linux-kernel - [PATCH v6 2/3] workqueue: doc: Add a note saturating the system

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Message-Id: <20241008112458.49387-3-chenridong@huaweicloud.com>
Date: Tue,  8 Oct 2024 11:24:57 +0000
From: Chen Ridong <chenridong@...weicloud.com>
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Subject: [PATCH v6 2/3] workqueue: doc: Add a note saturating the system_wq is not permitted

From: Chen Ridong <chenridong@...wei.com>

If something is expected to generate large number of concurrent works,
it should utilize its own dedicated workqueue rather than system wq.
Because this may saturate system_wq and potentially block other's works.
eg, cgroup release work. Let's document this as a note.

Signed-off-by: Chen Ridong <chenridong@...wei.com>
---
 Documentation/core-api/workqueue.rst | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/Documentation/core-api/workqueue.rst b/Documentation/core-api/workqueue.rst
index 16f861c9791e..2b813f80ce39 100644
--- a/Documentation/core-api/workqueue.rst
+++ b/Documentation/core-api/workqueue.rst
@@ -357,6 +357,11 @@ Guidelines
   difference in execution characteristics between using a dedicated wq
   and a system wq.
 
+  Note: If something may generate more than @max_active outstanding
+  work items (do stress test your producers), it may saturate a system
+  wq and potentially lead to deadlock. It should utilize its own
+  dedicated workqueue rather than the system wq.
+
 * Unless work items are expected to consume a huge amount of CPU
   cycles, using a bound wq is usually beneficial due to the increased
   level of locality in wq operations and work item execution.
-- 
2.34.1