Messages in this thread | | | Date | Wed, 28 Jul 2010 18:28:13 +0900 | From | KAMEZAWA Hiroyuki <> | Subject | Re: [RFC] [PATCH v3 1/2] cgroups: read-write lock CLONE_THREAD forking per threadgroup |
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On Wed, 28 Jul 2010 04:29:53 -0400 Ben Blum <bblum@andrew.cmu.edu> wrote:
> On Mon, Jun 28, 2010 at 11:43:59AM -0400, Ben Blum wrote: > > On Mon, Jun 28, 2010 at 04:10:31PM +0900, KAMEZAWA Hiroyuki wrote: > > > By the way, IMHO, hiding lock in cgroup_fork() and cgroup_post_fork() doesn't > > > seem good idea. How about a code like this ? > > > > > > read_lock_thread_clone(current); > > > cgroup_fork(); > > > ..... > > > cgroup_post_fork(); > > > read_unlock_thrad_clone(current); > > > > > > We may have chances to move these lock to better position if cgroup is > > > an only user. > > > > I didn't do that out of a desire to change fork.c as little as possible, > > but that does look better than what I've got. Those two functions should > > be in fork.c under #ifdef CONFIG_CGROUPS. > > I'm looking at this now and am not sure where the best place to put > these is: > > 1) Don't make new functions, just put: > > #ifdef CONFIG_CGROUPS > if (clone_flags & CLONE_THREAD) > down/up_read(...); > #endif > > directly in copy_process() in fork.c. Simplest, but uglifies the code. > > 2) Make static helper functions in fork.c. Good, but not consistent with > directly using the lock in write-side (attach_proc). > > 3) Define inline functions under #ifdef CONFIG_CGROUPS in sched.h, just > under the declaration of the lock. Most robust, but I'm hesitant to add > unneeded stuff to such a popular header file. > > Any opinions? >
My point was simple. Because copy_process() is very important path, the new lock should be visible in copy_process() or kernek/fork.c. "If the lock is visible in copy_process(), the reader can notice it".
Then, I offer you 2 options.
rename cgroup_fork() and cgroup_post_fork() as cgroup_fork_lock() and cgroup_post_fork_unlock()
Now, the lock is visible and the change is minimum.
Or add the definition of lock/unlock to cgroup.h and include it from kernel/fork.c
Thanks, -Kame
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