workqueue: devres: Add device-managed allocate workqueue

Add a Resource-managed version of alloc_workqueue() to fix common
problem of drivers mixing devm() calls with destroy_workqueue.  Such
naive and discouraged driver approach leads to difficult to debug bugs
when the driver:

1. Allocates workqueue in standard way and destroys it in driver
   remove() callback,
2. Sets work struct with devm_work_autocancel(),
3. Registers interrupt handler with devm_request_threaded_irq().

Which leads to following unbind/removal path:

1. destroy_workqueue() via driver remove(),
   Any interrupt coming now would still execute the interrupt handler,
   which queues work on destroyed workqueue.
2. devm_irq_release(),
3. devm_work_drop() -> cancel_work_sync() on destroyed workqueue.

devm_alloc_workqueue() has two benefits:
1. Solves above problem of mix-and-match devres and non-devres code in
   driver,
2. Simplify any sane drivers which were correctly using
   alloc_workqueue() + devm_add_action_or_reset().

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@oss.qualcomm.com>
Acked-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

diff --git a/Documentation/driver-api/driver-model/devres.rst b/Documentation/driver-api/driver-model/devres.rst
index 7d2b897d66fa95f1cd8cac7908948b012001e391..017fb155a5bc2515c264b9b018298e7cd14ef87d 100644 (file)
--- a/Documentation/driver-api/driver-model/devres.rst
+++ b/Documentation/driver-api/driver-model/devres.rst
@@ -464,3 +464,7 @@ SPI
 
 WATCHDOG
   devm_watchdog_register_device()
+
+WORKQUEUE
+  devm_alloc_workqueue()
+  devm_alloc_ordered_workqueue()

diff --git a/include/linux/workqueue.h b/include/linux/workqueue.h
index a4749f56398fd6cd721bcf6573918199c52f2cca..f8d235aef10dd863f0e6cbd9d19aeeecb516ac22 100644 (file)
--- a/include/linux/workqueue.h
+++ b/include/linux/workqueue.h
@@ -512,6 +512,26 @@ __printf(1, 4) struct workqueue_struct *
 alloc_workqueue_noprof(const char *fmt, unsigned int flags, int max_active, ...);
 #define alloc_workqueue(...)   alloc_hooks(alloc_workqueue_noprof(__VA_ARGS__))
 
+/**
+ * devm_alloc_workqueue - Resource-managed allocate a workqueue
+ * @dev: Device to allocate workqueue for
+ * @fmt: printf format for the name of the workqueue
+ * @flags: WQ_* flags
+ * @max_active: max in-flight work items, 0 for default
+ * @...: args for @fmt
+ *
+ * Resource managed workqueue, see alloc_workqueue() for details.
+ *
+ * The workqueue will be automatically destroyed on driver detach.  Typically
+ * this should be used in drivers already relying on devm interafaces.
+ *
+ * RETURNS:
+ * Pointer to the allocated workqueue on success, %NULL on failure.
+ */
+__printf(2, 5) struct workqueue_struct *
+devm_alloc_workqueue(struct device *dev, const char *fmt, unsigned int flags,
+                    int max_active, ...);
+
 #ifdef CONFIG_LOCKDEP
 /**
  * alloc_workqueue_lockdep_map - allocate a workqueue with user-defined lockdep_map
@@ -568,6 +588,8 @@ alloc_workqueue_lockdep_map(const char *fmt, unsigned int flags, int max_active,
  */
 #define alloc_ordered_workqueue(fmt, flags, args...)                   \
        alloc_workqueue(fmt, WQ_UNBOUND | __WQ_ORDERED | (flags), 1, ##args)
+#define devm_alloc_ordered_workqueue(dev, fmt, flags, args...)         \
+       devm_alloc_workqueue(dev, fmt, WQ_UNBOUND | __WQ_ORDERED | (flags), 1, ##args)
 
 #define create_workqueue(name)                                         \
        alloc_workqueue("%s", __WQ_LEGACY | WQ_MEM_RECLAIM | WQ_PERCPU, 1, (name))

diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index aeaec79bc09c4958e0841ebe1e33409a1d386427..19d20f3039d9e45adedab650bde3c409a99bfd44 100644 (file)
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -41,6 +41,7 @@
 #include <linux/mempolicy.h>
 #include <linux/freezer.h>
 #include <linux/debug_locks.h>
+#include <linux/device/devres.h>
 #include <linux/lockdep.h>
 #include <linux/idr.h>
 #include <linux/jhash.h>
@@ -5891,6 +5892,33 @@ struct workqueue_struct *alloc_workqueue_noprof(const char *fmt,
 }
 EXPORT_SYMBOL_GPL(alloc_workqueue_noprof);
 
+static void devm_workqueue_release(void *res)
+{
+       destroy_workqueue(res);
+}
+
+__printf(2, 5) struct workqueue_struct *
+devm_alloc_workqueue(struct device *dev, const char *fmt, unsigned int flags,
+                    int max_active, ...)
+{
+       struct workqueue_struct *wq;
+       va_list args;
+       int ret;
+
+       va_start(args, max_active);
+       wq = alloc_workqueue(fmt, flags, max_active, args);
+       va_end(args);
+       if (!wq)
+               return NULL;
+
+       ret = devm_add_action_or_reset(dev, devm_workqueue_release, wq);
+       if (ret)
+               return NULL;
+
+       return wq;
+}
+EXPORT_SYMBOL_GPL(devm_alloc_workqueue);
+
 #ifdef CONFIG_LOCKDEP
 __printf(1, 5)
 struct workqueue_struct *