Ciao Thomas,

this new version of the preempt-rt patch seems to be a good step forward with respect to a problem I have in a benchmark application I am running on top of a kernel v2.6.29.4 patched with it on a quad-core Intel(R) Xeon(R) machine. Within this benchmark I am making use of pthreads and semaphores and sometime it happens that a call to "sem_wait()" returns "-1" and sets the "errno" to "512" - which corresponds to "ERESTARTSYS" - which up to my poor kernel knowledge should never be delivered to the user space. Now, with the new version of the preempt-rt patch, the frequency of these odd "sem_wait()" return values has notably diminished, though not completely stopped. So, I thought it might be interesting for you if I share a workaround with you which seems to eliminate the odd "sem_wait()" return values (as it did work already for preempt-rt patch version rt17). Note, that this for sure is not a bug fix, but just a workaround for which I am even not a 100% sure that it is semantically correct, but maybe it gives you a hint on what might still go wrong in the RT patch. Pls. find attach the "rcsdiff" output on file "kernel/futex.c" containing the workaround.

Best regards, Wolfgang Betz

=================================================================== RCS file: kernel/RCS/futex.c,v retrieving revision 1.1 diff -r1.1 kernel/futex.c

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