Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Date:   Mon,  4 Jul 2022 17:05:10 +0200
In-Reply-To: <20220704150514.48816-1-elver@google.com>
Message-Id: <20220704150514.48816-11-elver@google.com>
Mime-Version: 1.0
References: <20220704150514.48816-1-elver@google.com>
Subject: [PATCH v3 10/14] locking/percpu-rwsem: Add percpu_is_write_locked()
 and percpu_is_read_locked()
From:   Marco Elver <elver@google.com>
To:     elver@google.com, Peter Zijlstra <peterz@infradead.org>,
        Frederic Weisbecker <frederic@kernel.org>,
        Ingo Molnar <mingo@kernel.org>
Cc:     Thomas Gleixner <tglx@linutronix.de>,
        Arnaldo Carvalho de Melo <acme@kernel.org>,
        Mark Rutland <mark.rutland@arm.com>,
        Alexander Shishkin <alexander.shishkin@linux.intel.com>,
        Jiri Olsa <jolsa@redhat.com>,
        Namhyung Kim <namhyung@kernel.org>,
        Dmitry Vyukov <dvyukov@google.com>,
        Michael Ellerman <mpe@ellerman.id.au>,
        linuxppc-dev@lists.ozlabs.org, linux-perf-users@vger.kernel.org,
        x86@kernel.org, linux-sh@vger.kernel.org,
        kasan-dev@googlegroups.com, linux-kernel@vger.kernel.org
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

Implement simple accessors to probe percpu-rwsem's locked state:
percpu_is_write_locked(), percpu_is_read_locked().

Signed-off-by: Marco Elver <elver@google.com>
Reviewed-by: Dmitry Vyukov <dvyukov@google.com>
---
v2:
* New patch.
---
 include/linux/percpu-rwsem.h  | 6 ++++++
 kernel/locking/percpu-rwsem.c | 6 ++++++
 2 files changed, 12 insertions(+)

diff --git a/include/linux/percpu-rwsem.h b/include/linux/percpu-rwsem.h
index 5fda40f97fe9..36b942b67b7d 100644
--- a/include/linux/percpu-rwsem.h
+++ b/include/linux/percpu-rwsem.h
@@ -121,9 +121,15 @@ static inline void percpu_up_read(struct percpu_rw_semaphore *sem)
 	preempt_enable();
 }
 
+extern bool percpu_is_read_locked(struct percpu_rw_semaphore *);
 extern void percpu_down_write(struct percpu_rw_semaphore *);
 extern void percpu_up_write(struct percpu_rw_semaphore *);
 
+static inline bool percpu_is_write_locked(struct percpu_rw_semaphore *sem)
+{
+	return atomic_read(&sem->block);
+}
+
 extern int __percpu_init_rwsem(struct percpu_rw_semaphore *,
 				const char *, struct lock_class_key *);
 
diff --git a/kernel/locking/percpu-rwsem.c b/kernel/locking/percpu-rwsem.c
index 5fe4c5495ba3..213d114fb025 100644
--- a/kernel/locking/percpu-rwsem.c
+++ b/kernel/locking/percpu-rwsem.c
@@ -192,6 +192,12 @@ EXPORT_SYMBOL_GPL(__percpu_down_read);
 	__sum;								\
 })
 
+bool percpu_is_read_locked(struct percpu_rw_semaphore *sem)
+{
+	return per_cpu_sum(*sem->read_count) != 0;
+}
+EXPORT_SYMBOL_GPL(percpu_is_read_locked);
+
 /*
  * Return true if the modular sum of the sem->read_count per-CPU variable is
  * zero.  If this sum is zero, then it is stable due to the fact that if any
-- 
2.37.0.rc0.161.g10f37bed90-goog