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From: Ramsay Jones <ramsay@ramsayjones.plus.com>
To: Johannes Schindelin <Johannes.Schindelin@gmx.de>,
	Adam Dinwoodie <adam@dinwoodie.org>
Cc: "Jeff Hostetler via GitGitGadget" <gitgitgadget@gmail.com>,
	git@vger.kernel.org, "Eric Sunshine" <sunshine@sunshineco.com>,
	"Taylor Blau" <me@ttaylorr.com>,
	"Ævar Arnfjörð Bjarmason" <avarab@gmail.com>,
	"Jeff Hostetler" <git@jeffhostetler.com>,
	"Carlo Arenas" <carenas@gmail.com>,
	"Jeff Hostetler" <jeffhost@microsoft.com>
Subject: Re: [PATCH v2 7/7] t/helper/simple-ipc: convert test-simple-ipc to use start_bg_command
Date: Tue, 9 Nov 2021 18:53:39 +0000	[thread overview]
Message-ID: <dca03da9-5684-10c7-2315-2d10affd4f0a@ramsayjones.plus.com> (raw)
In-Reply-To: <nycvar.QRO.7.76.6.2111090051530.54@tvgsbejvaqbjf.bet>



On 08/11/2021 23:59, Johannes Schindelin wrote:
[snip]
> I had a look at this and could reproduce... partially. I only managed to
> make it fail every once in a while.
> 
> Digging deeper, it turns out that the `lstat()` call in
> `ipc_get_active_state()` does not receive an `st_mode` indicating a
> socket, but rather a file (in my tests, it was usually 0100644, but
> sometimes even 0100755).
> 
> The reason is, of course, that Cygwin _emulates_ Unix sockets. What is in
> the file system is just a special file, it is marked with the `system` bit
> (which only exists on Windows), and its contents start with the tell-tale
> `!<socket>`.
> 
> And as you might have guessed, there is a race going on between Cygwin
> writing that file _and_ flipping that `system` bit, and Git trying to
> access the Unix socket and encountering an unexpected file.
> 
> Now, why this only happens in your 32-bit setup, I have no idea.
> 
> In my tests, the following patch works around the issue. Could I ask you
> to test it in your environment?

Just FYI, I just tried the patch below (on 64-bit cygwin) and this test
now works fine for me. (well, run 5 times by hand - not with --stress).

This is on windows 10 21H1 and cygwin:

  $ uname -a
  CYGWIN_NT-10.0 satellite 3.3.2(0.341/5/3) 2021-11-08 16:55 x86_64 Cygwin
  $ 

[Yes, I updated last night!]

ATB,
Ramsay Jones

> -- snip --
> diff --git a/compat/simple-ipc/ipc-unix-socket.c
> b/compat/simple-ipc/ipc-unix-socket.c
> index 4e28857a0a..1c591b2adf 100644
> --- a/compat/simple-ipc/ipc-unix-socket.c
> +++ b/compat/simple-ipc/ipc-unix-socket.c
> @@ -36,6 +36,23 @@ enum ipc_active_state ipc_get_active_state(const char
> *path)
>  	}
> 
>  	/* also complain if a plain file is in the way */
> +#ifdef __CYGWIN__
> +	{
> +		static const int delay[] = { 1, 10, 20, 40, -1 };
> +		int i;
> +
> +		for (i = 0; S_ISREG(st.st_mode) && delay[i] > 0; i++) {
> +			/*
> +			 * Cygwin might still be in the process of marking the
> +			 * underlying file as a system file.
> +			 */
> +			sleep_millisec(delay[i]);
> +			if (lstat(path, &st) == -1)
> +				return IPC_STATE__INVALID_PATH;
> +		}
> +	}
> +#endif
> +
>  	if ((st.st_mode & S_IFMT) != S_IFSOCK)
>  		return IPC_STATE__INVALID_PATH;
> 
> -- snap --
> 
> FWIW it looks as if the loop might be a bit of an overkill, as I could not
> get the code to need more than a single one-millisecond sleep, but it's
> probably safer to just keep the delay loop in place as-is.
> 
> Ciao,
> Dscho
> 

  reply	other threads:[~2021-11-09 18:53 UTC|newest]

Thread overview: 66+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-09-15 20:36 [PATCH 0/7] Builtin FSMonitor Part 1 Jeff Hostetler via GitGitGadget
2021-09-15 20:36 ` [PATCH 1/7] trace2: fix memory leak of thread name Jeff Hostetler via GitGitGadget
2021-09-15 21:01   ` Junio C Hamano
2021-09-16  4:19     ` Taylor Blau
2021-09-16  5:35   ` Ævar Arnfjörð Bjarmason
2021-09-16  5:43     ` Taylor Blau
2021-09-16  8:01       ` Ævar Arnfjörð Bjarmason
2021-09-16 15:35         ` Jeff Hostetler
2021-09-16 15:47           ` Ævar Arnfjörð Bjarmason
2021-09-16 19:13         ` Junio C Hamano
2021-09-15 20:36 ` [PATCH 2/7] simple-ipc: preparations for supporting binary messages Jeff Hostetler via GitGitGadget
2021-09-15 20:43   ` Eric Sunshine
2021-09-17 16:52     ` Jeff Hostetler
2021-09-15 20:36 ` [PATCH 3/7] simple-ipc: move definition of ipc_active_state outside of ifdef Jeff Hostetler via GitGitGadget
2021-09-15 21:06   ` Junio C Hamano
2021-09-17 16:58     ` Jeff Hostetler
2021-09-18  7:03       ` Carlo Arenas
2021-09-20 15:51       ` Junio C Hamano
2021-09-15 20:36 ` [PATCH 4/7] simple-ipc/ipc-win32: add trace2 debugging Jeff Hostetler via GitGitGadget
2021-09-16  5:40   ` Ævar Arnfjörð Bjarmason
2021-09-17 17:27     ` Jeff Hostetler
2021-09-15 20:36 ` [PATCH 5/7] simple-ipc/ipc-win32: add Windows ACL to named pipe Jeff Hostetler via GitGitGadget
2021-09-16  5:47   ` Ævar Arnfjörð Bjarmason
2021-09-17 18:10     ` Jeff Hostetler
2021-09-17 19:14       ` Ævar Arnfjörð Bjarmason
2021-09-15 20:36 ` [PATCH 6/7] run-command: create start_bg_command Jeff Hostetler via GitGitGadget
2021-09-16  4:53   ` Taylor Blau
2021-09-16  4:58     ` Taylor Blau
2021-09-16  5:56   ` Ævar Arnfjörð Bjarmason
2021-09-15 20:36 ` [PATCH 7/7] t/helper/simple-ipc: convert test-simple-ipc to use start_bg_command Jeff Hostetler via GitGitGadget
2021-09-16  5:06   ` Taylor Blau
2021-09-17 19:41     ` Jeff Hostetler
2021-09-18  8:59       ` Ævar Arnfjörð Bjarmason
2021-09-16  5:55   ` Ævar Arnfjörð Bjarmason
2021-09-20 15:36 ` [PATCH v2 0/7] Builtin FSMonitor Part 1 Jeff Hostetler via GitGitGadget
2021-09-20 15:36   ` [PATCH v2 1/7] trace2: add trace2_child_ready() to report on background children Jeff Hostetler via GitGitGadget
2021-09-20 15:36   ` [PATCH v2 2/7] simple-ipc: preparations for supporting binary messages Jeff Hostetler via GitGitGadget
2021-09-20 15:36   ` [PATCH v2 3/7] simple-ipc: move definition of ipc_active_state outside of ifdef Jeff Hostetler via GitGitGadget
2021-09-20 15:36   ` [PATCH v2 4/7] simple-ipc/ipc-win32: add trace2 debugging Jeff Hostetler via GitGitGadget
2021-09-20 15:36   ` [PATCH v2 5/7] simple-ipc/ipc-win32: add Windows ACL to named pipe Jeff Hostetler via GitGitGadget
2021-09-20 15:36   ` [PATCH v2 6/7] run-command: create start_bg_command Jeff Hostetler via GitGitGadget
2021-09-20 15:36   ` [PATCH v2 7/7] t/helper/simple-ipc: convert test-simple-ipc to use start_bg_command Jeff Hostetler via GitGitGadget
2021-09-23 15:03     ` Ævar Arnfjörð Bjarmason
2021-09-23 17:58       ` Jeff Hostetler
2021-09-23 18:37       ` Junio C Hamano
2021-11-04 19:46     ` Adam Dinwoodie
2021-11-04 20:14       ` Ramsay Jones
2021-11-08 14:58       ` Jeff Hostetler
2021-11-08 23:59       ` Johannes Schindelin
2021-11-09 18:53         ` Ramsay Jones [this message]
2021-11-09 23:01           ` Johannes Schindelin
2021-11-09 23:34             ` Junio C Hamano
2021-11-10 12:27               ` Johannes Schindelin
2021-11-12  8:56                 ` Adam Dinwoodie
2021-11-12 16:01                   ` Junio C Hamano
2021-11-12 21:33                     ` Adam Dinwoodie
2021-11-16 10:56                       ` Johannes Schindelin
2021-11-16 11:02                   ` Johannes Schindelin
2021-11-13 19:11                 ` Ramsay Jones
2021-11-14 19:34                   ` Ramsay Jones
2021-11-14 20:10                   ` Adam Dinwoodie
2021-09-23 14:33   ` [PATCH v2 0/7] Builtin FSMonitor Part 1 Ævar Arnfjörð Bjarmason
2021-09-23 17:12     ` Jeff Hostetler
2021-09-23 20:47       ` Ævar Arnfjörð Bjarmason
2021-09-27 13:37         ` Jeff Hostetler
2021-09-23 17:51     ` Taylor Blau

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