_ops_bypass_depth); > > - WARN_ON_ONCE(depth < 0); > > - if (depth !=3D 0) > > - return; > > + scx_ops_bypass_depth--; > > + WARN_ON_ONCE(scx_ops_bypass_depth < 0); > > + if (scx_ops_bypass_depth !=3D 0) > > + goto unlock; >=20 > Now that we know irq is disabled in the body, can you also please change > rq_lock_irqsave() to rq_lock? Ah good point, will send v3 shortly. >=20 > Thanks. >=20 > --=20 > tejun --zhwkI6gVP57BwS0T Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iHUEARYKAB0WIQRBxU1So5MTLwphjdFZ5LhpZcTzZAUCZxwEAgAKCRBZ5LhpZcTz ZI94AQDAUzuRMJUKoB6XqP0d7PIJ5qNcsWW6A16YJ9X/fr2x9AD/WGAFDukRUWPd 5gNg1vqfuseuFWKtUaW4OdY6BeyzUQo= =qg65 -----END PGP SIGNATURE----- --zhwkI6gVP57BwS0T--