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authorSiri Hansen <[email protected]>2018-09-07 12:16:00 +0200
committerSiri Hansen <[email protected]>2018-09-07 12:16:00 +0200
commit3b50bb697121de96d03deffcd65ed5859de86558 (patch)
treef932ca5be98cdc5521ca48cf453bf51e273c893a /system/doc
parent5801fcb2b36e04c433dcf0b90a8c47b86e34fc07 (diff)
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[supervisor] Add warning about race condition
ERL-724: "During a 'gentle' shutdown, supervisors unlink from their children before sending shutdown signals to them. This can lead to a race condition in supervision trees, when the timeout for gentle shutdown of a parent supervisor expires and it kills a child supervisor that has just unlinked from a child of its own, leaving the child supervisor's own child still running after its supervisor is killed." This commit adds a warning about this in the documentation.
Diffstat (limited to 'system/doc')
-rw-r--r--system/doc/design_principles/sup_princ.xml9
1 files changed, 7 insertions, 2 deletions
diff --git a/system/doc/design_principles/sup_princ.xml b/system/doc/design_principles/sup_princ.xml
index 06ca44a9f6..a2e0d95408 100644
--- a/system/doc/design_principles/sup_princ.xml
+++ b/system/doc/design_principles/sup_princ.xml
@@ -312,12 +312,17 @@ child_spec() = #{id => child_id(), % mandatory
signal back. If no exit signal is received within
the specified time, the child process is unconditionally
terminated using <c>exit(Child, kill)</c>.</item>
- <item>If the child process is another supervisor, it is to be
+ <item>If the child process is another supervisor, it must be
set to <c>infinity</c> to give the subtree enough time to
shut down. It is also allowed to set it to <c>infinity</c>,
- if the child process is a worker. See the warning below:</item>
+ if the child process is a worker. See the warning below:</item>
</list>
<warning>
+ <p>Setting the shutdown time to anything other
+ than <c>infinity</c> for a child of type <c>supervisor</c>
+ can cause a race condition where the child in question
+ unlinks its own children, but fails to terminate them
+ before it is killed.</p>
<p>Be careful when setting the shutdown time to
<c>infinity</c> when the child process is a worker. Because, in this
situation, the termination of the supervision tree depends on the