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Mon, 17 Sep 2018 19:58:55 +0000 Received: from userv0122.oracle.com (userv0122.oracle.com [156.151.31.75]) by userv0021.oracle.com (8.14.4/8.14.4) with ESMTP id w8HJwnkC012115 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Mon, 17 Sep 2018 19:58:49 GMT Received: from abhmp0014.oracle.com (abhmp0014.oracle.com [141.146.116.20]) by userv0122.oracle.com (8.14.4/8.14.4) with ESMTP id w8HJwm4B002541; Mon, 17 Sep 2018 19:58:48 GMT Received: from dhcp-burlington7-2nd-B-east-10-152-55-162.usdhcp.oraclecorp.com (/10.152.32.65) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Mon, 17 Sep 2018 12:58:48 -0700 Subject: Re: [Xen-devel] [PATCH 2/6] xenbus: implement the xenwatch multithreading framework To: Dongli Zhang , xen-devel@lists.xenproject.org, linux-kernel@vger.kernel.org Cc: jgross@suse.com, wei.liu2@citrix.com, konrad.wilk@oracle.com, srinivas.eeda@oracle.com, paul.durrant@citrix.com, roger.pau@citrix.com References: <1536910456-13337-1-git-send-email-dongli.zhang@oracle.com> <1536910456-13337-3-git-send-email-dongli.zhang@oracle.com> <1443a6e8-0a94-6081-b1c6-1f426bbaea38@oracle.com> From: Boris Ostrovsky Openpgp: preference=signencrypt Autocrypt: addr=boris.ostrovsky@oracle.com; 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Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.0 MIME-Version: 1.0 In-Reply-To: <1443a6e8-0a94-6081-b1c6-1f426bbaea38@oracle.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Content-Language: en-US X-Proofpoint-Virus-Version: vendor=nai engine=5900 definitions=9019 signatures=668708 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 suspectscore=0 malwarescore=0 phishscore=0 bulkscore=0 spamscore=0 mlxscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1807170000 definitions=main-1809170197 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 9/16/18 9:48 PM, Dongli Zhang wrote: > Hi Boris, > > On 09/17/2018 05:20 AM, Boris Ostrovsky wrote: >> >> On 9/14/18 3:34 AM, Dongli Zhang wrote: >>> + >>> +/* Running in the context of default xenwatch kthread. */ >>> +void mtwatch_create_domain(domid_t domid) >>> +{ >>> + struct mtwatch_domain *domain; >>> + >>> + if (!domid) { >>> + pr_err("Default xenwatch thread is for dom0\n"); >>> + return; >>> + } >>> + >>> + spin_lock(&mtwatch_info->domain_lock); >>> + >>> + domain = mtwatch_find_domain(domid); >>> + if (domain) { >>> + atomic_inc(&domain->refcnt); >>> + spin_unlock(&mtwatch_info->domain_lock); >>> + return; >>> + } >>> + >>> + domain = kzalloc(sizeof(*domain), GFP_ATOMIC); >> Is there a reason (besides this being done under spinlock) for using GFP_ATOMIC? >> If domain_lock is the only reason I'd probably drop the lock and do GFP_KERNEL. > spin_lock is the reason. > > Would you like to switch to a mutex here? I'd use mutex. -boris