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| author | Tejun Heo <tj@kernel.org> | 2015-09-16 18:51:12 +0300 |
|---|---|---|
| committer | Tejun Heo <tj@kernel.org> | 2015-09-16 18:51:12 +0300 |
| commit | 0c986253b939cc14c69d4adbe2b4121bdf4aa220 (patch) | |
| tree | 78c28e9ff07b67baf4c06f72f92bbaa586452c9a /include/linux/sched.h | |
| parent | f9f9e7b776142fb1c0782cade004cc8e0147a199 (diff) | |
| download | linux-0c986253b939cc14c69d4adbe2b4121bdf4aa220.tar.xz | |
Revert "sched, cgroup: replace signal_struct->group_rwsem with a global percpu_rwsem"
This reverts commit d59cfc09c32a2ae31f1c3bc2983a0cd79afb3f14.
d59cfc09c32a ("sched, cgroup: replace signal_struct->group_rwsem with
a global percpu_rwsem") and b5ba75b5fc0e ("cgroup: simplify
threadgroup locking") changed how cgroup synchronizes against task
fork and exits so that it uses global percpu_rwsem instead of
per-process rwsem; unfortunately, the write [un]lock paths of
percpu_rwsem always involve synchronize_rcu_expedited() which turned
out to be too expensive.
Improvements for percpu_rwsem are scheduled to be merged in the coming
v4.4-rc1 merge window which alleviates this issue. For now, revert
the two commits to restore per-process rwsem. They will be re-applied
for the v4.4-rc1 merge window.
Signed-off-by: Tejun Heo <tj@kernel.org>
Link: http://lkml.kernel.org/g/55F8097A.7000206@de.ibm.com
Reported-by: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: stable@vger.kernel.org # v4.2+
Diffstat (limited to 'include/linux/sched.h')
| -rw-r--r-- | include/linux/sched.h | 12 |
1 files changed, 12 insertions, 0 deletions
diff --git a/include/linux/sched.h b/include/linux/sched.h index a4ab9daa387c..b7b9501b41af 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -762,6 +762,18 @@ struct signal_struct { unsigned audit_tty_log_passwd; struct tty_audit_buf *tty_audit_buf; #endif +#ifdef CONFIG_CGROUPS + /* + * group_rwsem prevents new tasks from entering the threadgroup and + * member tasks from exiting,a more specifically, setting of + * PF_EXITING. fork and exit paths are protected with this rwsem + * using threadgroup_change_begin/end(). Users which require + * threadgroup to remain stable should use threadgroup_[un]lock() + * which also takes care of exec path. Currently, cgroup is the + * only user. + */ + struct rw_semaphore group_rwsem; +#endif oom_flags_t oom_flags; short oom_score_adj; /* OOM kill score adjustment */ |