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Diffstat (limited to 'camel/README.mt')
| -rw-r--r-- | camel/README.mt | 171 |
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diff --git a/camel/README.mt b/camel/README.mt deleted file mode 100644 index aeece1b0bb..0000000000 --- a/camel/README.mt +++ /dev/null @@ -1,171 +0,0 @@ - -This version of camel is working towards being multi-thread safe -(MT-SAFE). At least, for the important api's. - -This code has now been merged into the main head, but this file -will remain here as a log of how it was done, incase any issues -arise. The ChangeLog of course has a much more detailed list -of changes. - -Intended method -=============== - -I intend working on it in several stages: - -1. Making the api multi-threadable. Basically removing some const-returns, -and copying some data where it wasn't before. The api should -still continue to work if not being used in a multithreaded -application. There is not a significant amount of work here since -this was more or less the intention all along. - -Some functions where references to objects are returned may have to be -changed slightly, so that refcounts are incremented before return. -This doesn't affect much though. - -camel_folder::get_message_info done -camel_folder_summary::uid done -camel_folder_summary::index done -camel_folder::get_summary - Needs to ref each summary item it points to. done -camel_folder::free_summary - Needs to unref each summary item it points to. done -camel_folder_get_message_tag - needs to copy the tag return -camel_maildir_summary filename string - should not be able to modify the string - array contents after it has been added to - the summary. -camel_folder done - Make every camel-folder use a camel-folder-summary. - This just reduces some of the code duplication, - since everything but vee-folder does this already. - -2. Adding high level locks for proof of concept. The locks will -be stored in private or global data, so the api should remain the same for -non-threaded applications. - -A per-folder lock which governs access to the folder - summary, the folder file or - communications socket, etc. done -Locking for exceptions. done -Per store locks for internal stuff. done -Per-service locks for various internal lists and - caches done - -3. Further fine-grained locking where it can be done/is worthwhile. - -A per-index lock for libibex done -Locking for the search object half done -Internal lock for the folder_summary itself - So that searching can be detatched from other - folder operations, etc. done -Possibly a lock for access to parts of a mime-part - or message - -4. A method to cancel operations. - -Individual outstanding operations must be cancellable, and not just -'all current operations'. This will probably not use pthread_cancel -type of cancelling. - -This will however, probably use a method for starting a new thread, -through camel, that can then be cancelled, and/or some method of -registering that a thread can be cancelled. Blocking states within -camel, within that thread, will then act as checkpoints for if the -operation, and if it is cancelled, the operation will abort -(i.e. fail, with an appropriate exception code). - -Operation cancelling should also function when the application is not -multi-threaded. Not sure of the api for this yet, probably a callback -system. Hopefully the api for both scenarios can be made the same. - -Other thoughts -============== - -Basically much of the code in camel that does the actual work does NOT -need to be thread safe to make it safely usable in an mt context. - -camel-folder, camel-summary, camel-imap-search, and the camel-service -classes (at least) are the important ones to be made multithreaded. - -For other things, they are either resources that are created -one-off (for example, camel-mime-message, and its associated -parts, like camel-internet-address), or multithreadedness -doesn't make a lot of sense - e.g. camel-stream, or camel-mime-parser. - -So basically the approach is a low-risk one. Adding the minimum -number of locks to start with, and providing further fine-grained -locks as required. The locks should not need to be particularly -fine-grained in order to get reasonable results. - -Log of changes -============== - -Changed CamelFolder:get_message_info() to return a ref'd copy, requiring -all get_message_info()'s to have a matching free_message_info(). - -Moved the CamelFolder frozen changelog data to a private structure. - -Added a mutex for CamelFolder frozen changelog stuff (it was just easy -to do, although it isn't needed yet). - -Added a single mutex around all other CamelFolder functions that need -it, this is just the first cut at mt'edness. - -Fixed all camel-folder implementations that call any other -camel-folder functions to call via virtual methods, to bypass the locks. - -Added camel-store private data. - -Added a single mutex lock for camel-store's folder functions. - -Added camel-service private data. - -Added a single mutex lock for camel-service's connect stuff. - -Added a mutex for remote-store stream io stuff. - -Added a mutex for imap, so it can bracket a compound command -exclusively. Pop doesn't need this since you can only have a single -folder per store, and the folder interface is already forced -single-threaded. - -Added mutex for camel-session, most operations. - -Running the tests finds at least 1 deadlock so far. Need to -work on that. - -Fixed get_summary to ref/unref its items. - -Removed the global folder lock from the toplevel -camel_folder_search(), each implementation must now handle locking. - -Fixed the local-folder implementation of searching. imap-folder -searching should already be mt-safe through the command lock. - -Fixed imap summary to ref/unref too. - -Built some test cases, and expanded the test framework library to -handle multiple threads. It works! - -Next, added a recursive mutex class, so that locking inside imap had -any chance of working. Got imap working. - -Moved the camel folder summary into the base folder class, and fixed -everything to use it that way. - -Made the vfolder use a real camel-folder-summary rather than a -hashtable + array that it was using, and probably fixed some problems -which caused evolution-mail not to always catch flag updates. Oh, and -made it sync/expunge all its subfolders when sync/expungeing. - -Made the camel-folder summary completely mt-safe. - -Removed all of the locks on the folder functions dealing directly with -the summary, so now for example all summary lookups will not be -interupted by long operations. - -Made the nntp newsrc thing mt-safe, because of some unfortunate -sideeffect of it being called from the summary interaction code in -nntp-folder. - |