Jeff King <p...@peff.net> writes: > Subject: [PATCH] t0008: avoid SIGPIPE race condition on fifo > > To test check-ignore's --stdin feature, we use two fifos to > send and receive data. We carefully keep a descriptor to its > input open so that it does not receive EOF between input > lines. However, we do not do the same for its output. That > means there is a potential race condition in which > check-ignore has opened the output pipe once (when we read > the first line), and then writes the second line before we > have re-opened the pipe. > > In that case, check-ignore gets a SIGPIPE and dies. The > outer shell then tries to open the output fifo but blocks > indefinitely, because there is no writer. We can fix it by > keeping a descriptor open through the whole procedure.
Ahh, figures. I wish I were smart enough to figure that out immediately after seeing the test that does funny things to "in" with "9". Thanks. > This should also help if check-ignore dies for any other > reason (we would already have opened the fifo and would > therefore not block, but just get EOF on read). > > However, we are technically still susceptible to > check-ignore dying early, before we have opened the fifo. > This is an unlikely race and shouldn't generally happen in > practice, though, so we can hopefully ignore it. > > Signed-off-by: Jeff King <p...@peff.net> > --- > t/t0008-ignores.sh | 12 ++++++++++-- > 1 file changed, 10 insertions(+), 2 deletions(-) > > diff --git a/t/t0008-ignores.sh b/t/t0008-ignores.sh > index a56db80..c29342d 100755 > --- a/t/t0008-ignores.sh > +++ b/t/t0008-ignores.sh > @@ -697,13 +697,21 @@ test_expect_success PIPE 'streaming support for > --stdin' ' > # shell, and then echo to the fd. We make sure to close it at > # the end, so that the subprocess does get EOF and dies > # properly. > + # > + # Similarly, we must keep "out" open so that check-ignore does > + # not ever get SIGPIPE trying to write to us. Not only would that > + # produce incorrect results, but then there would be no writer on the > + # other end of the pipe, and we would potentially block forever trying > + # to open it. > exec 9>in && > + exec 8<out && > test_when_finished "exec 9>&-" && > + test_when_finished "exec 8<&-" && > echo >&9 one && > - read response <out && > + read response <&8 && > echo "$response" | grep "^\.gitignore:1:one one" && > echo >&9 two && > - read response <out && > + read response <&8 && > echo "$response" | grep "^:: two" > ' -- To unsubscribe from this list: send the line "unsubscribe git" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
