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author | Paul Turner <pjt@google.com> | 2013-10-16 11:16:27 -0700 |
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committer | Ingo Molnar <mingo@kernel.org> | 2013-10-29 12:02:23 +0100 |
commit | 0ac9b1c21874d2490331233b3242085f8151e166 (patch) | |
tree | 76199cdef57f1bacd3b0d81aba280e062d81bd73 /arch/mips | |
parent | 927b54fccbf04207ec92f669dce6806848cbec7d (diff) | |
download | op-kernel-dev-0ac9b1c21874d2490331233b3242085f8151e166.zip op-kernel-dev-0ac9b1c21874d2490331233b3242085f8151e166.tar.gz |
sched: Guarantee new group-entities always have weight
Currently, group entity load-weights are initialized to zero. This
admits some races with respect to the first time they are re-weighted in
earlty use. ( Let g[x] denote the se for "g" on cpu "x". )
Suppose that we have root->a and that a enters a throttled state,
immediately followed by a[0]->t1 (the only task running on cpu[0])
blocking:
put_prev_task(group_cfs_rq(a[0]), t1)
put_prev_entity(..., t1)
check_cfs_rq_runtime(group_cfs_rq(a[0]))
throttle_cfs_rq(group_cfs_rq(a[0]))
Then, before unthrottling occurs, let a[0]->b[0]->t2 wake for the first
time:
enqueue_task_fair(rq[0], t2)
enqueue_entity(group_cfs_rq(b[0]), t2)
enqueue_entity_load_avg(group_cfs_rq(b[0]), t2)
account_entity_enqueue(group_cfs_ra(b[0]), t2)
update_cfs_shares(group_cfs_rq(b[0]))
< skipped because b is part of a throttled hierarchy >
enqueue_entity(group_cfs_rq(a[0]), b[0])
...
We now have b[0] enqueued, yet group_cfs_rq(a[0])->load.weight == 0
which violates invariants in several code-paths. Eliminate the
possibility of this by initializing group entity weight.
Signed-off-by: Paul Turner <pjt@google.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20131016181627.22647.47543.stgit@sword-of-the-dawn.mtv.corp.google.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'arch/mips')
0 files changed, 0 insertions, 0 deletions