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From: "Rafael J. Wysocki" <rjw@rjwysocki.net>
To: Tejun Heo <tj@kernel.org>
Cc: Nigel Cunningham <nigel@nigelcunningham.com.au>,
        "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>,
        Jens Axboe <axboe@kernel.dk>, tomaz.solc@tablix.org,
        aaron.lu@intel.com, linux-kernel@vger.kernel.org,
        Oleg Nesterov <oleg@redhat.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Fengguang Wu <fengguang.wu@intel.com>
Subject: Re: [PATCH] libata, freezer: avoid block device removal while system is frozen
Date: Wed, 18 Dec 2013 23:04:40 +0100
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On Wednesday, December 18, 2013 04:41:28 PM Tejun Heo wrote:
> On Wed, Dec 18, 2013 at 04:39:36PM -0500, Tejun Heo wrote:
> > Yeah, we can just rip out the whole freezer support and let the
> > caller's pm notification hooks implement it by doing
> > 
> > 	workqueue_set_max_active(wq, 0);
> > 	flush_workqueue(wq);
> 
> Oops, the above doesn't work but I can trivially add a new interface
> for this.  Something which waits for the max_active to drop below the
> newly set level before returning.
> 
> 	workqueue_set_max_active_and_wait(wq, 0);

If you add that, I can convert the PM workqueue to using it and then
we can go through all of the existing users and make similar changes - or
just make them non-freezable if there's no good reason for freezing those
particular ones.

Thanks,
Rafael