From: Andrew Morton <akpm@linux-foundation.org>
To: "Srivatsa S. Bhat" <srivatsa.bhat@linux.vnet.ibm.com>
Cc: peterz@infradead.org, tglx@linutronix.de, mingo@kernel.org,
tj@kernel.org, rusty@rustcorp.com.au, fweisbec@gmail.com,
hch@infradead.org, mgorman@suse.de, riel@redhat.com, bp@suse.de,
rostedt@goodmis.org, mgalbraith@suse.de, ego@linux.vnet.ibm.com,
paulmck@linux.vnet.ibm.com, oleg@redhat.com, rjw@rjwysocki.net,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2/2] CPU hotplug, stop-machine: Plug race-window that leads to "IPI-to-offline-CPU"
Date: Tue, 6 May 2014 13:40:54 -0700 [thread overview]
Message-ID: <20140506134054.8cd531296c8aa5d9c3eff958@linux-foundation.org> (raw)
In-Reply-To: <20140506180258.14375.20181.stgit@srivatsabhat.in.ibm.com>
On Tue, 06 May 2014 23:33:03 +0530 "Srivatsa S. Bhat" <srivatsa.bhat@linux.vnet.ibm.com> wrote:
> --- a/kernel/stop_machine.c
> +++ b/kernel/stop_machine.c
> @@ -165,12 +165,21 @@ static void ack_state(struct multi_stop_data *msdata)
> set_state(msdata, msdata->state + 1);
> }
>
> +/* Holding area for active CPUs, to let all the non-active CPUs go first */
> +static void hold_active_cpus(struct multi_stop_data *msdata,
> + int num_active_cpus)
> +{
> + /* Wait until all the non-active threads ack the state */
> + while (atomic_read(&msdata->thread_ack) > num_active_cpus)
> + cpu_relax();
> +}
The code comments are a bit lame. Can we do a better job of explaining
the overall dynamic behaviour? Help readers to understand the problem
which hold_active_cpus() is solving and how it solves it?
next prev parent reply other threads:[~2014-05-06 20:40 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-05-06 18:02 [PATCH 0/2] CPU hotplug: Fix the long-standing "IPI to offline CPU" issue Srivatsa S. Bhat
2014-05-06 18:02 ` [PATCH 1/2] smp: Print more useful debug info upon receiving IPI on an offline CPU Srivatsa S. Bhat
2014-05-06 20:34 ` Andrew Morton
2014-05-06 21:23 ` Srivatsa S. Bhat
2014-05-06 22:01 ` [PATCH v2 " Srivatsa S. Bhat
2014-05-06 18:03 ` [PATCH 2/2] CPU hotplug, stop-machine: Plug race-window that leads to "IPI-to-offline-CPU" Srivatsa S. Bhat
2014-05-06 20:40 ` Andrew Morton [this message]
2014-05-06 20:42 ` Tejun Heo
2014-05-06 21:27 ` Srivatsa S. Bhat
2014-05-06 22:01 ` [PATCH v2 " Srivatsa S. Bhat
2014-05-10 3:06 ` Tejun Heo
2014-05-11 20:07 ` Srivatsa S. Bhat
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