From patchwork Thu Dec 21 18:43:14 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Bartosz Golaszewski X-Patchwork-Id: 757680 Received: from mail-wm1-f46.google.com (mail-wm1-f46.google.com [209.85.128.46]) (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 A7D2D64A98 for ; Thu, 21 Dec 2023 18:43:22 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=bgdev.pl Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=bgdev.pl Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=bgdev-pl.20230601.gappssmtp.com header.i=@bgdev-pl.20230601.gappssmtp.com header.b="swi0vRw4" Received: by mail-wm1-f46.google.com with SMTP id 5b1f17b1804b1-40d41555f9dso5478215e9.2 for ; Thu, 21 Dec 2023 10:43:22 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bgdev-pl.20230601.gappssmtp.com; s=20230601; t=1703184201; x=1703789001; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:from:to:cc:subject:date:message-id:reply-to; bh=9prIx0x75i3yA19ZQlbyqFnaDcFcCc2+BwEJ02WTlZI=; b=swi0vRw4BYWxBvG4KVUVF+pRpXWJUCHJqYbvM3OhOyroLd9AwqwlkX24Dy3ivMJDjP n9d/2Wk4Ah/R1qiIndPYOaQZZ9ONEpOMiIAHmlpTtFdm+YPntTq5hcbtmP8HoYzlDpGK 2y9qcB66beC2P0fRIunfbNLR/8+GcNQYpt6TMimf0QO4lAkM/ObVfMzhjDZvZxiVr1P7 Rfcaog3tspiwcuECzE5WlnUSlbgivnefmMtGonvaQ60pluwRplin3pSK2WliUsQl68QB 1EFgBiuZOgrmNt/IyOiB7EazmbNMnWKYgWs7ENYR7aR75ePXxUNPtdJv+wDf7HLPf0yQ JHWg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1703184201; x=1703789001; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=9prIx0x75i3yA19ZQlbyqFnaDcFcCc2+BwEJ02WTlZI=; b=KVRgoYDf+WIvruBHHq34ULWTuNBDMKu4zHx4bcqLLtWbeRgObhgXsR2kUVzofKZPBT EuVOK9ph4iBpLJo4W0CpCkQgNqd/Q73vT9uNlkXO1o70fr+w5LNjT4U3vqwZtUk8MsS4 hDbh+n25VPrtjic57uV66ed6xc+2IpwK276QRbtefRUMm/rbgEp4l72GVRI5fLimX+3K pxlCV+V3uSa/HJQgqnZuTa9EzbEiBRIkqjxF3acytp0Ch/T6QIPVsNm9C5pBI6RNqrqB VmwCMU4jkg23Dr4xLq42rdtTR40u957+Rq5HiJ8plwgq5qOE/tlLG2j4HKMKTmgZBXWV JG9Q== X-Gm-Message-State: AOJu0YwLaU1dKyOBNGNPK5SaKpgT6ZqNtY9BMqPueMV0ZC8kfn1aSRAl Hm5Kcq4pBakk+bDR5M1JtlBewT6N5VQC5w== X-Google-Smtp-Source: AGHT+IENwuUJNj2XOxqxCyvHYBTsmnIiHVSSUIF2AWbnh/BX9XLROMGAiuFxSqTFiAO1dLE6ZWcuWg== X-Received: by 2002:a05:600c:4d92:b0:40b:5e59:e9fa with SMTP id v18-20020a05600c4d9200b0040b5e59e9famr78090wmp.153.1703184200735; Thu, 21 Dec 2023 10:43:20 -0800 (PST) Received: from brgl-uxlite.home ([2a01:cb1d:334:ac00:7701:a2c3:cba4:74db]) by smtp.gmail.com with ESMTPSA id t20-20020a05600c199400b0040c42681fcesm4188059wmq.15.2023.12.21.10.43.20 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 21 Dec 2023 10:43:20 -0800 (PST) From: Bartosz Golaszewski To: Linus Walleij , Andy Shevchenko , Kent Gibson Cc: linux-gpio@vger.kernel.org, linux-kernel@vger.kernel.org, Bartosz Golaszewski Subject: [PATCH 0/2] gpiolib: use a read-write semaphore to protect the GPIO device list Date: Thu, 21 Dec 2023 19:43:14 +0100 Message-Id: <20231221184316.24506-1-brgl@bgdev.pl> X-Mailer: git-send-email 2.40.1 Precedence: bulk X-Mailing-List: linux-gpio@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 From: Bartosz Golaszewski I'm still figuring out how to keep GPIO descriptors coherent while (mostly) lockless. In the meantime, I found a potential race-condition during GPIO descriptor lookup and also figured that the correct way to protect the GPIO device list is actually a read-write semaphore as we're not modifying the list very often and readers should be able to iterate over it concurrently. Bartosz Golaszewski (2): gpiolib: replace the GPIO device mutex with a read-write semaphore gpiolib: pin GPIO devices in place during descriptor lookup drivers/gpio/gpiolib-sysfs.c | 2 +- drivers/gpio/gpiolib.c | 58 ++++++++++++++++++++---------------- drivers/gpio/gpiolib.h | 2 +- 3 files changed, 34 insertions(+), 28 deletions(-)