RE: [ANNOUNCE] Git v2.32.0-rc3 - t5300 Still Broken on NonStop ia64/x86

On June 2, 2021 4:14 PM, Peff wrote:

Subject: Re: [ANNOUNCE] Git v2.32.0-rc3 - t5300 Still Broken on NonStop ia64/x86
On Wed, Jun 02, 2021 at 08:11:50PM +0000, Eric Wong wrote:

quoted

Jeff King [off-list ref] wrote:

quoted

And so when he gets this error:

  fatal: fsync error on '.git/objects/pack/tmp_pack_NkPgqN':
Interrupted system call

presumably we were in fsync() when the signal arrived, and unlike
most other platforms, the call needs to be restarted manually (even
though we set up the signal with SA_RESTART). I'm not sure if this
violates POSIX or not (I couldn't find a definitive answer to the
set of interruptible functions in the standard). But either way, the
workaround is probably something like:

"man 3posix fsync" says EINTR is allowed ("manpages-posix-dev"
package in Debian non-free).

Ah, thanks. Linux's fsync(3) doesn't mention it, and nor does it appear in the discussion of interruptible calls in signals(7). So I was looking
for a POSIX equivalent of that signals manpage but couldn't find one. :)

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  #ifdef FSYNC_NEEDS_RESTART

The wrapper should apply to all platforms.  NFS (and presumably other
network FSes) can be mounted with interrupts enabled.

I don't mind that, as the wrapper is pretty low-cost (and one less Makefile knob is nice). If it's widespread, though, I find it curious that
nobody has run into it before now.

I suspect this is because of the way the file system on NonStop behaves. It is a multi-processor platform, with multi-cores, so anything can happen. If the file system is delayed for any reason, like a signal coming from a different core (EINTR has high priority), then fsync() will be interrupted. EINTR is allowed on NonStop for fsync(). So it would be really great if the patch included a modification to config.mak.uname to include that. This would be a timing-only issue on most other systems, probably something that would hit NFS.

The patch for the config is:

diff --git a/config.mak.uname b/config.mak.uname
index cb443b4e02..ac3e3ca2c5 100644
--- a/config.mak.uname
+++ b/config.mak.uname

@@ -566,6 +566,7 @@ ifeq ($(uname_S),NONSTOP_KERNEL)
        NO_REGEX = NeedsStartEnd
        NO_PTHREADS = UnfortunatelyYes
        FREAD_READS_DIRECTORIES = UnfortunatelyYes
+       FSYNC_NEEDS_RESTART = YesPlease

        # Not detected (nor checked for) by './configure'.