intel_th: Hold output driver module reference while capture is active

Right now it's possible to unload the output subdevice's driver while
the capture to this output is active. Prevent this by holding the
output driver's module reference.

Signed-off-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Reviewed-by: Laurent Fert <laurent.fert@intel.com>

diff --git a/drivers/hwtracing/intel_th/core.c b/drivers/hwtracing/intel_th/core.c
index 20339470c2c6ad55facfe94c74475c13f8d395ba..1be543e8e42fc12b0e2e3bb5d335497a2c917b4c 100644 (file)
--- a/drivers/hwtracing/intel_th/core.c
+++ b/drivers/hwtracing/intel_th/core.c
@@ -189,6 +189,9 @@ static int intel_th_output_activate(struct intel_th_device *thdev)
        if (!thdrv)
                return -ENODEV;
 
+       if (!try_module_get(thdrv->driver.owner))
+               return -ENODEV;
+
        if (thdrv->activate)
                return thdrv->activate(thdev);
 
@@ -209,6 +212,8 @@ static void intel_th_output_deactivate(struct intel_th_device *thdev)
                thdrv->deactivate(thdev);
        else
                intel_th_trace_disable(thdev);
+
+       module_put(thdrv->driver.owner);
 }
 
 static ssize_t active_show(struct device *dev, struct device_attribute *attr,