Hello,
On Thu, Apr 11, 2013 at 11:30:53PM +0300, Michael S. Tsirkin wrote:
> Okay, so you are saying it's a false-positive?
Yeah, I think so. It didn't actually lock up, right? It it did,
our analysis upto this point is likely to be completely wrong.
> Want to send a patch so Or can try it out?
Hmmm... something like the following on the workqueue side (completely
untested).
diff --git a/include/linux/workqueue.h b/include/linux/workqueue.h
index 8afab27..899d470 100644
--- a/include/linux/workqueue.h
+++ b/include/linux/workqueue.h
@@ -466,14 +466,21 @@ static inline bool __deprecated flush_delayed_work_sync(struct delayed_work *dwo
}
#ifndef CONFIG_SMP
-static inline long work_on_cpu(unsigned int cpu, long (*fn)(void *), void *arg)
+static inline long work_on_cpu_nested(unsigned int cpu, long (*fn)(void *),
+ void *arg, int subclass)
{
return fn(arg);
}
#else
-long work_on_cpu(unsigned int cpu, long (*fn)(void *), void *arg);
+long work_on_cpu_nested(unsigned int cpu, long (*fn)(void *), void *arg,
+ int subclass);
#endif /* CONFIG_SMP */
+static inline long work_on_cpu(unsigned int cpu, long (*fn)(void *), void *arg)
+{
+ return work_on_cpu_nested(cpu, fn, arg, 0);
+}
+
#ifdef CONFIG_FREEZER
extern void freeze_workqueues_begin(void);
extern bool freeze_workqueues_busy(void);
diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index 81f2457..c2be670 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -3555,25 +3555,30 @@ static void work_for_cpu_fn(struct work_struct *work)
}
/**
- * work_on_cpu - run a function in user context on a particular cpu
+ * work_on_cpu_nested - run a function in user context on a particular cpu
* @cpu: the cpu to run on
* @fn: the function to run
* @arg: the function arg
+ * @subclass: lockdep subclass
*
* This will return the value @fn returns.
* It is up to the caller to ensure that the cpu doesn't go offline.
* The caller must not hold any locks which would prevent @fn from completing.
+ *
+ * XXX: explain @subclass
*/
-long work_on_cpu(unsigned int cpu, long (*fn)(void *), void *arg)
+long work_on_cpu_nested(unsigned int cpu, long (*fn)(void *), void *arg,
+ int subclass)
{
struct work_for_cpu wfc = { .fn = fn, .arg = arg };
INIT_WORK_ONSTACK(&wfc.work, work_for_cpu_fn);
+ lock_set_subclass(&wfc.work.lockdep_map, subclass, _RET_IP_);
schedule_work_on(cpu, &wfc.work);
flush_work(&wfc.work);
return wfc.ret;
}
-EXPORT_SYMBOL_GPL(work_on_cpu);
+EXPORT_SYMBOL_GPL(work_on_cpu_nested);
#endif /* CONFIG_SMP */
#ifdef CONFIG_FREEZER
--
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