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From: Bjorn Andersson <bjorn.andersson@linaro.org>
To: Andy Gross <agross@kernel.org>,
	Bjorn Andersson <bjorn.andersson@linaro.org>,
	Ohad Ben-Cohen <ohad@wizery.com>
Cc: linux-arm-msm@vger.kernel.org, linux-remoteproc@vger.kernel.org,
	linux-kernel@vger.kernel.org,
	Mathieu Poirier <mathieu.poirier@linaro.org>
Subject: [PATCH v4 1/4] remoteproc: Traverse rproc_list under RCU read lock
Date: Mon,  9 Mar 2020 23:38:14 -0700
Message-ID: <20200310063817.3344712-2-bjorn.andersson@linaro.org> (raw)
In-Reply-To: <20200310063817.3344712-1-bjorn.andersson@linaro.org>

In order to be able to traverse the mostly read-only rproc_list without
locking during panic migrate traversal to be done under rcu_read_lock().

Mutual exclusion for modifications of the list continues to be handled
by the rproc_list_mutex and a synchronization point is added before
releasing objects that are popped from the list.

Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
---

Change v3:
- New patch

 drivers/remoteproc/remoteproc_core.c | 13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/drivers/remoteproc/remoteproc_core.c b/drivers/remoteproc/remoteproc_core.c
index 097f33e4f1f3..f0a77c30c6b1 100644
--- a/drivers/remoteproc/remoteproc_core.c
+++ b/drivers/remoteproc/remoteproc_core.c
@@ -1854,8 +1854,8 @@ struct rproc *rproc_get_by_phandle(phandle phandle)
 	if (!np)
 		return NULL;
 
-	mutex_lock(&rproc_list_mutex);
-	list_for_each_entry(r, &rproc_list, node) {
+	rcu_read_lock();
+	list_for_each_entry_rcu(r, &rproc_list, node) {
 		if (r->dev.parent && r->dev.parent->of_node == np) {
 			/* prevent underlying implementation from being removed */
 			if (!try_module_get(r->dev.parent->driver->owner)) {
@@ -1868,7 +1868,7 @@ struct rproc *rproc_get_by_phandle(phandle phandle)
 			break;
 		}
 	}
-	mutex_unlock(&rproc_list_mutex);
+	rcu_read_unlock();
 
 	of_node_put(np);
 
@@ -1925,7 +1925,7 @@ int rproc_add(struct rproc *rproc)
 
 	/* expose to rproc_get_by_phandle users */
 	mutex_lock(&rproc_list_mutex);
-	list_add(&rproc->node, &rproc_list);
+	list_add_rcu(&rproc->node, &rproc_list);
 	mutex_unlock(&rproc_list_mutex);
 
 	return 0;
@@ -2140,9 +2140,12 @@ int rproc_del(struct rproc *rproc)
 
 	/* the rproc is downref'ed as soon as it's removed from the klist */
 	mutex_lock(&rproc_list_mutex);
-	list_del(&rproc->node);
+	list_del_rcu(&rproc->node);
 	mutex_unlock(&rproc_list_mutex);
 
+	/* Ensure that no readers of rproc_list are still active */
+	synchronize_rcu();
+
 	device_del(&rproc->dev);
 
 	return 0;
-- 
2.24.0


  reply index

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-03-10  6:38 [PATCH v4 0/4] remoteproc: Panic handling Bjorn Andersson
2020-03-10  6:38 ` Bjorn Andersson [this message]
2020-03-10 13:41   ` [PATCH v4 1/4] remoteproc: Traverse rproc_list under RCU read lock Arnaud POULIQUEN
2020-03-10 16:20     ` Bjorn Andersson
2020-03-23 21:52   ` Mathieu Poirier
2020-03-10  6:38 ` [PATCH v4 2/4] remoteproc: Introduce "panic" callback in ops Bjorn Andersson
2020-03-23 22:29   ` Mathieu Poirier
2020-03-23 22:33   ` Mathieu Poirier
2020-03-10  6:38 ` [PATCH v4 3/4] remoteproc: qcom: q6v5: Add common panic handler Bjorn Andersson
2020-03-23 22:36   ` Mathieu Poirier
2020-03-10  6:38 ` [PATCH v4 4/4] remoteproc: qcom: Introduce panic handler for PAS and ADSP Bjorn Andersson
2020-03-23 22:45   ` Mathieu Poirier

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