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Message-ID: <1941b7e2-be7c-9c4c-8505-c0fd05910e9a@gmail.com>
Date: Sat, 18 Mar 2023 18:00:01 +0300
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Subject: Re: BF mamba failure
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To: Tom Lane <tgl@sss.pgh.pa.us>, Amit Kapila <amit.kapila16@gmail.com>
Cc: PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>,
 Peter Smith <smithpb2250@gmail.com>
References: 
 <CAA4eK1KxuMVyAryz_Vk5yq3ejgKYcL6F45Hj9ZnMNBS-g+PuZg@mail.gmail.com>
 <341870.1679113563@sss.pgh.pa.us>
From: Alexander Lakhin <exclusion@gmail.com>
In-Reply-To: <341870.1679113563@sss.pgh.pa.us>
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Hi,

18.03.2023 07:26, Tom Lane wrote:
> Amit Kapila<amit.kapila16@gmail.com>  writes:
>> Peter Smith has recently reported a BF failure [1]. AFAICS, the call
>> stack of failure [2] is as follows:
> Note the assertion report a few lines further up:
>
> TRAP: failed Assert("pg_atomic_read_u32(&entry_ref->shared_entry->refcount) == 0"), File: "pgstat_shmem.c", Line: 560, PID: 25004

This assertion failure can be reproduced easily with the attached patch:
============== running regression test queries        ==============
test oldest_xmin                  ... ok           55 ms
test oldest_xmin                  ... FAILED (test process exited with exit code 1)      107 ms
test oldest_xmin                  ... FAILED (test process exited with exit code 1)        8 ms
============== shutting down postmaster               ==============

contrib/test_decoding/output_iso/log/postmaster.log contains:
TRAP: failed Assert("pg_atomic_read_u32(&entry_ref->shared_entry->refcount) == 0"), File: "pgstat_shmem.c", Line: 561, 
PID: 456844

With the sleep placed above Assert(entry_ref->shared_entry->dropped) this Assert fails too.

Best regards,
Alexander
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<html>
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  <body>
    <div class="moz-cite-prefix">Hi,<br>
      <br>
      18.03.2023 07:26, Tom Lane wrote:<br>
    </div>
    <blockquote type="cite" cite="mid:341870.1679113563@sss.pgh.pa.us">
      <pre class="moz-quote-pre" wrap="">Amit Kapila <a class="moz-txt-link-rfc2396E" href="mailto:amit.kapila16@gmail.com">&lt;amit.kapila16@gmail.com&gt;</a> writes:
</pre>
      <blockquote type="cite">
        <pre class="moz-quote-pre" wrap="">Peter Smith has recently reported a BF failure [1]. AFAICS, the call
stack of failure [2] is as follows:
</pre>
      </blockquote>
      <pre class="moz-quote-pre" wrap="">
Note the assertion report a few lines further up:

TRAP: failed Assert("pg_atomic_read_u32(&amp;entry_ref-&gt;shared_entry-&gt;refcount) == 0"), File: "pgstat_shmem.c", Line: 560, PID: 25004
</pre>
    </blockquote>
    <br>
    This assertion failure can be reproduced easily with the attached
    patch:<br>
    <span style="font-family:monospace"><span
        style="color:#000000;background-color:#ffffff;">==============
        running regression test queries        ==============
      </span><br>
      test oldest_xmin                  ... ok           55 ms
      <br>
      test oldest_xmin                  ... FAILED (test process exited
      with exit code 1)      107 ms
      <br>
      test oldest_xmin                  ... FAILED (test process exited
      with exit code 1)        8 ms
      <br>
      ============== shutting down postmaster
                    ==============<br>
      <br>
    </span>contrib/test_decoding/output_iso/log/postmaster.log contains:<br>
    <span style="font-family:monospace">TRAP: failed
      Assert("pg_atomic_read_u32(&amp;entry_ref-&gt;shared_entry-&gt;refcount)
      == 0"), File: "pgstat_shmem.c", Line: 561, PID: 456844<br>
    </span><br>
    With the sleep placed above
    Assert(entry_ref-&gt;shared_entry-&gt;dropped) this Assert fails
    too.<br>
    <br>
    Best regards,<br>
    Alexander<br>
  </body>
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