Hi Mike,
Thu, Jul 23, 2020 at 06:55:47PM +0800, Mike Leach wrote:
Hi Tingwei,
On Thu, 23 Jul 2020 at 05:28, Tingwei Zhang tingwei@codeaurora.org wrote:
When coresight device is in an active session, driver module of that device should not be removed. Use try_get_module() in coresight_grab_device() to prevent module to be unloaded.
Signed-off-by: Tingwei Zhang tingwei@codeaurora.org
drivers/hwtracing/coresight/coresight.c | 27 +++++++++++++++++++++---- 1 file changed, 23 insertions(+), 4 deletions(-)
diff --git a/drivers/hwtracing/coresight/coresight.c
b/drivers/hwtracing/coresight/coresight.c
index b7151c5f81b1..17bc76ea86ae 100644 --- a/drivers/hwtracing/coresight/coresight.c +++ b/drivers/hwtracing/coresight/coresight.c @@ -640,7 +640,7 @@ struct coresight_device
*coresight_get_sink_by_id(u32 id)
- don't appear on the trace path, they should be handled along with
the
- the master device.
*/ -static void coresight_grab_device(struct coresight_device *csdev) +static int coresight_grab_device(struct coresight_device *csdev) { int i;
@@ -648,10 +648,25 @@ static void coresight_grab_device(struct
coresight_device *csdev)
struct coresight_device *child; child = csdev->pdata->conns[i].child_dev;
if (child && child->type == CORESIGHT_DEV_TYPE_HELPER)
if (child && child->type == CORESIGHT_DEV_TYPE_HELPER) {if(!try_module_get(child->dev.parent->driver->owner))
goto err; pm_runtime_get_sync(child->dev.parent);} }if (!try_module_get(csdev->dev.parent->driver->owner))goto err; pm_runtime_get_sync(csdev->dev.parent);return 0;+err:
for (i--; i >= 0; i--) {struct coresight_device *child;child = csdev->pdata->conns[i].child_dev;if (child && child->type == CORESIGHT_DEV_TYPE_HELPER)pm_runtime_put(child->dev.parent);}return -ENODEV;}
/* @@ -663,12 +678,15 @@ static void coresight_drop_device(struct
coresight_device *csdev)
int i; pm_runtime_put(csdev->dev.parent);
module_put(csdev->dev.parent->driver->owner); for (i = 0; i < csdev->pdata->nr_outport; i++) { struct coresight_device *child; child = csdev->pdata->conns[i].child_dev;
if (child && child->type == CORESIGHT_DEV_TYPE_HELPER)
if (child && child->type == CORESIGHT_DEV_TYPE_HELPER) { pm_runtime_put(child->dev.parent);module_put(child->dev.parent->driver->owner);} }}
@@ -721,7 +739,8 @@ static int _coresight_build_path(struct
coresight_device *csdev,
if (!node) return -ENOMEM;
coresight_grab_device(csdev);
if (coresight_grab_device(csdev))return -ENODEV; node->csdev = csdev; list_add(&node->link, path);-- The Qualcomm Innovation Center, Inc. is a member of the Code Aurora
Forum,
a Linux Foundation Collaborative Project
The CTI devices are associated with other coresight components using csdev->ect_dev; These are not handled in the main linear trace path as these have a star topology interlinking all components. However, when a component has an associated ect_dev then is enabled at the same time as the other component is enabled.
So a module_get/put will be needed for this association to prevent the CTI being removed while a trace session is active. I suggest in coresight.c : coresight_control_assoc_ectdev()
In module unload process, devices of that module will be removed. In this case, cti_remove() is called on all cti device when unloading cti module. All cti connections is cleaned at that time. csdev->ect_dev is set to NULL. coresight_control_assoc_ectdev() will return since since ect_csdev is NULL.
I think we are safe without holding module reference since cti driver has done a pretty good job on clean up.
Let me know if you still think we need hold the module reference.
Thanks, Tingwei
Regards
Mike
-- Mike Leach Principal Engineer, ARM Ltd. Manchester Design Centre. UK
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