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From: "Derrick Stolee via GitGitGadget" <gitgitgadget@gmail.com>
To: git@vger.kernel.org
Cc: Junio C Hamano <gitster@pobox.com>,
	Derrick Stolee <dstolee@microsoft.com>
Subject: [PATCH 1/1] upload-pack: fix race condition in error messages
Date: Tue, 27 Aug 2019 18:43:29 -0700 (PDT)	[thread overview]
Message-ID: <5c313aba7e97cb93e7d07f6d5dfaf0febe8a2f8b.1566956608.git.gitgitgadget@gmail.com> (raw)
In-Reply-To: <pull.324.git.gitgitgadget@gmail.com>

From: Derrick Stolee <dstolee@microsoft.com>

Test t5516-fetch-push.sh has a test 'deny fetch unreachable SHA1,
allowtipsha1inwant=true' that checks stderr for a specific error
string from the remote. In some build environments the error sent
over the remote connection gets mingled with the error from the
die() statement. Since both signals are being output to the same
file descriptor (but from parent and child processes), the output
we are matching with grep gets split.

To reduce the risk of this failure, follow this process instead:

1. Write an error message to stderr.
2. Write an error message across the connection.
3. exit(1).

This reorders the events so the error is written entirely before
the client receives a message from the remote, removing the race
condition.

Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
---
 upload-pack.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/upload-pack.c b/upload-pack.c
index 222cd3ad89..b0d3e028d1 100644
--- a/upload-pack.c
+++ b/upload-pack.c
@@ -613,11 +613,12 @@ static void check_non_tip(struct object_array *want_obj,
 	for (i = 0; i < want_obj->nr; i++) {
 		struct object *o = want_obj->objects[i].item;
 		if (!is_our_ref(o)) {
+			warning("git upload-pack: not our ref %s",
+				oid_to_hex(&o->oid));
 			packet_writer_error(writer,
 					    "upload-pack: not our ref %s",
 					    oid_to_hex(&o->oid));
-			die("git upload-pack: not our ref %s",
-			    oid_to_hex(&o->oid));
+			exit(1);
 		}
 	}
 }
-- 
gitgitgadget

  reply	other threads:[~2019-08-28  1:43 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-08-28  1:43 [PATCH 0/1] upload-pack: fix race condition in t5516 Derrick Stolee via GitGitGadget
2019-08-28  1:43 ` Derrick Stolee via GitGitGadget [this message]
2019-08-28  9:34   ` [PATCH 1/1] upload-pack: fix race condition in error messages SZEDER Gábor
2019-08-28 14:54     ` Jeff King
2019-08-28 15:39       ` Jeff King
2019-08-28 16:15         ` SZEDER Gábor
2019-08-29 12:58           ` Derrick Stolee
2019-08-29 14:13             ` Jeff King
2019-08-29 14:27               ` Derrick Stolee
2019-08-29 14:38                 ` Jeff King
2019-08-29 21:58                   ` SZEDER Gábor
2019-08-29 22:06                     ` SZEDER Gábor
2019-08-30 12:10                       ` SZEDER Gábor
2019-09-04  5:04                         ` Jeff King
2019-09-10 12:08                           ` SZEDER Gábor

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