From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:50946) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1fJcWK-00063c-7y for qemu-devel@nongnu.org; Fri, 18 May 2018 06:21:57 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1fJcWH-0006I1-2b for qemu-devel@nongnu.org; Fri, 18 May 2018 06:21:56 -0400 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:41550 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 1fJcWG-0006Hr-Ul for qemu-devel@nongnu.org; Fri, 18 May 2018 06:21:53 -0400 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.rdu2.redhat.com [10.11.54.5]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 7E780BB41A for ; Fri, 18 May 2018 10:21:52 +0000 (UTC) Date: Fri, 18 May 2018 18:21:43 +0800 From: Peter Xu Message-ID: <20180518102143.GO2569@xz-mi> References: <20180509041734.14135-1-peterx@redhat.com> <20180509041734.14135-4-peterx@redhat.com> <87zi0ylaab.fsf@dusky.pond.sub.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <87zi0ylaab.fsf@dusky.pond.sub.org> Subject: Re: [Qemu-devel] [PATCH v5 3/4] monitor: more comments on lock-free fleids/funcs List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Markus Armbruster Cc: qemu-devel@nongnu.org, "Dr . David Alan Gilbert" , Stefan Hajnoczi , =?utf-8?Q?Marc-Andr=C3=A9?= Lureau On Thu, May 17, 2018 at 02:46:36PM +0200, Markus Armbruster wrote: > Peter Xu writes: > > > Add some explicit comment for both Readline and cpu_set/cpu_get helpers > > that they do not need the mon_lock protection. > > Appreciated! > > > Signed-off-by: Peter Xu > > --- > > monitor.c | 5 +++-- > > 1 file changed, 3 insertions(+), 2 deletions(-) > > > > diff --git a/monitor.c b/monitor.c > > index d6c3c08932..ae5bca9d7c 100644 > > --- a/monitor.c > > +++ b/monitor.c > > @@ -207,7 +207,7 @@ struct Monitor { > > int suspend_cnt; /* Needs to be accessed atomically */ > > bool skip_flush; > > bool use_io_thr; > > - ReadLineState *rs; > > + ReadLineState *rs; /* Only used in parser, so no lock needed. */ > > Pardon the ignorant question: why does "only used in parser" imply "no > lock needed"? Since even if the monitors can be run in multiple threads now, the monitor parser of a specific Monitor will still only be run in either the main thread or the monitor iothread. My fault to be unclear on the comment. Maybe this one is better: It is only used in parser, and the parser of a monitor will only be run either in main thread or monitor IOThread but never both, so no lock is needed when accessing ReadLineState. > > > MonitorQMP qmp; > > gchar *mon_cpu_path; > > BlockCompletionFunc *password_completion_cb; > > @@ -1313,7 +1313,7 @@ void qmp_qmp_capabilities(bool has_enable, QMPCapabilityList *enable, > > cur_mon->qmp.commands = &qmp_commands; > > } > > > > -/* set the current CPU defined by the user */ > > +/* set the current CPU defined by the user. BQL needed. */ > > It's okay to start a comment containing a phrase with a lower case > letter, but you're turning this one into two sentences, and sentences > start in upper case. Can touch up on commit. > > "BQL needed" is okay, just a bit terse; I'd write "Caller must hold > BQL". Could change that, too. I'll do that. > > > int monitor_set_cpu(int cpu_index) > > { > > CPUState *cpu; > > @@ -1327,6 +1327,7 @@ int monitor_set_cpu(int cpu_index) > > return 0; > > } > > > > +/* BQL neeeded. */ > > Likewise. Will do. Thanks, -- Peter Xu