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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. 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 <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
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@ -697,13 +697,21 @@ test_expect_success PIPE 'streaming support for --stdin' '
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# shell, and then echo to the fd. We make sure to close it at
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# the end, so that the subprocess does get EOF and dies
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# properly.
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#
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# Similarly, we must keep "out" open so that check-ignore does
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# not ever get SIGPIPE trying to write to us. Not only would that
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# produce incorrect results, but then there would be no writer on the
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# other end of the pipe, and we would potentially block forever trying
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# to open it.
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exec 9>in &&
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exec 8<out &&
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test_when_finished "exec 9>&-" &&
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test_when_finished "exec 8<&-" &&
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echo >&9 one &&
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read response <out &&
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read response <&8 &&
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echo "$response" | grep "^\.gitignore:1:one one" &&
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echo >&9 two &&
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read response <out &&
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read response <&8 &&
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echo "$response" | grep "^:: two"
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'
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