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author | Paul Menage <menage@google.com> | 2009-01-07 18:08:38 -0800 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2009-01-08 08:31:10 -0800 |
commit | e7c5ec9193d32b9559a3bb8893ceedbda85201ff (patch) | |
tree | fd7505c03e2c7525a110a702907c0604c233e2d9 /kernel/cgroup_debug.c | |
parent | 2cb378c862777d050c20db903b119a029845fdcb (diff) | |
download | kernel_samsung_aries-e7c5ec9193d32b9559a3bb8893ceedbda85201ff.zip kernel_samsung_aries-e7c5ec9193d32b9559a3bb8893ceedbda85201ff.tar.gz kernel_samsung_aries-e7c5ec9193d32b9559a3bb8893ceedbda85201ff.tar.bz2 |
cgroups: add css_tryget()
Add css_tryget(), that obtains a counted reference on a CSS. It is used
in situations where the caller has a "weak" reference to the CSS, i.e.
one that does not protect the cgroup from removal via a reference count,
but would instead be cleaned up by a destroy() callback.
css_tryget() will return true on success, or false if the cgroup is being
removed.
This is similar to Kamezawa Hiroyuki's patch from a week or two ago, but
with the difference that in the event of css_tryget() racing with a
cgroup_rmdir(), css_tryget() will only return false if the cgroup really
does get removed.
This implementation is done by biasing css->refcnt, so that a refcnt of 1
means "releasable" and 0 means "released or releasing". In the event of a
race, css_tryget() distinguishes between "released" and "releasing" by
checking for the CSS_REMOVED flag in css->flags.
Signed-off-by: Paul Menage <menage@google.com>
Tested-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Li Zefan <lizf@cn.fujitsu.com>
Cc: Balbir Singh <balbir@in.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'kernel/cgroup_debug.c')
0 files changed, 0 insertions, 0 deletions