Hi Chris, On Mon, Nov 09, 2020 at 06:23:13PM -0500, chris hyser wrote: > > On 10/19/20 9:43 PM, Joel Fernandes (Google) wrote: > > > In order to prevent interference and clearly support both per-task and > > > CGroup > > > APIs, split the cookie into 2 and allow it to be set from either > > > per-task, or > > > CGroup API. The final cookie is the combined value of both and is > > > computed when > > > the stop-machine executes during a change of cookie. > > > > > > Also, for the per-task cookie, it will get weird if we use pointers of any > > > emphemeral objects. For this reason, introduce a refcounted object who's > > > sole > > > purpose is to assign unique cookie value by way of the object's pointer. > > > > > > While at it, refactor the CGroup code a bit. Future patches will > > > introduce more > > > APIs and support. > > > > > > Tested-by: Julien Desfossez <[email protected]> > > > Signed-off-by: Joel Fernandes (Google) <[email protected]> > > > --- > > > include/linux/sched.h | 2 + > > > kernel/sched/core.c | 241 ++++++++++++++++++++++++++++++++++++++++-- > > > kernel/sched/debug.c | 4 + > > > 3 files changed, 236 insertions(+), 11 deletions(-) > > > > > > diff --git a/include/linux/sched.h b/include/linux/sched.h > > > index fe6f225bfbf9..c6034c00846a 100644 > > > --- a/include/linux/sched.h > > > +++ b/include/linux/sched.h > > > @@ -688,6 +688,8 @@ struct task_struct { > > > #ifdef CONFIG_SCHED_CORE > > > struct rb_node core_node; > > > unsigned long core_cookie; > > > + unsigned long core_task_cookie; > > > + unsigned long core_group_cookie; > > > unsigned int core_occupation; > > > #endif > > > diff --git a/kernel/sched/core.c b/kernel/sched/core.c > > > index bab4ea2f5cd8..30a9e4cb5ce1 100644 > > > --- a/kernel/sched/core.c > > > +++ b/kernel/sched/core.c > > > @@ -346,11 +346,14 @@ void sched_core_put(void) > > > mutex_unlock(&sched_core_mutex); > > > } > > > +static int sched_core_share_tasks(struct task_struct *t1, struct > > > task_struct *t2); > > > + > > > #else /* !CONFIG_SCHED_CORE */ > > > static inline void sched_core_enqueue(struct rq *rq, struct > > > task_struct *p) { } > > > static inline void sched_core_dequeue(struct rq *rq, struct task_struct > > > *p) { } > > > static bool sched_core_enqueued(struct task_struct *task) { return > > > false; } > > > +static int sched_core_share_tasks(struct task_struct *t1, struct > > > task_struct *t2) { } > > > #endif /* CONFIG_SCHED_CORE */ > > > @@ -3583,6 +3586,20 @@ int sched_fork(unsigned long clone_flags, struct > > > task_struct *p) > > > #endif > > > #ifdef CONFIG_SCHED_CORE > > > RB_CLEAR_NODE(&p->core_node); > > > + > > > + /* > > > + * Tag child via per-task cookie only if parent is tagged via > > > per-task > > > + * cookie. This is independent of, but can be additive to the CGroup > > > tagging. > > > + */ > > > + if (current->core_task_cookie) { > > > + > > > + /* If it is not CLONE_THREAD fork, assign a unique per-task tag. > > > */ > > > + if (!(clone_flags & CLONE_THREAD)) { > > > + return sched_core_share_tasks(p, p); > > > + } > > > + /* Otherwise share the parent's per-task tag. */ > > > + return sched_core_share_tasks(p, current); > > > + } > > > #endif > > > return 0; > > > } > > sched_core_share_tasks() looks at the value of the new tasks core_task_cookie > which is non-zero on a > process or thread clone and causes underflow for both the enable flag itself > and for cookie ref counts. > > So just zero it in __sched_fork().
Since I am going to split this into a new patch, could you please send me a detailed commit message explaining the issue? I feel the below one liner is unclear / insufficient as a commit message. thanks, - Joel > -chris > > > PATCH] sched: zero out the core scheduling cookie on clone > > From: chris hyser <[email protected]> > > As the cookie is reference counted, even if inherited, zero this and allow > explicit sharing. > > Signed-off-by: Chris Hyser <[email protected]> > --- > kernel/sched/core.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/kernel/sched/core.c b/kernel/sched/core.c > index fd3cc03..2af0ea6 100644 > --- a/kernel/sched/core.c > +++ b/kernel/sched/core.c > @@ -3378,6 +3378,9 @@ static void __sched_fork(unsigned long clone_flags, > struct task_struct *p) > p->capture_control = NULL; > #endif > init_numa_balancing(clone_flags, p); > +#ifdef CONFIG_SCHED_CORE > + p->core_task_cookie = 0; > +#endif > #ifdef CONFIG_SMP > p->wake_entry.u_flags = CSD_TYPE_TTWU; > #endif > -- > 1.8.3.1 >
