netdev - [PATCH bpf-next 1/2] sched: introduce this_rq_is

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Date:   Wed, 9 Oct 2019 23:19:15 -0700
From:   Song Liu <songliubraving@...com>
To:     <linux-kernel@...r.kernel.org>, <bpf@...r.kernel.org>,
        <netdev@...r.kernel.org>
CC:     <kernel-team@...com>, Song Liu <songliubraving@...com>,
        <stable@...r.kernel.org>, Peter Zijlstra <peterz@...radead.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Tejun Heo <tj@...nel.org>
Subject: [PATCH bpf-next 1/2] sched: introduce this_rq_is_locked()

this_rq_is_locked() is introduced to check whether current CPU is holding
rq_lock(). This will be used in bpf/stackmap.c to decide whether is safe
to call up_read(), which may call rq_lock() for the same CPU.

Fixes: commit 615755a77b24 ("bpf: extend stackmap to save binary_build_id+offset instead of address")
Cc: stable@...r.kernel.org # v4.17+
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Alexei Starovoitov <ast@...nel.org>
Cc: Daniel Borkmann <daniel@...earbox.net>
Cc: Tejun Heo <tj@...nel.org>
Signed-off-by: Song Liu <songliubraving@...com>
---
 include/linux/sched.h | 1 +
 kernel/sched/core.c   | 8 ++++++++
 2 files changed, 9 insertions(+)

diff --git a/include/linux/sched.h b/include/linux/sched.h
index 2c2e56bd8913..fb0fcbd1b6f6 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1995,4 +1995,5 @@ int sched_trace_rq_cpu(struct rq *rq);

 const struct cpumask *sched_trace_rd_span(struct root_domain *rd);

+bool this_rq_is_locked(void);
 #endif
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 7880f4f64d0e..577cbe7c05fc 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -138,6 +138,14 @@ struct rq *task_rq_lock(struct task_struct *p, struct rq_flags *rf)
 	}
 }

+bool this_rq_is_locked(void)
+{
+	struct rq *rq;
+
+	rq = this_rq();
+	return raw_spin_is_locked(&rq->lock);
+}
+
 /*
  * RQ-clock updating methods:
  */
--
2.17.1