On 06/25, Peter Zijlstra wrote:
>
> On Tue, Jun 23, 2015 at 07:24:16PM +0200, Oleg Nesterov wrote:
> >
> > lock_stop_cpus_works(cpumask)
> > {
> > for_each_cpu(cpu, cpumask)
> > mutex_lock(per_cpu(cpu_stopper_task, cpu).work_mutex);
> > }
> >
> > unlock_stop_cpus_works(cpumask)
> > {
> > for_each_cpu(cpu, cpumask)
> > mutex_lock(...);
> > }
> >
> > which should be used instead of stop_cpus_mutex. After this change
> > stop_two_cpus() can just use stop_cpus().
>
> Right, lockdep annotating that will be 'interesting' though.
Sure, and this is too inefficient, this is only to explain what
I mean.
How about this series? Untested. For review.
> And
> stop_two_cpus() then has the problem of allocating a cpumask.
Yes, but we can avoid this, see the changelog in 5/6.
> Simpler to
> let it keep 'abuse' the queueing spinlock in there.
Not sure.
And note that this series kills stop_cpus_mutex, so that multiple
stop_cpus()'s / stop_machine()'s can run in parallel if cpumask's
do not overlap.
Note also the changelog in 6/6, we can simplify + optimize this code
a bit more.
What do you think?
Oleg.
include/linux/lglock.h | 5 -
kernel/locking/lglock.c | 22 -----
kernel/stop_machine.c | 197 ++++++++++++++++++++++++++++-------------------
3 files changed, 119 insertions(+), 105 deletions(-)
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