LKML Archive on lore.kernel.org
help / color / mirror / Atom feed
From: Jarek Poplawski <jarkao2@gmail.com>
To: Oleg Nesterov <oleg@tv-sign.ru>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	Dipankar Sarma <dipankar@in.ibm.com>,
	Gautham R Shenoy <ego@in.ibm.com>,
	Jarek Poplawski <jarkao2@o2.pl>,
	Srivatsa Vaddagiri <vatsa@in.ibm.com>,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/2] workqueues: shrink cpu_populated_map when CPU dies
Date: Sun, 17 Feb 2008 21:27:39 +0100	[thread overview]
Message-ID: <20080217202739.GA2994@ami.dom.local> (raw)
In-Reply-To: <20080216172259.GA18524@tv-sign.ru>

Hi Oleg,

This patch looks OK to me. But while reading this I got some doubts
in nearby places, so BTW 2 small questions:

1) ... workqueue_cpu_callback(...)
{
	...
        list_for_each_entry(wq, &workqueues, list) {
                cwq = per_cpu_ptr(wq->cpu_wq, cpu);

                switch (action) {
                case CPU_UP_PREPARE:
		...

It looks like not all CPU_ cases are served here: shouldn't
list_for_each_entry() be omitted for them?

2) ... __create_workqueue_key(...)
{
	...
        if (singlethread) {
		...
        } else {
                get_online_cpus();
                spin_lock(&workqueue_lock);
                list_add(&wq->list, &workqueues);

Shouldn't this list_add() be done after all these inits below?

                spin_unlock(&workqueue_lock);

                for_each_possible_cpu(cpu) {
                        cwq = init_cpu_workqueue(wq, cpu);
			...
                }
		...
Thanks,
Jarek P.
 

On Sat, Feb 16, 2008 at 08:22:59PM +0300, Oleg Nesterov wrote:
> When cpu_populated_map was introduced, it was supposed that cwq->thread can
> survive after CPU_DEAD, that is why we never shrink cpu_populated_map.
> 
> This is not very nice, we can safely remove the already dead CPU from the map.
> The only required change is that destroy_workqueue() must hold the hotplug lock
> until it destroys all cwq->thread's, to protect the cpu_populated_map. We could
> make the local copy of cpu mask and drop the lock, but sizeof(cpumask_t) may be
> very large.
> 
> Also, fix the comment near queue_work(). Unless _cpu_down() happens we do
> guarantee the cpu-affinity of the work_struct, and we have users which rely on
> this.
> 
> Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>

  reply	other threads:[~2008-02-17 20:21 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-02-16 17:22 Oleg Nesterov
2008-02-17 20:27 ` Jarek Poplawski [this message]
2008-02-17 23:45   ` Oleg Nesterov
2008-02-18  7:50     ` Jarek Poplawski

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20080217202739.GA2994@ami.dom.local \
    --to=jarkao2@gmail.com \
    --cc=akpm@linux-foundation.org \
    --cc=dipankar@in.ibm.com \
    --cc=ego@in.ibm.com \
    --cc=jarkao2@o2.pl \
    --cc=linux-kernel@vger.kernel.org \
    --cc=oleg@tv-sign.ru \
    --cc=vatsa@in.ibm.com \
    --subject='Re: [PATCH 1/2] workqueues: shrink cpu_populated_map when CPU dies' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).