Re: ERROR: invalid spinlock number: 0

On Thu, Feb 11, 2021 at 11:30:13PM +0900, Fujii Masao wrote:
> Yes, so what about the attached patch?

I see.  So the first error triggering the spinlock error would cause
a transaction failure because the fallback implementation of atomics
uses a spinlock for this variable, and it may not initialized in this
code path.

> We didn't notice this issue long time because no regression test checks
> pg_stat_wal_receiver. So I included such test in the patch.

Moving that behind ready_to_display is fine by me seeing where the
initialization is done.  The test case is a good addition.

+    * Read "writtenUpto" without holding a spinlock. So it may not be
+    * consistent with other WAL receiver's shared variables protected by a
+    * spinlock. This is OK because that variable is used only for
+    * informational purpose and should not be used for data integrity checks.
It seems to me that the first two sentences of this comment should be
combined together.
--
Michael