On 01/06/2014 06:54 PM, Junio C Hamano wrote:
Michael Haggerty mhag...@alum.mit.edu writes:
If safe_create_leading_directories() fails because a file along the
path unexpectedly vanished, try again (up to 3 times).
This can occur if another process is deleting directories at the same
time as we are trying to make them. For example, git pack-refs
--all tries to delete the loose refs and any empty directories that
are left behind. If a pack-refs process is running, then it might
delete a directory that we need to put a new loose reference in.
If safe_create_leading_directories() thinks this might have happened,
then take its advice and try again (maximum three attempts).
Signed-off-by: Michael Haggerty mhag...@alum.mit.edu
---
refs.c | 11 ++-
1 file changed, 10 insertions(+), 1 deletion(-)
diff --git a/refs.c b/refs.c
index 3926136..6eb8a02 100644
--- a/refs.c
+++ b/refs.c
@@ -2039,6 +2039,7 @@ static struct ref_lock *lock_ref_sha1_basic(const char
*refname,
int type, lflags;
int mustexist = (old_sha1 !is_null_sha1(old_sha1));
int missing = 0;
+int attempts = 3;
lock = xcalloc(1, sizeof(struct ref_lock));
lock-lock_fd = -1;
@@ -2093,7 +2094,15 @@ static struct ref_lock *lock_ref_sha1_basic(const
char *refname,
if ((flags REF_NODEREF) (type REF_ISSYMREF))
lock-force_write = 1;
-if (safe_create_leading_directories(ref_file)) {
+ retry:
+switch (safe_create_leading_directories(ref_file)) {
+case SCLD_OK:
+break; /* success */
+case SCLD_VANISHED:
+if (--attempts 0)
+goto retry;
+/* fall through */
Hmph.
Having no backoff/sleep at all might be OK here as long as the other
side that removes does not retry (and I do not think the other side
would, even though I haven't read through the series to the end yet
;-)).
remove_dir_recurse() only tries deleting directories once (I haven't
changed that). And from a broader perspective, it would be pretty silly
for any tidy-up-directories function to try deleting things more than
once. So I don't think it is a problem. But even in the worst case,
this function only tries three times before giving up, so it shouldn't
be a disaster.
This may be just a style thing, but I find that the variable name
attempts that starts out as 3 quite misleading, as its value is
not the number of attempts made but the remaining number of
attempts allowed. Starting it from 0 and then
if (attempts++ MAX_ATTEMPTS)
goto retry;
would be one way to clarify it. Renaming it to remaining_attempts
would be another.
I just renamed the variable to attempts_remaining. (I thought I was
following your suggestion, but now I see that I put the words in the
opposite order; oh well, I think it's fine either way.)
Thanks for your review! I will wait a day or so for any additional
comments, and then send a v3.
Michael
--
Michael Haggerty
mhag...@alum.mit.edu
http://softwareswirl.blogspot.com/
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