Re: [PATCH v7 1/3] cgroups: read-write lock CLONE_THREAD forking per threadgroup
On Mon, Jan 24, 2011 at 01:05:29PM -0800, Andrew Morton wrote: > On Sun, 26 Dec 2010 07:09:51 -0500 > Ben Blum <bblum@andrew.cmu.edu> wrote: > > > Adds functionality to read/write lock CLONE_THREAD fork()ing per-threadgroup > > > > From: Ben Blum <bblum@andrew.cmu.edu> > > > > This patch adds an rwsem that lives in a threadgroup's signal_struct that's > > taken for reading in the fork path, under CONFIG_CGROUPS. If another part of > > the kernel later wants to use such a locking mechanism, the CONFIG_CGROUPS > > ifdefs should be changed to a higher-up flag that CGROUPS and the other system > > would both depend on. > > > > This is a pre-patch for cgroup-procs-write.patch. > > > > ... > > > > +/* See the declaration of threadgroup_fork_lock in signal_struct. */ > > +#ifdef CONFIG_CGROUPS > > +static inline void threadgroup_fork_read_lock(struct task_struct *tsk) > > +{ > > + down_read(&tsk->signal->threadgroup_fork_lock); > > +} > > +static inline void threadgroup_fork_read_unlock(struct task_struct *tsk) > > +{ > > + up_read(&tsk->signal->threadgroup_fork_lock); > > +} > > +static inline void threadgroup_fork_write_lock(struct task_struct *tsk) > > +{ > > + down_write(&tsk->signal->threadgroup_fork_lock); > > +} > > +static inline void threadgroup_fork_write_unlock(struct task_struct *tsk) > > +{ > > + up_write(&tsk->signal->threadgroup_fork_lock); > > +} > > +#else > > Risky. sched.h doesn't include rwsem.h. > > We could make it do so, but almost every compilation unit in the kernel > includes sched.h. It would be nicer to make the kernel build > finer-grained, rather than blunter-grained. Don't be afraid to add new > header files if that is one way of doing this! Hmm, good point. But there's also: +#ifdef CONFIG_CGROUPS + struct rw_semaphore threadgroup_fork_lock; +#endif in the signal_struct, also in sched.h, which needs to be there. Or I could change it to a struct pointer with a forward incomplete declaration above, and kmalloc/kfree it? I don't like adding more alloc/free calls but don't know if it's more or less important than header granularity. -- Ben _______________________________________________ Containers mailing list Containers@lists.linux-foundation.org https://lists.linux-foundation.org/mailman/listinfo/containe rs
On Fri, 4 Feb 2011 16:25:15 -0500 Ben Blum <bblum@andrew.cmu.edu> wrote: > On Mon, Jan 24, 2011 at 01:05:29PM -0800, Andrew Morton wrote: > > On Sun, 26 Dec 2010 07:09:51 -0500 > > Ben Blum <bblum@andrew.cmu.edu> wrote: > > > > > Adds functionality to read/write lock CLONE_THREAD fork()ing per-threadgroup > > > > > > From: Ben Blum <bblum@andrew.cmu.edu> > > > > > > This patch adds an rwsem that lives in a threadgroup's signal_struct that's > > > taken for reading in the fork path, under CONFIG_CGROUPS. If another part of > > > the kernel later wants to use such a locking mechanism, the CONFIG_CGROUPS > > > ifdefs should be changed to a higher-up flag that CGROUPS and the other system > > > would both depend on. > > > > > > This is a pre-patch for cgroup-procs-write.patch. > > > > > > ... > > > > > > +/* See the declaration of threadgroup_fork_lock in signal_struct. */ > > > +#ifdef CONFIG_CGROUPS > > > +static inline void threadgroup_fork_read_lock(struct task_struct *tsk) > > > +{ > > > + down_read(&tsk->signal->threadgroup_fork_lock); > > > +} > > > +static inline void threadgroup_fork_read_unlock(struct task_struct *tsk) > > > +{ > > > + up_read(&tsk->signal->threadgroup_fork_lock); > > > +} > > > +static inline void threadgroup_fork_write_lock(struct task_struct *tsk) > > > +{ > > > + down_write(&tsk->signal->threadgroup_fork_lock); > > > +} > > > +static inline void threadgroup_fork_write_unlock(struct task_struct *tsk) > > > +{ > > > + up_write(&tsk->signal->threadgroup_fork_lock); > > > +} > > > +#else > > > > Risky. sched.h doesn't include rwsem.h. > > > > We could make it do so, but almost every compilation unit in the kernel > > includes sched.h. It would be nicer to make the kernel build > > finer-grained, rather than blunter-grained. Don't be afraid to add new > > header files if that is one way of doing this! > > Hmm, good point. But there's also: > > +#ifdef CONFIG_CGROUPS > + struct rw_semaphore threadgroup_fork_lock; > +#endif > > in the signal_struct, also in sched.h, which needs to be there. Or I > could change it to a struct pointer with a forward incomplete > declaration above, and kmalloc/kfree it? I don't like adding more > alloc/free calls but don't know if it's more or less important than > header granularity. What about adding a new header file which includes rwsem.h and sched.h and then defines the new interfaces? _______________________________________________ Containers mailing list Containers@lists.linux-foundation.org https://lists.linux-foundation.org/mailman/listinfo/containe rs
On Fri, Feb 04, 2011 at 01:36:57PM -0800, Andrew Morton wrote: > On Fri, 4 Feb 2011 16:25:15 -0500 > Ben Blum <bblum@andrew.cmu.edu> wrote: > > > On Mon, Jan 24, 2011 at 01:05:29PM -0800, Andrew Morton wrote: > > > On Sun, 26 Dec 2010 07:09:51 -0500 > > > Ben Blum <bblum@andrew.cmu.edu> wrote: > > > > > > > Adds functionality to read/write lock CLONE_THREAD fork()ing per-threadgroup > > > > > > > > From: Ben Blum <bblum@andrew.cmu.edu> > > > > > > > > This patch adds an rwsem that lives in a threadgroup's signal_struct that's > > > > taken for reading in the fork path, under CONFIG_CGROUPS. If another part of > > > > the kernel later wants to use such a locking mechanism, the CONFIG_CGROUPS > > > > ifdefs should be changed to a higher-up flag that CGROUPS and the other system > > > > would both depend on. > > > > > > > > This is a pre-patch for cgroup-procs-write.patch. > > > > > > > > ... > > > > > > > > +/* See the declaration of threadgroup_fork_lock in signal_struct. */ > > > > +#ifdef CONFIG_CGROUPS > > > > +static inline void threadgroup_fork_read_lock(struct task_struct *tsk) > > > > +{ > > > > + down_read(&tsk->signal->threadgroup_fork_lock); > > > > +} > > > > +static inline void threadgroup_fork_read_unlock(struct task_struct *tsk) > > > > +{ > > > > + up_read(&tsk->signal->threadgroup_fork_lock); > > > > +} > > > > +static inline void threadgroup_fork_write_lock(struct task_struct *tsk) > > > > +{ > > > > + down_write(&tsk->signal->threadgroup_fork_lock); > > > > +} > > > > +static inline void threadgroup_fork_write_unlock(struct task_struct *tsk) > > > > +{ > > > > + up_write(&tsk->signal->threadgroup_fork_lock); > > > > +} > > > > +#else > > > > > > Risky. sched.h doesn't include rwsem.h. > > > > > > We could make it do so, but almost every compilation unit in the kernel > > > includes sched.h. It would be nicer to make the kernel build > > > finer-grained, rather than blunter-grained. Don't be afraid to add new > > > header files if that is one way of doing this! > > > > Hmm, good point. But there's also: > > > > +#ifdef CONFIG_CGROUPS > > + struct rw_semaphore threadgroup_fork_lock; > > +#endif > > > > in the signal_struct, also in sched.h, which needs to be there. Or I > > could change it to a struct pointer with a forward incomplete > > declaration above, and kmalloc/kfree it? I don't like adding more > > alloc/free calls but don't know if it's more or less important than > > header granularity. > > What about adding a new header file which includes rwsem.h and sched.h > and then defines the new interfaces? Er, I mean the definition of signal_struct needs rwsem.h as well, not just the threadgroup_fork_* functions. (And I suspect moving signal_struct somewhere else would give bigger problems...) _______________________________________________ Containers mailing list Containers@lists.linux-foundation.org https://lists.linux-foundation.org/mailman/listinfo/containe rs