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@xxxxxxxxxxxxxx>
---
Documentation/git-check-attr.txt | 5 +++++
Documentation/git-check-ignore.txt | 5 +++++
Documentation/git.txt | 16 +++++++++-------
3 files changed, 19 insertions(+), 7 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 6a875f2..eecdb15 100644
--- a/Documentation/git.txt
+++ b/Documentation/git.txt
@@ -808,13 +808,15 @@ 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
- 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
- based on whether stdout appears to be redirected to a file or not.
+ as 'git blame' (in incremental mode), 'git rev-list', 'git
+ log', 'git check-attr', 'git check-ignore', and 'git
+ whatchanged' will force a flush of the output stream after
+ each commit-oriented 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 based on whether stdout appears to be
+ redirected to a file or not.
'GIT_TRACE'::
If this variable is set to "1", "2" or "true" (comparison
--
1.8.2.1.342.gfa7285d
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