From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=198.175.65.17 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1793890395; b=WnpKyaQBt8qd3Oht1SdE2Cyj5Tf6FW92u/fEZvZtDlS6umDt5NQU2q4GNMzlVqxQb17K xJZ8ejpYvexf1Uiqp87AVfd8G2AUxzqN/+ICFWUSnrUW7Vzf9aby07aWJ8FZKqBCD3K1g KQB17+ydxPlaeOiadABFXjuGc+S54o7D6uOpFp72WzoiolpTceZw8tORh9fE+TCbNi3fm SMMODQPleY36r9+GaOho5IyCtMBxHMU24dQyq1mftvBDtCSoaZYWzsz3hrhJIu10ERq5U Ea7ktwNPf5FcTwz+A3oyFcXlT+u+C1g+a7zsBJYK8xoxJsQQUxzfeVw4CB5l1CmB/AA== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793890395; h=DMARC-Filter:DKIM-Signature:X-CSE-ConnectionGUID:X-CSE-MsgGUID: X-IronPort-AV:X-IronPort-AV:Received:X-CSE-ConnectionGUID: X-CSE-MsgGUID:X-ExtLoop1:X-IronPort-AV:Received:Date:From:To:Cc: Subject:Message-ID:References:MIME-Version:Content-Type: Content-Disposition:In-Reply-To:Organization; bh=O5hH3VfyULzh0DN1X+8MY3AyC3KeT6fXdQrbN3Uw/b8=; b=ystrnTyDRGsr+BLrPH8hjRRsrpywfVWThl84EulhQM4n4rOvHep/+qF3nsEEYMVIFGBU x53kqC3G6qN8vZWUCutJ5RZnaLQhZb/Kkz8rwC4NcbOVQd+GK2B4l2YuwFSCspqRiSFq7 1U4VL4g0+MIrBFsa5SNL+AIsnN7cvruOwl78e0r1NWbSD79BKP3i5iV7msgnQeEIdkfDk 7wQUi1EG1+a+A4In5bdzMmJMaiKS8IlQZndrG8E0Vuh7C5GY6Ll2a+P4UjWYCbK63iWye lR1/q4FNCwpjCYnMgkILiGkxGDVL3PiHdYgt0w5bY7AxN5o0dgaaFN5EJG+eS8E6uCA== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass header.from=linux.intel.com; spf=pass smtp.mailfrom=linux.intel.com; dkim=pass header.d=intel.com header.i=@intel.com header.a=rsa-sha256 header.s=Intel header.b=XWivxVJO; arc=none smtp.remote-ip=198.175.65.17 Received: from mgamail.intel.com (mgamail.intel.com [198.175.65.17]) (using TLSv1.2 with cipher ECDHE-ECDSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id A067C606A31B; Thu, 5 Nov 2026 14:53:14 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.2 smtp.subspace.kernel.org A067C606A31B Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.intel.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.intel.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=intel.com header.i=@intel.com header.a=rsa-sha256 header.s=Intel header.b=XWivxVJO DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1793890395; x=1825426395; h=date:from:to:cc:subject:message-id:references: mime-version:in-reply-to; bh=QMqDS3LOi71OKtkWUaXE5hLFpSteQzGSoTt3Q02rIfA=; b=XWivxVJOwVoc2+I6t1A6j2MlFlzlxhhC0UQ6d+KOrm+VM0md31AON8im uYlDLSzvXnDh2fRnDCZohZz3JfjDyeCv7aSkP8M8M5DL0aLRaqGBBlNqI 8Xbz/jG9rqgQvPuj+jU0kMzwEu5pvFfUBh6EZrJSGOIjHnuDf8WTaq8vJ EdLkWxBAc475kRdQr2KrOXw205yTUUajzxskPL8r0jmGNEuKeQGt1fNiu M9He3oLKDaxjVzsAGqCfEOPkKUbTnMju3r65eSXJT2kUbim/b6zTbkACV 4VJuDBzCt0r/Ei1ao2hibuNY3kMmVP4YY0r2pq7iQAQGJ5R1ApBWBfpJr w==; X-CSE-ConnectionGUID: z2RzWl+yTBCSOf9gonjNKw== X-CSE-MsgGUID: Dgqn15+FTAOfGedup2y+cg== X-IronPort-AV: E=McAfee;i="6800,10657,11957"; a="2705839" X-IronPort-AV: E=Sophos;i="6.27,197,1787036400"; d="scan'208";a="2705839" Received: from fmviesa001.fm.intel.com ([10.60.135.141]) by orvoesa109.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 05 Nov 2026 06:53:14 -0800 X-CSE-ConnectionGUID: cEb3y3+mTju9ELfFRG3m4A== X-CSE-MsgGUID: YPcdfl0VTOu5ZX8ya3qKig== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.27,197,1787036400"; d="scan'208";a="7371167" Received: from amilburn-desk.amilburn-desk (HELO localhost) ([10.245.244.144]) by smtpauth.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 05 Nov 2026 06:53:12 -0800 Date: Thu, 5 Nov 2026 16:53:10 +0200 From: Andy Shevchenko To: Bartosz Golaszewski Cc: Linus Walleij , Bartosz Golaszewski , linux-gpio@vger.kernel.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: Re: [PATCH] gpiolib: synchronize updates of descriptor labels Message-ID: References: <20261105-gpiolib-set-desc-label-corruption-v1-1-fa84726ceac0@oss.qualcomm.com> X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20261105-gpiolib-set-desc-label-corruption-v1-1-fa84726ceac0@oss.qualcomm.com> Organization: Intel Finland Oy - BIC 0357606-4 - c/o Alberga Business Park, 6 krs, Bertel Jungin Aukio 5, 02600 Espoo On Thu, Nov 05, 2026 at 02:23:45PM +0100, Bartosz Golaszewski wrote: > desc_set_label() swaps desc->label with rcu_replace_pointer() but > without any synchronization of concurrent updates. The swap is a plain > read + write: two threads can observe the same old label and then call s/call// > call_scru() on the same SRCU head corrupting the state of the chain. > > Add a spinlock to struct gpio_device - we're using a single spinlock for > all descriptors as using a per-descriptor lock would unnecessarily bloat > the size of the desc array with very little chance and no consequences of > contention - and use it to serialize the pointer update. ... > - old = rcu_replace_pointer(desc->label, new, 1); > - if (old) > - call_srcu(&desc->gdev->desc_srcu, &old->rh, desc_free_label); > + scoped_guard(spinlock, &desc->gdev->desc_lock) { > + old = rcu_replace_pointer(desc->label, new, > + lockdep_is_held(&desc->gdev->desc_lock)); Can lockdep_is_held() return anything except LOCK_STATE_HELD here? Or is it checked outside of this scoped_guard()? > + if (old) > + call_srcu(&desc->gdev->desc_srcu, &old->rh, desc_free_label); > + } -- With Best Regards, Andy Shevchenko