The list of threads blocked on an MVar is now represented as a list of separately allocated objects rather than being linked through the TSOs themselves. This lets us remove a TSO from the list in O(1) time rather than O(n) time, by marking the list object. Removing this linear component fixes some pathalogical performance cases where many threads were blocked on an MVar and became unreachable simultaneously (nofib/smp/threads007), or when sending an asynchronous exception to a TSO in a long list of thread blocked on an MVar. MVar performance has actually improved by a few percent as a result of this change, slightly to my surprise. This is the final cleanup in the sequence, which let me remove the old way of waking up threads (unblockOne(), MSG_WAKEUP) in favour of the new way (tryWakeupThread and MSG_TRY_WAKEUP, which is idempotent). It is now the case that only the Capability that owns a TSO may modify its state (well, almost), and this simplifies various things. More of the RTS is based on message-passing between Capabilities now.
Fixes compilation with gcc 4.4
The first phase of this tidyup is focussed on the header files, and in particular making sure we are exposinng publicly exactly what we need to, and no more. - Rts.h now includes everything that the RTS exposes publicly, rather than a random subset of it. - Most of the public header files have moved into subdirectories, and many of them have been renamed. But clients should not need to include any of the other headers directly, just #include the main public headers: Rts.h, HsFFI.h, RtsAPI.h. - All the headers needed for via-C compilation have moved into the stg subdirectory, which is self-contained. Most of the headers for the rest of the RTS APIs have moved into the rts subdirectory. - I left MachDeps.h where it is, because it is so widely used in Haskell code. - I left a deprecated stub for RtsFlags.h in place. The flag structures are now exposed by Rts.h. - Various internal APIs are no longer exposed by public header files. - Various bits of dead code and declarations have been removed - More gcc warnings are turned on, and the RTS code is more warning-clean. - More source files #include "PosixSource.h", and hence only use standard POSIX (1003.1c-1995) interfaces. There is a lot more tidying up still to do, this is just the first pass. I also intend to standardise the names for external RTS APIs (e.g use the rts_ prefix consistently), and declare the internal APIs as hidden for shared libraries.
gcc 4.3 emits warnings for static inline functions that its heuristics decided not to inline. The workaround is to either mark appropriate functions as "hot" (a new attribute in gcc 4.3), or sometimes to use "extern inline" instead. With this fix I can validate with gcc 4.3 on Fedora 9.