Some problems with the libbsd update

[Sebastian Huber]

On 22/08/18 13:44, Joel Sherrill wrote:
>
>
> On Wed, Aug 22, 2018, 4:51 AM Sebastian Huber 
> <sebastian.huber at embedded-brains.de 
> <mailto:sebastian.huber at embedded-brains.de>> wrote:
>
>     On 22/08/18 09:50, Sebastian Huber wrote:
>     > To support everything in RTEMS is a lot of work, so I have to make
>     > some trade-offs. The implementation of this API must be as
>     efficient
>     > as possible since it is used in the critical paths of the network
>     > stack. I will try to use a single global epoch and thread-specific
>     > records as suggested by Matthew Macy to avoid the need for
>     > per-processor data structures and the thread pinning. One key
>     issue is
>     > that epoch records must not be destroyed:
>     >
>     > https://www.mankier.com/3/ck_epoch_register
>     >
>     > The consequence of this is that unlimited thread objects may
>     lead to
>     > undefined behaviour with this implementation approach. Also
>     > thread-local storage cannot be used since it is reinitialized
>     once a
>     > thread restarted or reused. The epoch record must be included in
>     the
>     > Thread_Control and must not be touched by _Thread_Initialize().
>     This
>     > means I have to move the API and its implementation along with the
>     > Concurrency Kit to RTEMS.
>
>     Ok, there is also an
>
>     http://www.concurrencykit.org/doc/ck_epoch_unregister.html
>
>     and
>
>     http://www.concurrencykit.org/doc/ck_epoch_recycle.html
>
>     This allows a localized implementation in libbsd.
>
>     Due to performance reasons this requires the use of thread-local
>     storage. Any objections to make thread-local storage a hard
>     requirement
>     for libbsd support?
>
>
> Not particularly but there should be an effort to identify which 
> targets do not have TLS support yet. Other than sparc, arm, powerpc 
> and i386, I don't know the status. Sounds like a series of tickets.

TLS is also supported on m68k and riscv. Are the other targets 
maintained at all?

-- 
Sebastian Huber, embedded brains GmbH

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