Messages in this thread Patch in this message | | | Subject | Re: [PATCH v8 -tip 17/26] sched: Split the cookie and setup per-task cookie on fork | From | chris hyser <> | Date | Mon, 9 Nov 2020 18:23:13 -0500 |
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> 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 <jdesfossez@digitalocean.com> >> Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org> >> --- >> 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().
-chris
PATCH] sched: zero out the core scheduling cookie on clone
From: chris hyser <chris.hyser@oracle.com>
As the cookie is reference counted, even if inherited, zero this and allow explicit sharing.
Signed-off-by: Chris Hyser <chris.hyser@oracle.com> --- 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
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