File PR29474-debuginfod.patch of Package elfutils

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File PR29474-debuginfod.patch of Package elfutils

From 31d6b1fe74ab89138b4d256742997b730dc5cba8 Mon Sep 17 00:00:00 2001
From: "Frank Ch. Eigler" <fche@redhat.com>
Date: Mon, 15 Aug 2022 06:20:10 -0400
Subject: [PATCH] PR29474: debuginfod
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Previous code sometimes confused debuginfod with concurrent queries
targeting the same RPM.  One thread fetching & prefetching, the other
thread misinterpreted the sudden presence of its target file in the
fdcache as a mere unnecessary prefetch duplicate.  But if it was the
other thread's target file, previous code would -skip- it completely,
resulting in a 404 error.  New code allows the other thread to also
decompress the target file and return it, and still continue to its
own prefetching process for other files.

There's a performance trade-off here.  Another option would be for the
other thread to check the fdcache regularly and abort its own
prefetch/fetch/prefetch loop early in case of a sudden target file
hit.  That'd save CPU probably but it'd stop prefetching of later
segments of the input archive, which could save future time.

Automated testing is too time/load sensitive to attempt.  Confirmed
working with Martin's stress tester.

Reported-By: Martin Liška <mliska@suse.cz>
Signed-Off-By: Frank Ch. Eigler <fche@redhat.com>
---
 debuginfod/ChangeLog      | 6 ++++++
 debuginfod/debuginfod.cxx | 3 ++-
 2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/debuginfod/debuginfod.cxx b/debuginfod/debuginfod.cxx
index a089d0bd..9245be53 100644
--- a/debuginfod/debuginfod.cxx
+++ b/debuginfod/debuginfod.cxx
@@ -1742,7 +1742,8 @@ handle_buildid_r_match (bool internal_req_p,
       if ((r == 0) && (fn != b_source1)) // stage 1
         continue;
 
-      if (fdcache.probe (b_source0, fn)) // skip if already interned
+      if (fdcache.probe (b_source0, fn) && // skip if already interned
+          fn != b_source1) // but only if we'd just be prefetching, PR29474
         continue;
 
       // extract this file to a temporary file
-- 
2.37.1

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File PR29474-debuginfod.patch of Package elfutils

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