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Wed, 2 Jun 2021 10:06:58 -0400 (EDT) Received: from localhost (localhost [127.0.0.1]) by mail.efficios.com (Postfix) with ESMTP id 84F0C302AEF; Wed, 2 Jun 2021 10:06:58 -0400 (EDT) DKIM-Filter: OpenDKIM Filter v2.10.3 mail.efficios.com 84F0C302AEF X-Virus-Scanned: amavisd-new at efficios.com Received: from mail.efficios.com ([127.0.0.1]) by localhost (mail03.efficios.com [127.0.0.1]) (amavisd-new, port 10026) with ESMTP id l6BO-UHNT1BK; Wed, 2 Jun 2021 10:06:58 -0400 (EDT) Received: from mail03.efficios.com (mail03.efficios.com [167.114.26.124]) by mail.efficios.com (Postfix) with ESMTP id 548823029F3; Wed, 2 Jun 2021 10:06:58 -0400 (EDT) Date: Wed, 2 Jun 2021 10:06:58 -0400 (EDT) From: Mathieu Desnoyers To: Peter Zijlstra Message-ID: <896642516.5866.1622642818225.JavaMail.zimbra@efficios.com> In-Reply-To: <20210602133040.587042016@infradead.org> References: <20210602131225.336600299@infradead.org> <20210602133040.587042016@infradead.org> MIME-Version: 1.0 X-Originating-IP: [167.114.26.124] Thread-Topic: sched: Change task_struct::state Thread-Index: DzXPoSkxk24gPNa4OEu5k5Jl7651YA== X-Mimecast-Impersonation-Protect: Policy=CLT - Impersonation Protection Definition; Similar Internal Domain=false; Similar Monitored External Domain=false; Custom External Domain=false; Mimecast External Domain=false; Newly Observed Domain=false; Internal User Name=false; Custom Display Name List=false; Reply-to Address Mismatch=false; Targeted Threat Dictionary=false; Mimecast Threat Dictionary=false; Custom Threat Dictionary=false X-Scanned-By: MIMEDefang 2.78 on 10.11.54.6 X-loop: dm-devel@redhat.com X-Mailman-Approved-At: Thu, 03 Jun 2021 02:32:49 -0400 Cc: Juri Lelli , Mark Rutland , Pavel Machek , Mike Snitzer , Alexander Shishkin , kgdb-bugreport , Lai Jiangshan , Oleg Nesterov , Ben Segall , linux-mm , dm-devel , Paolo Bonzini , Zefan Li , "H. Peter Anvin" , "Joel Fernandes, Google" , netdev , Jiri Olsa , Alasdair Kergon , Daniel Thompson , Davidlohr Bueso , Vincent Guittot , KVM list , Will Deacon , cgroups , x86 , Ingo Molnar , Mel Gorman , Jakub Kicinski , paulmck , linux-pm , Boqun Feng , Jason Wessel , Josh Triplett , rostedt , linux-block , linux-fsdevel , Borislav Petkov , Alexander Viro , Waiman Long , Namhyung Kim , Thomas Gleixner , acme , Dietmar Eggemann , Jens Axboe , Felipe Balbi , Stephen Boyd , Greg Kroah-Hartman , linux-usb , "Rafael J. Wysocki" , Douglas Anderson , linux-kernel , linux-perf-users , Johannes Weiner , Tejun Heo , John Stultz , Andrew Morton , rcu , bristot , "David S. Miller" Subject: Re: [dm-devel] [PATCH 6/6] sched: Change task_struct::state X-BeenThere: dm-devel@redhat.com X-Mailman-Version: 2.1.12 Precedence: junk List-Id: device-mapper development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: dm-devel-bounces@redhat.com Errors-To: dm-devel-bounces@redhat.com X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=dm-devel-bounces@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit ----- On Jun 2, 2021, at 9:12 AM, Peter Zijlstra peterz@infradead.org wrote: > Change the type and name of task_struct::state. Drop the volatile and > shrink it to an 'unsigned int'. Rename it in order to find all uses > such that we can use READ_ONCE/WRITE_ONCE as appropriate. > [...] > > --- a/block/blk-mq.c > +++ b/block/blk-mq.c [...] > @@ -1559,7 +1560,8 @@ static int fill_psinfo(struct elf_prpsin > psinfo->pr_pgrp = task_pgrp_vnr(p); > psinfo->pr_sid = task_session_vnr(p); > > - i = p->state ? ffz(~p->state) + 1 : 0; > + state = READ_ONCE(p->__state); > + i = state ? ffz(~state) + 1 : 0; > psinfo->pr_state = i; > psinfo->pr_sname = (i > 5) ? '.' : "RSDTZW"[i]; > psinfo->pr_zomb = psinfo->pr_sname == 'Z'; [...] > --- a/include/linux/sched.h > +++ b/include/linux/sched.h > @@ -113,13 +113,13 @@ struct task_group; > __TASK_TRACED | EXIT_DEAD | EXIT_ZOMBIE | \ > TASK_PARKED) > > -#define task_is_running(task) (READ_ONCE((task)->state) == TASK_RUNNING) > +#define task_is_running(task) (READ_ONCE((task)->__state) == TASK_RUNNING) > > -#define task_is_traced(task) ((task->state & __TASK_TRACED) != 0) > +#define task_is_traced(task) ((READ_ONCE(task->__state) & __TASK_TRACED) != 0) > > -#define task_is_stopped(task) ((task->state & __TASK_STOPPED) != 0) > +#define task_is_stopped(task) ((READ_ONCE(task->__state) & __TASK_STOPPED) != > 0) > > -#define task_is_stopped_or_traced(task) ((task->state & (__TASK_STOPPED | > __TASK_TRACED)) != 0) > +#define task_is_stopped_or_traced(task) ((READ_ONCE(task->__state) & > (__TASK_STOPPED | __TASK_TRACED)) != 0) > > #ifdef CONFIG_DEBUG_ATOMIC_SLEEP > > @@ -134,14 +134,14 @@ struct task_group; > do { \ > WARN_ON_ONCE(is_special_task_state(state_value));\ > current->task_state_change = _THIS_IP_; \ > - current->state = (state_value); \ > + WRITE_ONCE(current->__state, (state_value)); \ > } while (0) Why not introduce set_task_state(p) and get_task_state(p) rather than sprinkle READ_ONCE() and WRITE_ONCE() all over the kernel ? Thanks, Mathieu -- Mathieu Desnoyers EfficiOS Inc. http://www.efficios.com -- dm-devel mailing list dm-devel@redhat.com https://listman.redhat.com/mailman/listinfo/dm-devel