[PATCH 11/12] cpukit/libblock: Workaround SMP problem in bdbuf

[Sebastian Huber]

On 2014-05-27 17:21, Gedare Bloom wrote:
> On Tue, May 27, 2014 at 10:48 AM, Ralf Kirchner
> <ralf.kirchner at embedded-brains.de>  wrote:
>> >Enabling and disabling preemption as done for single core will not work for SMP.
>> >Thus as a temporary workaround use POSIX mutexes and POSIX condition variables for SMP instead of the combination of semaphores and preemption handling used for single core.
>> >---
>> >  cpukit/libblock/src/bdbuf.c |  348 +++++++++++++++++++++++++++++++++++--------
>> >  1 Datei geändert, 282 Zeilen hinzugefügt(+), 66 Zeilen entfernt(-)
>> >
>> >diff --git a/cpukit/libblock/src/bdbuf.c b/cpukit/libblock/src/bdbuf.c
>> >index 1e4887c..0caf8f5 100644
>> >--- a/cpukit/libblock/src/bdbuf.c
>> >+++ b/cpukit/libblock/src/bdbuf.c
>> >@@ -43,6 +43,23 @@
>> >
>> >  #include "rtems/bdbuf.h"
>> >
>> >+#if defined( RTEMS_SMP )
>> >+  #if defined( RTEMS_POSIX_API )
>> >+    /* The single core implementation with enabling and disabling preemption
>> >+     * will not work under SMP. Thus we need to use POSIX mutexes and POSIX
>> >+     * condition variables as a workaround
>> >+     * Required POSIX mutexes and POSIX condition variables will be allocated
>> >+     * automatically in confdefs.h if RTEMS_SMP and RTEMS_POSIX_API
>> >+     * are #defined
>> >+     */
>> >+    #define RTEMS_BDBUF_SMP_WORKAROUND
> Workaround implies a temporary solution. Is there a longer-term
> solution in the works? Otherwise, we should just condition this on
> RTEMS_SMP?

We need condition variables in the Classic API.

>
> What if RTEMS_SMP is defined, but RTEMS_POSIX_API is not? This would
> be an error here I suppose? Or possibly elsewhere in the bdbuf
> workaround code? Probably it should be accounted in confdefs.h and an
> error emitted?
>

RTEMS_SMP without RTEMS_POSIX_API falls back to the current situation.  You get 
a fatal error at run-time.  A compile-time error is bad, since this would break 
the test suite build.

-- 
Sebastian Huber, embedded brains GmbH

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