Re: [PATCH v5 07/35] hold_lock_file_for_append(): release lock on errors

2014-09-17 Thread Michael Haggerty
On 09/16/2014 10:48 PM, Jonathan Nieder wrote:
 Michael Haggerty wrote:
 
 --- a/lockfile.c
 +++ b/lockfile.c
 @@ -219,13 +219,13 @@ int hold_lock_file_for_append(struct lock_file *lk, 
 const char *path, int flags)
  if (errno != ENOENT) {
  if (flags  LOCK_DIE_ON_ERROR)
  die(cannot open '%s' for copying, path);
 -close(fd);
 +rollback_lock_file(lk);
  return error(cannot open '%s' for copying, path);
 
 Makes sense.
 
 Now that I'm here, I wonder a little at the error convention.  If the
 caller doesn't pass LOCK_DIE_ON_ERROR, are they supposed to be able to
 use unable_to_lock_message?  What errno would they pass in the err
 parameter?  Would callers want handle failure to acquire a lock
 differently from other errors (e.g., by sleeping and trying again),
 and if not, what is the optionally-die behavior in hold_lock_file
 about?

The same applies to hold_lock_file_for_update(), so I'll discuss both at
once:

Most callers do pass LOCK_DIE_ON_ERROR. Of the ones that don't, a couple
appear to want to emit more meaningful error messages. A couple don't
die at all but return an error code to their caller. At least one
(add_to_alternates_file()) calls die_errno().

As it happens, hold_lock_file_for_append() sometimes overwrites errno
before it returns. I will add a patch on top of this series that fixes that.

I don't see any callers that retry, though I've thought about
implementing that in some places. But it's outside of the scope of this
patch series.

Michael

-- 
Michael Haggerty
mhag...@alum.mit.edu

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Re: [PATCH v5 07/35] hold_lock_file_for_append(): release lock on errors

2014-09-16 Thread Jonathan Nieder
Michael Haggerty wrote:

 --- a/lockfile.c
 +++ b/lockfile.c
 @@ -219,13 +219,13 @@ int hold_lock_file_for_append(struct lock_file *lk, 
 const char *path, int flags)
   if (errno != ENOENT) {
   if (flags  LOCK_DIE_ON_ERROR)
   die(cannot open '%s' for copying, path);
 - close(fd);
 + rollback_lock_file(lk);
   return error(cannot open '%s' for copying, path);

Makes sense.

Now that I'm here, I wonder a little at the error convention.  If the
caller doesn't pass LOCK_DIE_ON_ERROR, are they supposed to be able to
use unable_to_lock_message?  What errno would they pass in the err
parameter?  Would callers want handle failure to acquire a lock
differently from other errors (e.g., by sleeping and trying again),
and if not, what is the optionally-die behavior in hold_lock_file
about?

In any case,
Reviewed-by: Jonathan Nieder jrnie...@gmail.com
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