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patch "intel_th: Fix a deadlock in modprobing" added to char-misc-next

PATCH [email protected] 1 participant 1 message Jul 15, 2016

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This is a note to let you know that I've just added the patch titled

intel_th: Fix a deadlock in modprobing

to my char-misc git tree which can be found at
git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/char-misc.git
in the char-misc-next branch.

The patch will show up in the next release of the linux-next tree (usually sometime within the next 24 hours during the week.)

The patch will also be merged in the next major kernel release during the merge window.

If you have any questions about this process, please let me know.

Quoted 1 line

From a36aa80f3cb2540fb1dbad6240852de4365a2e82 Mon Sep 17 00:00:00 2001

From: Alexander Shishkin <[email protected]>
Date: Thu, 30 Jun 2016 11:51:44 +0300
Subject: 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 <[email protected]>
Cc <[email protected]> # 4.4.x-
---
 drivers/hwtracing/intel_th/core.c     | 35 ++++++++++++++++++++++++++++++++++-
 drivers/hwtracing/intel_th/intel_th.h |  3 +++
 2 files changed, 37 insertions(+), 1 deletion(-)
drivers/hwtracing/intel_th/core.c +34 -1
index 1be543e8e42f..0b112ae689bf 100644
@@ -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]);
drivers/hwtracing/intel_th/intel_th.h +3 -0
index 0df22e30673d..04828482600b 100644
@@ -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
Signature · 1 line
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