| From: |
| Gautham R Shenoy <ego@in.ibm.com> |
| To: |
| Linus Torvalds <torvalds@linux-foundation.org>,
Andrew Morton <akpm@linux-foundation.org> |
| Subject: |
| [RFC PATCH 0/5] Refcount based Cpu Hotplug. V2 |
| Date: |
| Wed, 24 Oct 2007 10:59:31 +0530 |
| Message-ID: |
| <20071024052931.GA22722@in.ibm.com> |
| Cc: |
| linux-kernel@vger.kernel.org, Rusty Russel <rusty@rustcorp.com.au>,
Srivatsa Vaddagiri <vatsa@in.ibm.com>,
Dipankar Sarma <dipankar@in.ibm.com>,
Ingo Molnar <mingo@elte.hu>, Oleg Nesterov <oleg@tv-sign.ru>,
Paul E McKenney <paulmck@us.ibm.com>,
Richard Gooch <rgooch@atnf.csiro.au>,
Tigran Aivazian <tigran@aivazian.fs.co.uk>,
Shoahua Li <shaohua.li@linux.com>,
Ralf Baechle <ralf@linux-mips.org>,
Heiko Carstens <heiko.carstens@de.ibm.com>,
Nathan Lynch <ntl@pobox.com>,
David Miller <davem@davemloft.net>, Paul Jackson <pj@sgi.com>,
Josh Triplett <josh@freedesktop.org>,
Christoph Lameter <clameter@sgi.com>,
Pekka Enberg <penberg@cs.helsinki.fi>,
Akinobu Mita <akinobu.mita@gmail.com> |
| Archive‑link: | |
Article |
Hello everyone,
This is the version 2 of the refcount based cpu-hotplug "locking"
implementation.
It incorporates the review comments from the first posting which
can be found here --> http://lkml.org/lkml/2007/10/16/118.
Changes since v1:
- !CONFIG_HOTPLUG_CPU part is now handled correctly, thanks
to the patch from Paul Jackson.
- The cpu_hotplug_begin() uses a waitqueue instead of a completion struct
where a writer can wait while there are active readers in the system.
- Provided a new API's cpu_maps_update_begin(), cpu_maps_update_done()
for serializing the updates to cpu_present_map and cpu_online_map.
Thus threads which update the cpu_present_map should now call
cpu_maps_update_begin instead of lock_cpu_hotplug(), since they play the
role of writers.
- pseries_processor_add() , pseries_processor_remove() now use
cpu_maps_update_begin()/cpu_maps_update_done() in place of
lock_cpu_hotplug()/unlock_cpu_hotplug().
- Replaced the workqueue_mutex with workqueue_lock, which is a spinlock
and guards the workqueues list.
- Updated Documentation/cpu-hotplug.txt to reflect get_online_cpus(),
put_online_cpus() in place of the old lock_cpu_hotplug(),
unlock_cpu_hotplug().
I'm Cc'ing the different subsystem maintainers who might be affected
by the changes in the patchstack. Especially if they rely on
lock_cpu_hotplug() to provide them protection for their local data
structures as well.
The patchstack which is based against 2.6.23-mm1 has behaved well
when it was stress tested with kernbench running while continuously
performing cpu-hotplug operations on i386, x86_64 and ppc64.
Awaiting your feedback.
Thanks and Regards
gautham.
--
Gautham R Shenoy
Linux Technology Center
IBM India.
"Freedom comes with a price tag of responsibility, which is still a bargain,
because Freedom is priceless!"
