Message-ID: <544AF3FB.5000604@BlueTreble.com>
Date: Fri, 24 Oct 2014 19:51:07 -0500
From: Jim Nasby <Jim.Nasby@BlueTreble.com>
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To: Pg Hackers <pgsql-hackers@postgresql.org>
Subject: Comment patch for bgworker.c
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The comment for the BackgroundWorkerSlot structure tripped me up reviewing Robert's background worker patch; it made it clear that you need to use a memory barrier before setting in_use, but normally you'd never need to worry about that because RegisterDynamicBackgroundWorker() handles it for you. Patch adds a comment to that effect.
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Jim Nasby, Data Architect, Blue Treble Consulting
Data in Trouble? Get it in Treble! http://BlueTreble.com

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diff --git a/src/backend/postmaster/bgworker.c b/src/backend/postmaster/bgworker.c
index 85a3b3a..e81dbc1 100644
--- a/src/backend/postmaster/bgworker.c
+++ b/src/backend/postmaster/bgworker.c
@@ -55,7 +55,8 @@ slist_head	BackgroundWorkerList = SLIST_STATIC_INIT(BackgroundWorkerList);
  * responsibility of the postmaster.  Regular backends may no longer modify it,
  * but the postmaster may examine it.  Thus, a backend initializing a slot
  * must fully initialize the slot - and insert a write memory barrier - before
- * marking it as in use.
+ * marking it as in use. Note that RegisterDynamicBackgroundWorker() handles
+ * in_use correctly for you.
  *
  * As an exception, however, even when the slot is in use, regular backends
  * may set the 'terminate' flag for a slot, telling the postmaster not

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