[SCSI] add execute_in_process_context() API

We have several points in the SCSI stack (primarily for our device
functions) where we need to guarantee process context, but (given the
place where the last reference was released) we cannot guarantee this.

This API gets around the issue by executing the function directly if
the caller has process context, but scheduling a workqueue to execute
in process context if the caller doesn't have it.

Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>

diff --git a/include/linux/workqueue.h b/include/linux/workqueue.h
index 86b1113002319b5b9db5f765426d3ef2a35c687d..957c21c16d62370a9e158336a5981682d6f7625f 100644 (file)
--- a/include/linux/workqueue.h
+++ b/include/linux/workqueue.h
@@ -20,6 +20,10 @@ struct work_struct {
        struct timer_list timer;
 };
 
+struct execute_work {
+       struct work_struct work;
+};
+
 #define __WORK_INITIALIZER(n, f, d) {                          \
         .entry = { &(n).entry, &(n).entry },                   \
        .func = (f),                                            \
@@ -74,6 +78,8 @@ extern void init_workqueues(void);
 void cancel_rearming_delayed_work(struct work_struct *work);
 void cancel_rearming_delayed_workqueue(struct workqueue_struct *,
                                       struct work_struct *);
+int execute_in_process_context(void (*fn)(void *), void *,
+                              struct execute_work *);
 
 /*
  * Kill off a pending schedule_delayed_work().  Note that the work callback

diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index b052e2c4c71053720e87606e20924cfec5f3f27c..e9e464a903761b8dd5134bfa2ce20a68995da0e7 100644 (file)
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -27,6 +27,7 @@
 #include <linux/cpu.h>
 #include <linux/notifier.h>
 #include <linux/kthread.h>
+#include <linux/hardirq.h>
 
 /*
  * The per-CPU workqueue (if single thread, we always use the first
@@ -476,6 +477,34 @@ void cancel_rearming_delayed_work(struct work_struct *work)
 }
 EXPORT_SYMBOL(cancel_rearming_delayed_work);
 
+/**
+ * execute_in_process_context - reliably execute the routine with user context
+ * @fn:                the function to execute
+ * @data:      data to pass to the function
+ * @ew:                guaranteed storage for the execute work structure (must
+ *             be available when the work executes)
+ *
+ * Executes the function immediately if process context is available,
+ * otherwise schedules the function for delayed execution.
+ *
+ * Returns:    0 - function was executed
+ *             1 - function was scheduled for execution
+ */
+int execute_in_process_context(void (*fn)(void *data), void *data,
+                              struct execute_work *ew)
+{
+       if (!in_interrupt()) {
+               fn(data);
+               return 0;
+       }
+
+       INIT_WORK(&ew->work, fn, data);
+       schedule_work(&ew->work);
+
+       return 1;
+}
+EXPORT_SYMBOL_GPL(execute_in_process_context);
+
 int keventd_up(void)
 {
        return keventd_wq != NULL;