Brian Havard wrote:
On 08/10/10 23:21, Stefan Ruppert wrote:
I have filed a bug in bugzilla for this issue:
https://issues.apache.org/bugzilla/show_bug.cgi?id=50058
and added a patch which simple removes the calls to apr_file_lock()
and apr_file_unlock()!
Please can some test this!?
As I remember it, the file lock is used to ensure proper appending
behaviour. This is necessary because windows doesn't natively have an
append mode so it's necessary to seek to the end of the file then write.
The file lock is used to prevent a race condition when multiple
threads/processes are writing to the same file simultaneously.
The deadlock problem needs to be solved by suppressing locking for
append if a lock is already held, not by simply removing the locking
completely.
I don't agree. IMHO, a framework (like APR) shouldn't be too clever. The
application has to decide if it uses a file which can be accessed from
different threads or processes and needs locking. Regarding threading
see the ML-thread "apr_file_*() threading issues under Windows" for
using apr_file_*() API through threads.
Regarding locking a file, I would like to see that the calls to
apr_file_lock()/apr_file_unlock() are removed from the apr_file_write()
call. From my usage scenario I need to lock the file over several calls
to apr_file_write() and why add more complexity if the application needs
locking by itself!? Also currently with such locking the semantic of the
apr_file_write() differs between Windows and Unix like OSs.
Also I would like to see a APR_FOPEN_LOCK which locks the file within
apr_file_open() call and unlocks the file within apr_file_close() call.
Stefan Ruppert wrote:
Hi all,
yesterday I ran into the following problem. I use the apr_file_lock()
function in conjunction with the APR_FOPEN_APPEND flag and under
Linux everything is fine.
Under Windows any attempt to write to the opened and locked file I
get a deadlock. This is due the fact that apr_file_write() creates an
own lock with apr_file_lock() if the file was opened with the
APR_FOPEN_APPEND flag.
First this is inconsistent through different operating systems Unix
does not lock, Windows does lock the file in append mode. However, I
think the locking in the Windows implementation is wrong. The user
has to choose if he wants to lock the file or not!
To reproduce the behavior please compile and test the attached example!
Any comments? Should I file a bug report?
Regards,
Stefan
