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author | Tomasz Buchert <tomasz.buchert@inria.fr> | 2010-10-27 15:33:34 -0700 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2010-10-27 18:03:08 -0700 |
commit | 2d3cbf8bc852ac1bc3d098186143c5973f87b753 (patch) | |
tree | 5507f0efa192ac6df884fb0118bfd0e28d758662 /Documentation/cgroups | |
parent | 0bdba580ab052a21e3eda2764ed22d9ee962392b (diff) | |
download | lwn-2d3cbf8bc852ac1bc3d098186143c5973f87b753.tar.gz lwn-2d3cbf8bc852ac1bc3d098186143c5973f87b753.zip |
cgroup_freezer: update_freezer_state() does incorrect state transitions
There are 4 state transitions possible for a freezer. Only FREEZING ->
FROZEN transaction is done lazily. This patch allows update_freezer_state
only to perform this transaction and renames the function to
update_if_frozen.
Moreover is_task_frozen_enough function is removed and its every occurence
is replaced with frozen(). Therefore for a group to become FROZEN every
task must be frozen.
The previous version could trigger a following bug: When cgroup is in the
process of freezing (but none of its tasks are frozen yet),
update_freezer_state() (called from freezer_read or freezer_write) would
incorrectly report that a group is 'THAWED' (because nfrozen = 0),
allowing the transaction FREEZING -> THAWED without writing anything to
'freezer.state'. This is incorrect according to the documentation. This
could result in a 'THAWED' cgroup with frozen tasks inside.
A code to reproduce this bug is available here:
http://pentium.hopto.org/~thinred/repos/linux-misc/freezer_bug2.c
[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: Tomasz Buchert <tomasz.buchert@inria.fr>
Cc: Matt Helsley <matthltc@us.ibm.com>
Cc: Paul Menage <menage@google.com>
Cc: Li Zefan <lizf@cn.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'Documentation/cgroups')
0 files changed, 0 insertions, 0 deletions