From: Mathieu Poirier <mathieu.poirier@linaro.org>
To: Bjorn Andersson <bjorn.andersson@linaro.org>
Cc: Andy Gross <agross@kernel.org>, Ohad Ben-Cohen <ohad@wizery.com>,
linux-arm-msm@vger.kernel.org, linux-remoteproc@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v4 1/4] remoteproc: Traverse rproc_list under RCU read lock
Date: Mon, 23 Mar 2020 15:52:05 -0600 [thread overview]
Message-ID: <20200323215205.GA30464@xps15> (raw)
In-Reply-To: <20200310063817.3344712-2-bjorn.andersson@linaro.org>
On Mon, Mar 09, 2020 at 11:38:14PM -0700, Bjorn Andersson wrote:
> 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();
> +
Please add linuc/rculist.h to include the RCU API. With that:
Reviewed-by: Mathieu Poirier <mathieu.poirier@linaro.org>
> device_del(&rproc->dev);
>
> return 0;
> --
> 2.24.0
>
next prev parent reply other threads:[~2020-03-23 21:52 UTC|newest]
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 ` [PATCH v4 1/4] remoteproc: Traverse rproc_list under RCU read lock Bjorn Andersson
2020-03-10 13:41 ` Arnaud POULIQUEN
2020-03-10 16:20 ` Bjorn Andersson
2020-03-23 21:52 ` Mathieu Poirier [this message]
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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