intel_th: Fix a deadlock in modprobing

Driver initialization tries to request a hub (GTH) driver module from
its probe callback, resulting in a deadlock.

This patch solves the problem by adding a deferred work for requesting
the hub module.

Signed-off-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: <stable@vger.kernel.org> # 4.4.x-

diff --git a/drivers/hwtracing/intel_th/core.c b/drivers/hwtracing/intel_th/core.c
index 1be543e..0b112ae 100644 (file)
--- a/drivers/hwtracing/intel_th/core.c
+++ b/drivers/hwtracing/intel_th/core.c
@@ -465,6 +465,38 @@ static struct intel_th_subdevice {
        },
 };
 
+#ifdef CONFIG_MODULES
+static void __intel_th_request_hub_module(struct work_struct *work)
+{
+       struct intel_th *th = container_of(work, struct intel_th,
+                                          request_module_work);
+
+       request_module("intel_th_%s", th->hub->name);
+}
+
+static int intel_th_request_hub_module(struct intel_th *th)
+{
+       INIT_WORK(&th->request_module_work, __intel_th_request_hub_module);
+       schedule_work(&th->request_module_work);
+
+       return 0;
+}
+
+static void intel_th_request_hub_module_flush(struct intel_th *th)
+{
+       flush_work(&th->request_module_work);
+}
+#else
+static inline int intel_th_request_hub_module(struct intel_th *th)
+{
+       return -EINVAL;
+}
+
+static inline void intel_th_request_hub_module_flush(struct intel_th *th)
+{
+}
+#endif /* CONFIG_MODULES */
+
 static int intel_th_populate(struct intel_th *th, struct resource *devres,
                             unsigned int ndevres, int irq)
 {
@@ -535,7 +567,7 @@ static int intel_th_populate(struct intel_th *th, struct resource *devres,
                /* need switch driver to be loaded to enumerate the rest */
                if (subdev->type == INTEL_TH_SWITCH && !req) {
                        th->hub = thdev;
-                       err = request_module("intel_th_%s", subdev->name);
+                       err = intel_th_request_hub_module(th);
                        if (!err)
                                req++;
                }
@@ -652,6 +684,7 @@ void intel_th_free(struct intel_th *th)
 {
        int i;
 
+       intel_th_request_hub_module_flush(th);
        for (i = 0; i < TH_SUBDEVICE_MAX; i++)
                if (th->thdev[i] != th->hub)
                        intel_th_device_remove(th->thdev[i]);

diff --git a/drivers/hwtracing/intel_th/intel_th.h b/drivers/hwtracing/intel_th/intel_th.h
index 0df22e3..0482848 100644 (file)
--- a/drivers/hwtracing/intel_th/intel_th.h
+++ b/drivers/hwtracing/intel_th/intel_th.h
@@ -205,6 +205,9 @@ struct intel_th {
 
        int                     id;
        int                     major;
+#ifdef CONFIG_MODULES
+       struct work_struct      request_module_work;
+#endif /* CONFIG_MODULES */
 #ifdef CONFIG_INTEL_TH_DEBUG
        struct dentry           *dbg;
 #endif