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 <jdesfos...@digitalocean.com>
Signed-off-by: Joel Fernandes (Google) <j...@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.hy...@oracle.com>
As the cookie is reference counted, even if inherited, zero this and allow
explicit sharing.
Signed-off-by: Chris Hyser <chris.hy...@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
