From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:41940) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1fOFxI-0008Vl-96 for qemu-devel@nongnu.org; Thu, 31 May 2018 01:16:57 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1fOFxH-00067h-Du for qemu-devel@nongnu.org; Thu, 31 May 2018 01:16:56 -0400 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:39864 helo=mx1.redhat.com) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1fOFxH-00067D-9H for qemu-devel@nongnu.org; Thu, 31 May 2018 01:16:55 -0400 From: Peter Xu Date: Thu, 31 May 2018 13:16:38 +0800 Message-Id: <20180531051641.8473-2-peterx@redhat.com> In-Reply-To: <20180531051641.8473-1-peterx@redhat.com> References: <20180531051641.8473-1-peterx@redhat.com> Subject: [Qemu-devel] [RFC v2 1/4] docs: mention shared state protect for OOB List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: =?UTF-8?q?Marc-Andr=C3=A9=20Lureau?= , "Daniel P . Berrange" , Christian Borntraeger , Fam Zheng , Kevin Wolf , Max Reitz , peterx@redhat.com, Eric Auger , Eric Blake , John Snow , Markus Armbruster , Peter Maydell , "Dr . David Alan Gilbert" Out-Of-Band handlers need to protect shared state if there is any. Mention it in the document. Suggested-by: Markus Armbruster Signed-off-by: Peter Xu --- docs/devel/qapi-code-gen.txt | 3 +++ 1 file changed, 3 insertions(+) diff --git a/docs/devel/qapi-code-gen.txt b/docs/devel/qapi-code-gen.txt index b9b6eabd08..aafc15f100 100644 --- a/docs/devel/qapi-code-gen.txt +++ b/docs/devel/qapi-code-gen.txt @@ -680,6 +680,9 @@ OOB command handlers must satisfy the following conditions: - It does not invoke system calls that may block, - It does not access guest RAM that may block when userfaultfd is enabled for postcopy live migration. +- It needs to protect possilbe shared states, since as long as a + command supports Out-Of-Band it means the handler can be run in + parallel with the same handler running in the other thread. If in doubt, do not implement OOB execution support. -- 2.17.0