linux-kernel - Re: [PATCH V2 Resend 3/4] workqueue: Schedule work on non-idle cpu instead of current one

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Date:	Fri, 4 Jan 2013 16:41:47 +0530
From:	Viresh Kumar <viresh.kumar@...aro.org>
To:	Tejun Heo <tj@...nel.org>,
	Vincent Guittot <vincent.guittot@...aro.org>
Cc:	pjt@...gle.com, paul.mckenney@...aro.org, tglx@...utronix.de,
	suresh.b.siddha@...el.com, venki@...gle.com, mingo@...hat.com,
	peterz@...radead.org, rostedt@...dmis.org, Arvind.Chauhan@....com,
	linaro-dev@...ts.linaro.org, patches@...aro.org,
	pdsw-power-team@....com, linux-kernel@...r.kernel.org,
	linux-rt-users@...r.kernel.org
Subject: Re: [PATCH V2 Resend 3/4] workqueue: Schedule work on non-idle cpu
 instead of current one

Hi Tejun,

On 27 November 2012 10:49, Viresh Kumar <viresh.kumar@...aro.org> wrote:
> On 26 November 2012 22:45, Tejun Heo <tj@...nel.org> wrote:
>> On Tue, Nov 06, 2012 at 04:08:45PM +0530, Viresh Kumar wrote:
>
>> I'm pretty skeptical about this.  queue_work() w/o explicit CPU
>> assignment has always guaranteed that the work item will be executed
>> on the same CPU.  I don't think there are too many users depending on
>> that but am not sure at all that there are none.  I asked you last
>> time that you would at the very least need to audit most users but it
>> doesn't seem like there has been any effort there.
>
> My bad. I completely missed/forgot that comment from your earlier mails.
> Will do it.

And this is the first thing i did this year :)

So there are almost 1200 files which are using: queue_work, queue_delayed_work,
schedule_work, schedule_delayed_work or schedule_on_each_cpu

Obviously i can't try to understand all of them :) , and so i tried to
search two
strings in them: "cpu" or "processor_id". So, this would catch every
file of these 1200
odd files which use some variables/comment/code with cpu or smp_processor_id or
raw_processor_id, etc..

I got around 650 files with these two searches.. Then i went into
these files to see if
there is anything noticeable, which may break due to this patch...

I got a list of files where cpu/processor_id strings are found, which
may break with
this patch (still can't guarantee as i don't have knowledge of these drivers)...

- arch/powerpc/mm/numa.c
- arch/s390/appldata/appldata_base.c
- arch/s390/kernel/time.c
- arch/s390/kernel/topology.c
- arch/s390/oprofile/hwsampler.c
- arch/x86/kernel/cpu/mcheck/mce.c
- arch/x86/kernel/tsc.c
- arch/x86/kvm/x86.c
- block/blk-core.c
- block/blk-throttle.c
- block/blk-genhd.c
- crypto/cryptd.c
- drivers/base/power/domain.c
- drivers/cpufreq/cpufreq.c
- drivers/hv/vmbus_drv.c
- drivers/infiniband/hw/qib/qib_iba7322.c and
drivers/infiniband/hw/qib/qib_init.c
- drivers/md/dm-crypt.c
- drivers/md/md.c
- drivers/net/ethernet/sfc/efx.c
- drivers/net/ethernet/tile/tilepro.c
- drivers/net/team/team_mode_loadbalance.c
- drivers/oprofile/cpu_buffer.c
- drivers/s390/kvm/kvm_virtio.c
- drivers/scsi/fcoe/fcoe.c
- drivers/tty/sysrq.c
- drivers/xen/pcpu.c
- fs/file.c, file_table.c, fs/fscache/object.c
- include/linux/stop_machine.h, kernel/stop_machine.c
- mm/percpu.c
- mm/slab.c
- mm/vmstat.c
- net/core/flow.c
- net/iucv/iucv.c

I am not sure what to do now :) , can you assist ?
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