[PATCH bpf-next 1/2] sched: introduce this_rq_is_locked()

From: Song Liu <songliubraving@fb.com>
To: <linux-kernel@vger.kernel.org>, <bpf@vger.kernel.org>,
	<netdev@vger.kernel.org>
Cc: <kernel-team@fb.com>, Song Liu <songliubraving@fb.com>,
	<stable@vger.kernel.org>, Peter Zijlstra <peterz@infradead.org>,
	Alexei Starovoitov <ast@kernel.org>,
	Daniel Borkmann <daniel@iogearbox.net>, Tejun Heo <tj@kernel.org>
Subject: [PATCH bpf-next 1/2] sched: introduce this_rq_is_locked()
Date: Wed, 9 Oct 2019 23:19:15 -0700	[thread overview]
Message-ID: <20191010061916.198761-2-songliubraving@fb.com> (raw)
In-Reply-To: <20191010061916.198761-1-songliubraving@fb.com>

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@vger.kernel.org # v4.17+
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: Tejun Heo <tj@kernel.org>
Signed-off-by: Song Liu <songliubraving@fb.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
