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Re: [PATCH] cgroup: Remove RCU from task->cgroups [message #41916 is a reply to message #41911]

Sun, 21 November 2010 23:02

Colin Cross
Messages: 15
Registered: November 2010

Junior Member

On Sat, Nov 20, 2010 at 6:00 PM, Colin Cross <ccross@android.com> wrote:
> The synchronize_rcu call in cgroup_attach_task can be very
> expensive. All fastpath accesses to task->cgroups already
> use task_lock() or cgroup_lock() to protect against updates,
> and only the CGROUP_DEBUG files have RCU read-side critical
> sections.
>
> This patch replaces rcu_read_lock() with task_lock(current)
> around the debug file acceses to current->cgroups and removes
> the synchronize_rcu call in cgroup_attach_task.
>
> Signed-off-by: Colin Cross <ccross@android.com>
> ---
> kernel/cgroup.c | 22 ++++++++--------------
> 1 files changed, 8 insertions(+), 14 deletions(-)
>

This patch isn't correct, there's an rcu_dereference I missed inside
task_group(), and that's the important one.
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[Message index]

		[PATCH] cgroup: Remove RCU from task->cgroups By: Colin Cross on Sun, 21 November 2010 02:00
		Re: [PATCH] cgroup: Remove RCU from task->cgroups By: Colin Cross on Sun, 21 November 2010 23:02
		[PATCH] cgroup: Convert synchronize_rcu to call_rcu in cgroup_attach_task By: Colin Cross on Mon, 22 November 2010 04:06
		Re: [PATCH] cgroup: Convert synchronize_rcu to call_rcu in cgroup_attach_task By: Colin Cross on Tue, 23 November 2010 08:58
		Re: [PATCH] cgroup: Convert synchronize_rcu to call_rcu in cgroup_attach_task By: Colin Cross on Tue, 23 November 2010 20:22
		Re: [PATCH] cgroup: Convert synchronize_rcu to call_rcu in cgroup_attach_task By: Colin Cross on Wed, 24 November 2010 02:10
		[PATCH 2/2] cgroup: Remove call to synchronize_rcu in cgroup_attach_task By: Colin Cross on Wed, 24 November 2010 05:37
		Re: [PATCH 2/2] cgroup: Remove call to synchronize_rcu in cgroup_attach_task By: Bryan Huntsman on Fri, 28 January 2011 01:17
		[PATCH 1/2] cgroup: Set CGRP_RELEASABLE when adding to a cgroup By: Colin Cross on Wed, 24 November 2010 05:37
		Re: [PATCH 1/2] cgroup: Set CGRP_RELEASABLE when adding to a cgroup By: Colin Cross on Thu, 25 November 2010 00:11
		Re: [PATCH 1/2] cgroup: Set CGRP_RELEASABLE when adding to a cgroup By: Colin Cross on Thu, 25 November 2010 00:18
		Re: [PATCH 1/2] cgroup: Set CGRP_RELEASABLE when adding to a cgroup By: Colin Cross on Fri, 03 December 2010 03:07
		Re: [PATCH 1/2] cgroup: Set CGRP_RELEASABLE when adding to a cgroup By: Colin Cross on Fri, 17 December 2010 01:12
		Re: [PATCH 1/2] cgroup: Set CGRP_RELEASABLE when adding to a cgroup By: Bryan Huntsman on Fri, 28 January 2011 01:17
		Re: [PATCH 1/2] cgroup: Set CGRP_RELEASABLE when adding to a cgroup By: Michael Bohan on Fri, 28 January 2011 01:48

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