[RFC PATCH 1/3] workqueue: Add an interface to taint workqueue lockdep with reclaim

[Matthew Brost <matthew.brost@intel.com>]

Drivers often use workqueues that are in the reclaim path (e.g., DRM
scheduler workqueues). It is useful to teach lockdep that memory cannot
be allocated on these workqueues. Add an interface to taint workqueue
lockdep with reclaim.

Cc: Tejun Heo <tj@kernel.org>
Cc: Lai Jiangshan <jiangshanlai@gmail.com>
Signed-off-by: Matthew Brost <matthew.brost@intel.com>
---
 include/linux/workqueue.h | 19 +++++++++++++++++++
 kernel/workqueue.c        |  9 +++++++++
 2 files changed, 28 insertions(+)

diff --git a/include/linux/workqueue.h b/include/linux/workqueue.h
index dabc351cc127..954c7eb7e225 100644
--- a/include/linux/workqueue.h
+++ b/include/linux/workqueue.h
@@ -553,6 +553,25 @@ alloc_workqueue_lockdep_map(const char *fmt, unsigned int flags, int max_active,
 						1, lockdep_map, ##args))
 #endif
 
+
+#ifdef CONFIG_LOCKDEP
+/**
+ * taint_reclaim_workqueue - taint workqueue lockdep map with reclaim
+ * @wq: workqueue to taint with reclaim
+ * gfp: gfp taint
+ *
+ * Drivers often use workqueues that are in the reclaim path (e.g., DRM
+ * scheduler workqueues). It is useful to teach lockdep that memory cannot be
+ * allocated on these workqueues.
+ */
+extern void taint_reclaim_workqueue(struct workqueue_struct *wq, gfp_t gfp);
+#else
+static inline void taint_reclaim_workqueue(struct workqueue_struct *wq,
+					   gfp_t gfp)
+{
+}
+#endif
+
 /**
  * alloc_ordered_workqueue - allocate an ordered workqueue
  * @fmt: printf format for the name of the workqueue
diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index 45320e27a16c..fea410c20b71 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -5846,6 +5846,15 @@ alloc_workqueue_lockdep_map(const char *fmt, unsigned int flags,
 	return wq;
 }
 EXPORT_SYMBOL_GPL(alloc_workqueue_lockdep_map);
+
+void taint_reclaim_workqueue(struct workqueue_struct *wq, gfp_t gfp)
+{
+	fs_reclaim_acquire(gfp);
+	lock_map_acquire(wq->lockdep_map);
+	lock_map_release(wq->lockdep_map);
+	fs_reclaim_release(gfp);
+}
+EXPORT_SYMBOL_GPL(taint_reclaim_workqueue);
 #endif
 
 static bool pwq_busy(struct pool_workqueue *pwq)
-- 
2.34.1