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authorDavid Howells <dhowells@redhat.com>2009-11-19 18:10:53 +0000
committerDavid Howells <dhowells@redhat.com>2009-11-19 18:10:53 +0000
commit31ba99d304494cb28fa8671ccc769c5543e1165d (patch)
treeea2d839fb70798cf6a3b55ccc87f749e14e14f1d /Documentation/slow-work.txt
parent8fba10a42d191de612e60e7009c8f0313f90a9b3 (diff)
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SLOW_WORK: Allow the owner of a work item to determine if it is queued or not
Add a function (slow_work_is_queued()) to permit the owner of a work item to determine if the item is queued or not. The work item is counted as being queued if it is actually on the queue, not just if it is pending. If it is executing and pending, then it is not on the queue, but will rather be put back on the queue when execution finishes. This permits a caller to quickly work out if it may be able to put another, dependent work item on the queue behind it, or whether it will have to wait till that is finished. This can be used by CacheFiles to work out whether the creation a new object can be immediately deferred when it has to wait for an old object to be deleted, or whether a wait must take place. If a wait is necessary, then the slow-work thread can otherwise get blocked, preventing the deletion from taking place. Signed-off-by: David Howells <dhowells@redhat.com>
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diff --git a/Documentation/slow-work.txt b/Documentation/slow-work.txt
index f120238e70fe..0169c9d9dd16 100644
--- a/Documentation/slow-work.txt
+++ b/Documentation/slow-work.txt
@@ -144,6 +144,21 @@ from being taken away before it completes. module should almost certainly be
THIS_MODULE.
+================
+HELPER FUNCTIONS
+================
+
+The slow-work facility provides a function by which it can be determined
+whether or not an item is queued for later execution:
+
+ bool queued = slow_work_is_queued(struct slow_work *work);
+
+If it returns false, then the item is not on the queue (it may be executing
+with a requeue pending). This can be used to work out whether an item on which
+another depends is on the queue, thus allowing a dependent item to be queued
+after it.
+
+
===============
ITEM OPERATIONS
===============
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