On 8/29/2023 12:54 AM, Bartosz Golaszewski wrote:
Checking for the availability of SCM bridge can happen from any context.
It's only by chance that we haven't run into concurrency issues but with
the upcoming SHM Bridge driver that will be initiated at the same
initcall level, we need to assure the assignment and readback of the
__scm pointer is atomic.
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@xxxxxxxxxx>
---
drivers/firmware/qcom_scm.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/drivers/firmware/qcom_scm.c b/drivers/firmware/qcom_scm.c
index 980fcfa20b9f..422de70faff8 100644
--- a/drivers/firmware/qcom_scm.c
+++ b/drivers/firmware/qcom_scm.c
@@ -1331,7 +1331,7 @@ static int qcom_scm_find_dload_address(struct device *dev, u64 *addr)
*/
bool qcom_scm_is_available(void)
{
- return !!__scm;
+ return !!READ_ONCE(__scm);
}
EXPORT_SYMBOL(qcom_scm_is_available);
@@ -1477,8 +1477,8 @@ static int qcom_scm_probe(struct platform_device *pdev)
if (ret)
return ret;
- __scm = scm;
- __scm->dev = &pdev->dev;
+ scm->dev = &pdev->dev;
+ WRITE_ONCE(__scm, scm);
In my opinion "__scm = scm;" assignment should be done at the end of
probe function success so that qcom_scm_is_available() return true only
when probe is completed.
Other changes may not be needed.
init_completion(&__scm->waitq_comp);
