Hi Peff, On Fri, 8 Feb 2019, Johannes Schindelin wrote:
> I just had a look at the patch you provided below (for some reason, my > previous search on public-inbox only turned up Gábor's mail to which you > responded). > > Admittedly, I do not really understand all aspects of it, but it applies, > still, and I kicked off a stress test here: > > https://dev.azure.com/git/git/_build/results?buildId=338 > > It seems that your patch fixes that t5570 flakiness on macOS, and more > importantly, addresses an important issue on macOS. > > Will play a bit more with it and keep you posted. Alas, I was fooled. *Fooled*, I say. Apparently the --stress option makes the script *succeed* when it fails? I say that because I wanted to make sure that your patch fixes things and reverted your change and started another build, which succeeded. So I started another build, then another build, and they all succeeded. Only then it dawned on me that I had not looked at the *logs*. And they all still report the same issue, even with your patch: https://dev.azure.com/git/git/_build/results?buildId=338&view=logs&jobId=51041795-01c5-57f3-5561-107b6b9e51a6&taskId=fadc714a-a906-5cf2-cc7a-335e443ad2f8&lineStart=1402&lineEnd=1505&colStart=1&colEnd=32 (You will have to scroll all the way down, or press Ctrl+End, to see that "fetch notices corrupt pack" is failing.) So I am afraid that your patch does not fix the issue nor does it work around it. Ciao, Dscho > On Tue, 14 Aug 2018, Jeff King wrote: > > > On Mon, Aug 06, 2018 at 05:11:13PM +0200, SZEDER Gábor wrote: > > > > > - 'git upload-pack' receives the request, parses the want line, > > > notices the corrupt pack, responds with an 'ERR upload-pack: not > > > our ref' pkt-line, and die()s right away. > > > > > > - 'git fetch' finally approaches the end of the function, where it > > > attempts to send a done pkt-line via another send_request() call > > > through the now closing TCP socket. > > > > > > - What happens now seems to depend on the platform: > > > > > > - On Linux, both on my machine and on Travis CI, it shows textbook > > > example behaviour: write() returns with error and sets errno to > > > ECONNRESET. Since it happens in write_or_die(), 'git fetch' > > > die()s with 'fatal: write error: Connection reset by peer', and > > > doesn't show the error send by 'git upload-pack'; how could it, > > > it doesn't even get as far to receive upload-pack's ERR > > > pkt-line. > > > > > > The test only checks that 'git fetch' fails, but it doesn't > > > check whether it failed with the right error message, so the > > > test still succeeds. Had it checked the error message as well, > > > we most likely had noticed this issue already, it doesn't happen > > > all that rarely. > > > > Hmm. Traditionally we did not send ERR as part of upload-pack at all. It > > was the message you got from git-daemon if it couldn't start the > > requested sub-process. It was only later in bdb31eada7 (upload-pack: > > report "not our ref" to client, 2017-02-23) that we started sending > > them. So I think that is why it does not check the error message: it is > > not expecting that case at all (and it is not actually interesting here, > > as the real problem is that the remote side is corrupt, but it sadly > > does not say anything so useful). > > > > I think that's somewhat tangential, though. The root of the issue is > > this: > > > > > - On the new OSX images with XCode 9.4 on Travis CI the write() > > > triggers SIGPIPE right away, and 'test_must_fail' notices it and > > > fails the test. I couldn't see any sign of an ECONNRESET or any > > > other error that we could act upon to avoid the SIGPIPE. > > > > Right, as soon as we get SIGPIPE we can't offer any useful message, > > because we're dead. I would argue that fetch should simply turn off > > SIGPIPE entirely, and rely on getting EPIPE from write(). But since > > we're in write_or_die(), it actually turns EPIPE back into a SIGPIPE > > death! > > > > So we'd probably also want to teach it to use a real write_in_full(), > > and then output a more useful message in this case. write_or_die() > > really does produce bad messages regardless, because it doesn't know > > what it's writing to. > > > > That would give us a baby step in the right direction, because at least > > we'd always be doing a controlled die() then. And then the next step > > would be to show the remote error message (even though it's not actually > > useful in this case, in theory upload-pack could generate something > > better). And that would mean turning the die() on write into an attempt > > to drain any ERR messages before either dying or returning an error up > > the stack. > > > > I suspect the (largely untested) patch below would make your test > > problems go away. Or instead, we could simply add sigpipe=ok to the > > test_must_fail invocation, but I agree with you that the current > > behavior on OS X is not ideal (the user sees no error message). > > > > -Peff > > > > diff --git a/fetch-pack.c b/fetch-pack.c > > index 5714bcbddd..3e80604562 100644 > > --- a/fetch-pack.c > > +++ b/fetch-pack.c > > @@ -188,8 +188,10 @@ static void send_request(struct fetch_pack_args *args, > > if (args->stateless_rpc) { > > send_sideband(fd, -1, buf->buf, buf->len, LARGE_PACKET_MAX); > > packet_flush(fd); > > - } else > > - write_or_die(fd, buf->buf, buf->len); > > + } else { > > + if (write_in_full(fd, buf->buf, buf->len) < 0) > > + die_errno("unable to write to remote"); > > + } > > } > > > > static void insert_one_alternate_object(struct fetch_negotiator > > *negotiator, > > @@ -1167,7 +1169,8 @@ static int send_fetch_request(struct fetch_negotiator > > *negotiator, int fd_out, > > > > /* Send request */ > > packet_buf_flush(&req_buf); > > - write_or_die(fd_out, req_buf.buf, req_buf.len); > > + if (write_in_full(fd_out, req_buf.buf, req_buf.len) < 0) > > + die_errno("unable to write request to remote"); > > > > strbuf_release(&req_buf); > > return ret; > > diff --git a/pkt-line.c b/pkt-line.c > > index a593c08aad..450d0801b1 100644 > > --- a/pkt-line.c > > +++ b/pkt-line.c > > @@ -88,13 +88,15 @@ static void packet_trace(const char *buf, unsigned int > > len, int write) > > void packet_flush(int fd) > > { > > packet_trace("0000", 4, 1); > > - write_or_die(fd, "0000", 4); > > + if (write_in_full(fd, "0000", 4) < 0) > > + die_errno("unable to write flush packet"); > > } > > > > void packet_delim(int fd) > > { > > packet_trace("0001", 4, 1); > > - write_or_die(fd, "0001", 4); > > + if (write_in_full(fd, "0000", 4) < 0) > > + die_errno("unable to write delim packet"); > > } > > > > int packet_flush_gently(int fd) > > > >
