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[80.7.220.175]) by smtp.gmail.com with ESMTPSA id p16sm16000678wrs.52.2021.06.07.03.45.01 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 07 Jun 2021 03:45:03 -0700 (PDT) Date: Mon, 7 Jun 2021 11:45:00 +0100 From: Daniel Thompson To: Peter Zijlstra Cc: Thomas Gleixner , Ingo Molnar , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Daniel Bristot de Oliveira , Borislav Petkov , x86@kernel.org, "H. Peter Anvin" , Jens Axboe , Alasdair Kergon , Mike Snitzer , dm-devel@redhat.com, "David S. Miller" , Jakub Kicinski , Felipe Balbi , Greg Kroah-Hartman , Alexander Viro , Tejun Heo , Zefan Li , Johannes Weiner , Jason Wessel , Douglas Anderson , Arnaldo Carvalho de Melo , Mark Rutland , Alexander Shishkin , Jiri Olsa , Namhyung Kim , "Rafael J. Wysocki" , Pavel Machek , Will Deacon , Waiman Long , Boqun Feng , Oleg Nesterov , Davidlohr Bueso , "Paul E. McKenney" , Josh Triplett , Mathieu Desnoyers , Lai Jiangshan , Joel Fernandes , John Stultz , Stephen Boyd , Andrew Morton , Paolo Bonzini , linux-kernel@vger.kernel.org, linux-block@vger.kernel.org, netdev@vger.kernel.org, linux-usb@vger.kernel.org, linux-fsdevel@vger.kernel.org, cgroups@vger.kernel.org, kgdb-bugreport@lists.sourceforge.net, linux-perf-users@vger.kernel.org, linux-pm@vger.kernel.org, rcu@vger.kernel.org, linux-mm@kvack.org, kvm@vger.kernel.org Subject: Re: [PATCH 6/6] sched: Change task_struct::state Message-ID: <20210607104500.sopvslejuoxwzhrs@maple.lan> References: <20210602131225.336600299@infradead.org> <20210602133040.587042016@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210602133040.587042016@infradead.org> X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: 7EFE2541 Authentication-Results: imf29.hostedemail.com; dkim=pass header.d=linaro.org header.s=google header.b=fokBrG+2; dmarc=pass (policy=none) header.from=linaro.org; spf=pass (imf29.hostedemail.com: domain of daniel.thompson@linaro.org designates 209.85.221.42 as permitted sender) smtp.mailfrom=daniel.thompson@linaro.org X-Stat-Signature: mpoo3d1g7urjrshxp8i3i1hobgn5f98z X-HE-Tag: 1623062701-709468 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Wed, Jun 02, 2021 at 03:12:31PM +0200, Peter Zijlstra 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. > > Signed-off-by: Peter Zijlstra (Intel) > --- > ... > kernel/debug/kdb/kdb_support.c | 18 +++++++------ > ... > --- a/kernel/debug/kdb/kdb_support.c > +++ b/kernel/debug/kdb/kdb_support.c > @@ -609,23 +609,25 @@ unsigned long kdb_task_state_string(cons > */ > char kdb_task_state_char (const struct task_struct *p) > { > - int cpu; > - char state; > + unsigned int p_state; > unsigned long tmp; > + char state; > + int cpu; > > if (!p || > copy_from_kernel_nofault(&tmp, (char *)p, sizeof(unsigned long))) > return 'E'; > > cpu = kdb_process_cpu(p); > - state = (p->state == 0) ? 'R' : > - (p->state < 0) ? 'U' : > - (p->state & TASK_UNINTERRUPTIBLE) ? 'D' : > - (p->state & TASK_STOPPED) ? 'T' : > - (p->state & TASK_TRACED) ? 'C' : > + p_state = READ_ONCE(p->__state); > + state = (p_state == 0) ? 'R' : > + (p_state < 0) ? 'U' : Looks like the U here stands for Unreachable since this patch makes it more obvious that this clause is (and previously was) exactly that! Dropping the U state would be good since I guess this will show up as a "new" warning in some tools. However it was a preexisting problem so with or without this cleaned up: Acked-by: Daniel Thompson Daniel. > + (p_state & TASK_UNINTERRUPTIBLE) ? 'D' : > + (p_state & TASK_STOPPED) ? 'T' : > + (p_state & TASK_TRACED) ? 'C' : > (p->exit_state & EXIT_ZOMBIE) ? 'Z' : > (p->exit_state & EXIT_DEAD) ? 'E' : > - (p->state & TASK_INTERRUPTIBLE) ? 'S' : '?'; > + (p_state & TASK_INTERRUPTIBLE) ? 'S' : '?'; > if (is_idle_task(p)) { > /* Idle task. Is it really idle, apart from the kdb > * interrupt? */