diff options
| author | Tejun Heo <tj@kernel.org> | 2015-05-13 16:35:17 -0400 |
|---|---|---|
| committer | Tejun Heo <tj@kernel.org> | 2015-05-26 20:35:00 -0400 |
| commit | d59cfc09c32a2ae31f1c3bc2983a0cd79afb3f14 (patch) | |
| tree | 077533cef8f5e16c8f7fd65d7e255d75828f3820 /include/linux/cgroup-defs.h | |
| parent | 7d7efec368d537226142cbe559f45797f18672f9 (diff) | |
sched, cgroup: replace signal_struct->group_rwsem with a global percpu_rwsem
The cgroup side of threadgroup locking uses signal_struct->group_rwsem
to synchronize against threadgroup changes. This per-process rwsem
adds small overhead to thread creation, exit and exec paths, forces
cgroup code paths to do lock-verify-unlock-retry dance in a couple
places and makes it impossible to atomically perform operations across
multiple processes.
This patch replaces signal_struct->group_rwsem with a global
percpu_rwsem cgroup_threadgroup_rwsem which is cheaper on the reader
side and contained in cgroups proper. This patch converts one-to-one.
This does make writer side heavier and lower the granularity; however,
cgroup process migration is a fairly cold path, we do want to optimize
thread operations over it and cgroup migration operations don't take
enough time for the lower granularity to matter.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Diffstat (limited to 'include/linux/cgroup-defs.h')
| -rw-r--r-- | include/linux/cgroup-defs.h | 27 |
1 files changed, 25 insertions, 2 deletions
diff --git a/include/linux/cgroup-defs.h b/include/linux/cgroup-defs.h index 1b8c93806dbd..7d83d7f73420 100644 --- a/include/linux/cgroup-defs.h +++ b/include/linux/cgroup-defs.h @@ -461,8 +461,31 @@ struct cgroup_subsys { unsigned int depends_on; }; -void cgroup_threadgroup_change_begin(struct task_struct *tsk); -void cgroup_threadgroup_change_end(struct task_struct *tsk); +extern struct percpu_rw_semaphore cgroup_threadgroup_rwsem; + +/** + * cgroup_threadgroup_change_begin - threadgroup exclusion for cgroups + * @tsk: target task + * + * Called from threadgroup_change_begin() and allows cgroup operations to + * synchronize against threadgroup changes using a percpu_rw_semaphore. + */ +static inline void cgroup_threadgroup_change_begin(struct task_struct *tsk) +{ + percpu_down_read(&cgroup_threadgroup_rwsem); +} + +/** + * cgroup_threadgroup_change_end - threadgroup exclusion for cgroups + * @tsk: target task + * + * Called from threadgroup_change_end(). Counterpart of + * cgroup_threadcgroup_change_begin(). + */ +static inline void cgroup_threadgroup_change_end(struct task_struct *tsk) +{ + percpu_up_read(&cgroup_threadgroup_rwsem); +} #else /* CONFIG_CGROUPS */ |