From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtpbguseast3.qq.com (smtpbguseast3.qq.com [54.243.244.52]) (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 6CA713BED2B for ; Fri, 7 Aug 2026 02:01:02 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=54.243.244.52 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786068069; cv=none; b=dGTiDqMa+Mcju9PFriBYZLbIyHn3KKTTdltbqB4HYy94Oj08gDthALYw3t8jWNc1MyFQq2RropBGGMLWhuF06Fsip0+zJwPrXi5M8MZ5MZOS6wbjjAuvI2eQ2/SWWyim9STN0vcRDazTV13VWg5ORHDc8hdVml7cMJwDIzzhoZQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786068069; c=relaxed/simple; bh=luT17W6JwPNzDTantNzwihRXEtF33jeNTIpj44YmkoI=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=ulEsW9zUDU9kqPS7OLnbhQH5KiKJmBgIb+0VdOAddfccRWaLC+wlH6T11d8u9AlfKY1GYgh2eLsR0DEzhqFPO7XzoduH+VIUO7QETkI0pvzi4UbKScO05okuAEJ7jltkfY6VZy4NCU2LtJpMFD/Ge5TVxSzBr32eFdDdaQhv5bw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=uniontech.com; spf=pass smtp.mailfrom=uniontech.com; dkim=pass (1024-bit key) header.d=uniontech.com header.i=@uniontech.com header.b=BkdW5MCO; arc=none smtp.client-ip=54.243.244.52 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=uniontech.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=uniontech.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=uniontech.com header.i=@uniontech.com header.b="BkdW5MCO" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=uniontech.com; s=onoh2408; t=1786067996; bh=4jWCOeKhzKyQSZGatSWRuKZpqMiP/H/phhuCeUn8LfQ=; h=From:To:Subject:Date:Message-Id:MIME-Version; b=BkdW5MCO724CHQwdHafvNqfcdntB95QbLAmi+8TXGs+d3/z/HLrJX9Dm0VJTxRr3Y 7X2UBEwV4WxA0E0PbxPZKUZ+O16au+P8JKbqgEKPYHB8P7r6erslPw/v+RmSo/Iyf9 WgpFDNHatLpDAPOoX0WxWoUSlpwqRz2npSBdz4Vg= X-QQ-mid: zesmtpsz1t1786067991t016aaab1 X-QQ-Originating-IP: gWtj205Dnnn3MeD16Qvc94piaBh9wxJLKisfZk8ybQk= Received: from uniontech.com ( [113.57.152.160]) by bizesmtp.qq.com (ESMTP) with id ; Fri, 07 Aug 2026 09:59:31 +0800 (CST) X-QQ-SSF: 0000000000000000000000000000000 X-QQ-GoodBg: 1 X-BIZMAIL-ID: 3257373749632848062 EX-QQ-RecipientCnt: 13 From: Yichong Chen To: gregkh@linuxfoundation.org Cc: chenyichong@uniontech.com, dakr@kernel.org, djakov@kernel.org, driver-core@lists.linux.dev, linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org, linux-sound@vger.kernel.org, pierre-louis.bossart@linux.dev, quic_mdtipton@quicinc.com, rafael@kernel.org, vkoul@kernel.org, yung-chuan.liao@linux.intel.com Subject: Re: [PATCH v2 1/3] interconnect: debugfs: replace writable string helper Date: Fri, 7 Aug 2026 09:59:30 +0800 Message-Id: <20260807015930.1067612-1-chenyichong@uniontech.com> X-Mailer: git-send-email 2.20.1 In-Reply-To: <2026080632-delighted-bonsai-18b7@gregkh> References: <2026080632-delighted-bonsai-18b7@gregkh> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-QQ-SENDSIZE: 520 Feedback-ID: zesmtpsz:uniontech.com:qybglogicsvrgz:qybglogicsvrgz3a-0 X-QQ-XMAILINFO: NBfkWSW2HKP7k3cNlFgL724HQYJq5qgwP+1xw51PECVFfyRTKMizkqzy HL6a1ouF8eTDTjmWo8TumgFP6aaRAAmKjVzjzbi9SRsY/3w/1xlFdZRhg0Kk7BYaC4MUS6f vgvAWMdFSPE5aJGMAE/XVSvOJEJ597HgjUODRDSHB/It5LXELIgYTjzYpxEUHal+efo+Q9K Fqf1xf0HLKvLmArWpl1+NDYZ7E0cBLEZAX0Vc3gox+x+J7l7AC0Z5dbTpt2q/Qkg/dQuRmh VZLcdZyCyiPyLZ/UJTH3B7fuCkINVtyu8LNEoNgO7vSOeRK6blvCiJAOF12OBCg7DSzKsv0 UUv4pLp9Z6NCCYEtZ1PDVju1ViXFkKzBkZKYrt85OZdpAzg/Ph3MRbZWz3Uh67qhjEIbsP3 TSoF3/PmDFk0pGf8NS3RgF7XoBpM3/gIT+OvX9wCgKR7DVgKpgyp5k85waRZi/YmFNPz604 dKfEC2rBEobjlHeO3ck63ZAJiSiCxg1x76pl+XqNwArXa513MKUOQNAZ81n3nM9DUfHyZLS dhCnorAjU3b1gRbTcIDXWrdPNGFjMxTjdPPcjtzU9x0p1m9FiRgQXdJ3pSXaaJfntHQPdcD I8HW3hVRSMOzApMENgdxlZ73w5GOlItEQz3TZ3/2EYN58+/n2KITt9oSmVRJ5YbUOkgtlUw nY4llbum0wGSPq/hufnHPw97M5zUtN/0TGkWQXijI+byEUKtydGxXox8KdGOdb9a9DpqcvI 9pTcT43/E4AmTt13D53Cvahx2shGzf8d43tiwWu8ibRE+YpgzfZ1LqfqKJyVLOQ2E5OID1m bfQ1NNFh0b+Bz328wQItxKmhBvKFpVjySeZUrdqZ4NvjVzx7nTl+RHGeq0M12PoJXY6c58s 6+rNIyqVrPciNkOXGVunYeOZE0MGmu5tJDowj1oFFEk50Mni9aSzZnKKkRo7ygJknweP/mK Dd4g5eQAKOHPH6bxzUt9D2PKNkOiSg11trf7nr5jkBJhx+J1y9uaRXhx7CsbFbJo7pzPsqK LttWpuuomDi5aqgaDm1W+3eCAErCMsHAN+m0BpVdf6UTG8r/bMlwwx9JAGX/4= X-QQ-XMRINFO: NI4Ajvh11aEjEMj13RCX7UuhPEoou2bs1g== X-QQ-RECHKSPAM: 0 On Thu, Aug 06, 2026 at 11:01:07AM +0200, Greg KH wrote: > On Thu, Aug 06, 2026 at 04:48:52PM +0800, Yichong Chen wrote: > > + mutex_lock(&debugfs_lock); > > + copy = kstrdup(*node ?: "", GFP_KERNEL); > > + mutex_unlock(&debugfs_lock); > > scoped guard? Yes, scoped guard would be cleaner here. I can use it in the next version. > > - src = kstrdup(src, GFP_ATOMIC); > > - dst = kstrdup(dst, GFP_ATOMIC); > > - rcu_read_unlock(); > > + src = kstrdup(src_node, GFP_KERNEL); > > + dst = kstrdup(dst_node, GFP_KERNEL); > > Why is GFP_KERNEL now ok, while GFP_ATOMIC wasn't? Is this the rcu > stuff interacting somehow? Yes. The old code duplicated the strings while still inside the RCU read-side critical section, so it had to use GFP_ATOMIC. After this change, src_node and dst_node are protected by debugfs_lock instead of RCU. The duplication is done while holding that mutex, so the allocation can sleep and GFP_KERNEL should be OK. I will make this clearer in the changelog when sending the next version. Thanks, Yichong