introduce usage of thread local storage structure

[frankeh]

Reworked the gettid patch as discussed #42.

[MadCoder]

should be on the same line

[MadCoder]

Additional comments:
I think you're missing patches, at least in init.c. Look for DISPATCH_USE_DIRECT_TSD in the source, it's likely that you will want to also have DISPATCH_USE_THREAD_LOCAL_STORAGE clauses around them too. e.g. in init.c you have (may be slightly different

#if !DISPATCH_USE_DIRECT_TSD
pthread_key_t dispatch_queue_key;
pthread_key_t dispatch_sema4_key;
...

that should definitely become:

-#if !DISPATCH_USE_DIRECT_TSD
+#if !DISPATCH_USE_DIRECT_TSD && ! DISPATCH_USE_THREAD_LOCAL_STORAGE
pthread_key_t dispatch_queue_key;
pthread_key_t dispatch_sema4_key;
...

Or this:

#if DISPATCH_USE_DIRECT_TSD
const struct dispatch_tsd_indexes_s dispatch_tsd_indexes = {
    .dti_version = 2,
    .dti_queue_index = dispatch_queue_key,
    .dti_voucher_index = dispatch_voucher_key,
    .dti_qos_class_index = dispatch_priority_key,
};
#else // DISPATCH_USE_DIRECT_TSD
#ifndef __LINUX_PORT_HDD__
#error Not implemented on this platform
#endif
#endif // DISPATCH_USE_DIRECT_TSD

looks wrong, I think it's fine for a platform to not have some bits of the introspection that make no sense for the platform. Here I would just remove the #error for everyone (though @das may disagree?).

Overall this is going in the right direction, and I think it will be a tremendous performance improvement on linux.

Also, @das will need to review that one too, he'll probably have comments on top of mine

[frankeh]

@das Is there anything else you would like addressed or you have concerns with
or can we merge

[das]

sorry have not yet had time to look

[MadCoder]

replaced with #82