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author | Colin Cross <ccross@android.com> | 2011-10-09 02:22:41 +0100 |
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committer | Andy Green <andy.green@linaro.org> | 2011-10-09 02:22:41 +0100 |
commit | 91e792289144d441289ee180a94d3926688e1250 (patch) | |
tree | 8b1cdd8907b762a4af0238719eeca2428342ee7f /drivers/staging | |
parent | 38f28005e61f9a37ce13b644a746f47950931158 (diff) |
cgroup: Remove call to synchronize_rcu in cgroup_attach_task
synchronize_rcu can be very expensive, averaging 100 ms in
some cases. In cgroup_attach_task, it is used to prevent
a task->cgroups pointer dereferenced in an RCU read side
critical section from being invalidated, by delaying the
call to put_css_set until after an RCU grace period.
To avoid the call to synchronize_rcu, make the put_css_set
call rcu-safe by moving the deletion of the css_set links
into free_css_set_work, scheduled by the rcu callback
free_css_set_rcu.
The decrement of the cgroup refcount is no longer
synchronous with the call to put_css_set, which can result
in the cgroup refcount staying positive after the last call
to cgroup_attach_task returns. To allow the cgroup to be
deleted with cgroup_rmdir synchronously after
cgroup_attach_task, have rmdir check the refcount of all
associated css_sets. If cgroup_rmdir is called on a cgroup
for which the css_sets all have refcount zero but the
cgroup refcount is nonzero, reuse the rmdir waitqueue to
block the rmdir until free_css_set_work is called.
Signed-off-by: Colin Cross <ccross@android.com>
Diffstat (limited to 'drivers/staging')
0 files changed, 0 insertions, 0 deletions