From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:47143) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1fTdlw-0008TF-96 for qemu-devel@nongnu.org; Thu, 14 Jun 2018 21:43:29 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1fTdlt-0003kh-5S for qemu-devel@nongnu.org; Thu, 14 Jun 2018 21:43:28 -0400 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:59420 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 1fTdlt-0003k8-0a for qemu-devel@nongnu.org; Thu, 14 Jun 2018 21:43:25 -0400 From: Peter Xu Date: Fri, 15 Jun 2018 09:42:47 +0800 Message-Id: <20180615014249.22730-5-peterx@redhat.com> In-Reply-To: <20180615014249.22730-1-peterx@redhat.com> References: <20180615014249.22730-1-peterx@redhat.com> Subject: [Qemu-devel] [PATCH v3 4/6] 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 1366228b2a..bee9de35df 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 any shared state, 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. -- 2.17.1