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| author | Adam Spiers <git@adamspiers.org> | 2013-04-11 12:05:13 (GMT) |
|---|---|---|
| committer | Junio C Hamano <gitster@pobox.com> | 2013-04-11 18:11:36 (GMT) |
| commit | f1ed7fea7974218db15155f3b8d2e29d3fe0971c (patch) | |
| tree | 6e84f63ddd4fb3a927d2ef2cc2829c0d566ac7b8 | |
| parent | 0c8e8c080b08632d6dbee33d093b5df648196b49 (diff) | |
| download | git-f1ed7fea7974218db15155f3b8d2e29d3fe0971c.zip git-f1ed7fea7974218db15155f3b8d2e29d3fe0971c.tar.gz git-f1ed7fea7974218db15155f3b8d2e29d3fe0971c.tar.bz2 | |
Documentation: add caveats about I/O buffering for check-{attr,ignore}
check-attr and check-ignore have the potential to deadlock callers
which do not read back the output in real-time. For example, if a
caller writes N paths out and then reads N lines back in, it risks
becoming blocked on write() to check-*, and check-* is blocked on
write back to the caller. Somebody has to buffer; the pipe buffers
provide some leeway, but they are limited.
Thanks to Peff for pointing this out:
http://article.gmane.org/gmane.comp.version-control.git/220534
Signed-off-by: Adam Spiers <git@adamspiers.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
| -rw-r--r-- | Documentation/git-check-attr.txt | 5 | ||||
| -rw-r--r-- | Documentation/git-check-ignore.txt | 5 | ||||
| -rw-r--r-- | Documentation/git.txt | 5 |
3 files changed, 13 insertions, 2 deletions
diff --git a/Documentation/git-check-attr.txt b/Documentation/git-check-attr.txt index 5abdbaa..a7be80d 100644 --- a/Documentation/git-check-attr.txt +++ b/Documentation/git-check-attr.txt @@ -56,6 +56,11 @@ being queried and <info> can be either: 'set';; when the attribute is defined as true. <value>;; when a value has been assigned to the attribute. +Buffering happens as documented under the `GIT_FLUSH` option in +linkgit:git[1]. The caller is responsible for avoiding deadlocks +caused by overfilling an input buffer or reading from an empty output +buffer. + EXAMPLES -------- diff --git a/Documentation/git-check-ignore.txt b/Documentation/git-check-ignore.txt index 7e3cabc..8e1f7ab 100644 --- a/Documentation/git-check-ignore.txt +++ b/Documentation/git-check-ignore.txt @@ -81,6 +81,11 @@ not. (Without this option, it would be impossible to tell whether the absence of output for a given file meant that it didn't match any pattern, or that the output hadn't been generated yet.) +Buffering happens as documented under the `GIT_FLUSH` option in +linkgit:git[1]. The caller is responsible for avoiding deadlocks +caused by overfilling an input buffer or reading from an empty output +buffer. + EXIT STATUS ----------- diff --git a/Documentation/git.txt b/Documentation/git.txt index 65c37c4..122b33f 100644 --- a/Documentation/git.txt +++ b/Documentation/git.txt @@ -771,8 +771,9 @@ for further details. 'GIT_FLUSH':: If this environment variable is set to "1", then commands such as 'git blame' (in incremental mode), 'git rev-list', 'git log', - and 'git whatchanged' will force a flush of the output stream - after each commit-oriented record have been flushed. If this + 'git check-attr', 'git check-ignore', and 'git whatchanged' will + force a flush of the output stream after each record have been + flushed. If this variable is set to "0", the output of these commands will be done using completely buffered I/O. If this environment variable is not set, git will choose buffered or record-oriented flushing |