workqueue: add documentation

[deliverable/linux.git] / kernel / workqueue.c

diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index a2dccfca03ba7f122532f28519e134a4c63a92e5..f77afd93922968d0c216bee148c0f10ed0ccaa72 100644 (file)
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -1,19 +1,26 @@
 /*
- * linux/kernel/workqueue.c
+ * kernel/workqueue.c - generic async execution with shared worker pool
  *
- * Generic mechanism for defining kernel helper threads for running
- * arbitrary tasks in process context.
+ * Copyright (C) 2002          Ingo Molnar
  *
- * Started by Ingo Molnar, Copyright (C) 2002
+ *   Derived from the taskqueue/keventd code by:
+ *     David Woodhouse <dwmw2@infradead.org>
+ *     Andrew Morton
+ *     Kai Petzke <wpp@marie.physik.tu-berlin.de>
+ *     Theodore Ts'o <tytso@mit.edu>
  *
- * Derived from the taskqueue/keventd code by:
+ * Made to use alloc_percpu by Christoph Lameter.
  *
- *   David Woodhouse <dwmw2@infradead.org>
- *   Andrew Morton
- *   Kai Petzke <wpp@marie.physik.tu-berlin.de>
- *   Theodore Ts'o <tytso@mit.edu>
+ * Copyright (C) 2010          SUSE Linux Products GmbH
+ * Copyright (C) 2010          Tejun Heo <tj@kernel.org>
  *
- * Made to use alloc_percpu by Christoph Lameter.
+ * This is the generic async execution mechanism.  Work items as are
+ * executed in process context.  The worker pool is shared and
+ * automatically managed.  There is one worker pool for each CPU and
+ * one extra for works which are better served by workers which are
+ * not bound to any specific CPU.
+ *
+ * Please read Documentation/workqueue.txt for details.
  */
 
 #include <linux/module.h>
@@ -35,6 +42,9 @@
 #include <linux/lockdep.h>
 #include <linux/idr.h>
 
+#define CREATE_TRACE_POINTS
+#include <trace/events/workqueue.h>
+
 #include "workqueue_sched.h"
 
 enum {
@@ -196,7 +206,7 @@ typedef cpumask_var_t mayday_mask_t;
        cpumask_test_and_set_cpu((cpu), (mask))
 #define mayday_clear_cpu(cpu, mask)            cpumask_clear_cpu((cpu), (mask))
 #define for_each_mayday_cpu(cpu, mask)         for_each_cpu((cpu), (mask))
-#define alloc_mayday_mask(maskp, gfp)          alloc_cpumask_var((maskp), (gfp))
+#define alloc_mayday_mask(maskp, gfp)          zalloc_cpumask_var((maskp), (gfp))
 #define free_mayday_mask(mask)                 free_cpumask_var((mask))
 #else
 typedef unsigned long mayday_mask_t;
@@ -1808,7 +1818,13 @@ __acquires(&gcwq->lock)
        work_clear_pending(work);
        lock_map_acquire(&cwq->wq->lockdep_map);
        lock_map_acquire(&lockdep_map);
+       trace_workqueue_execute_start(work);
        f(work);
+       /*
+        * While we must be careful to not use "work" after this, the trace
+        * point will only record its address.
+        */
+       trace_workqueue_execute_end(work);
        lock_map_release(&lockdep_map);
        lock_map_release(&cwq->wq->lockdep_map);
 
@@ -3558,8 +3574,7 @@ static int __init init_workqueues(void)
                spin_lock_init(&gcwq->lock);
                INIT_LIST_HEAD(&gcwq->worklist);
                gcwq->cpu = cpu;
-               if (cpu == WORK_CPU_UNBOUND)
-                       gcwq->flags |= GCWQ_DISASSOCIATED;
+               gcwq->flags |= GCWQ_DISASSOCIATED;
 
                INIT_LIST_HEAD(&gcwq->idle_list);
                for (i = 0; i < BUSY_WORKER_HASH_SIZE; i++)
@@ -3583,6 +3598,8 @@ static int __init init_workqueues(void)
                struct global_cwq *gcwq = get_gcwq(cpu);
                struct worker *worker;
 
+               if (cpu != WORK_CPU_UNBOUND)
+                       gcwq->flags &= ~GCWQ_DISASSOCIATED;
                worker = create_worker(gcwq, true);
                BUG_ON(!worker);
                spin_lock_irq(&gcwq->lock);