Commit e0ca1696 authored by Christian Loehle's avatar Christian Loehle Committed by Tejun Heo
Browse files

sched_ext: Introduce scx_bpf_locked_rq() 



Most fields in scx_bpf_cpu_rq() assume that its rq_lock is held.
Furthermore they become meaningless without rq lock, too.
Make a safer version of scx_bpf_cpu_rq() that only returns a rq
if we hold rq lock of that rq.

Also mark the new scx_bpf_locked_rq() as returning NULL as
scx_bpf_cpu_rq() should've been too.

Signed-off-by: default avatarChristian Loehle <christian.loehle@arm.com>
Acked-by: default avatarAndrea Righi <arighi@nvidia.com>
Signed-off-by: default avatarTejun Heo <tj@kernel.org>
parent a5bd6ba3

kernel/sched/ext.c

+23 −0
Original line number Diff line number Diff line
@@ -6357,6 +6357,28 @@ __bpf_kfunc struct rq *scx_bpf_cpu_rq(s32 cpu) 
	return cpu_rq(cpu);

}



/**

 * scx_bpf_locked_rq - Return the rq currently locked by SCX

 *

 * Returns the rq if a rq lock is currently held by SCX.

 * Otherwise emits an error and returns NULL.

 */

__bpf_kfunc struct rq *scx_bpf_locked_rq(void)

{

	struct rq *rq;



	preempt_disable();

	rq = scx_locked_rq();

	if (!rq) {

		preempt_enable();

		scx_kf_error("accessing rq without holding rq lock");

		return NULL;

	}

	preempt_enable();



	return rq;

}



/**

 * scx_bpf_task_cgroup - Return the sched cgroup of a task

 * @p: task of interest
@@ -6521,6 +6543,7 @@ BTF_ID_FLAGS(func, scx_bpf_put_cpumask, KF_RELEASE) 
BTF_ID_FLAGS(func, scx_bpf_task_running, KF_RCU)

BTF_ID_FLAGS(func, scx_bpf_task_cpu, KF_RCU)

BTF_ID_FLAGS(func, scx_bpf_cpu_rq)

BTF_ID_FLAGS(func, scx_bpf_locked_rq, KF_RET_NULL)

#ifdef CONFIG_CGROUP_SCHED

BTF_ID_FLAGS(func, scx_bpf_task_cgroup, KF_RCU | KF_ACQUIRE)

#endif

tools/sched_ext/include/scx/common.bpf.h

+1 −0
Original line number Diff line number Diff line
@@ -103,6 +103,7 @@ s32 scx_bpf_pick_any_cpu(const cpumask_t *cpus_allowed, u64 flags) __ksym; 
bool scx_bpf_task_running(const struct task_struct *p) __ksym;

s32 scx_bpf_task_cpu(const struct task_struct *p) __ksym;

struct rq *scx_bpf_cpu_rq(s32 cpu) __ksym;

struct rq *scx_bpf_locked_rq(void) __ksym;

struct cgroup *scx_bpf_task_cgroup(struct task_struct *p) __ksym __weak;

u64 scx_bpf_now(void) __ksym __weak;

void scx_bpf_events(struct scx_event_stats *events, size_t events__sz) __ksym __weak;