forked from Imagelibrary/rtems
146adb1edf
The SPARC ABI is a bit special with respect to the floating point context. The complete floating point context is volatile. Thus, from an ABI point of view nothing needs to be saved and restored during a context switch. Instead the floating point context must be saved and restored during interrupt processing. Historically, the deferred floating point switch was used for SPARC and the complete floating point context is saved and restored during a context switch to the new floating point unit owner. This is a bit dangerous since post-switch actions (e.g. signal handlers) and context switch extensions may silently corrupt the floating point context. The floating point unit is disabled for interrupt handlers. Thus, in case an interrupt handler uses the floating point unit then this will result in a trap (INTERNAL_ERROR_ILLEGAL_USE_OF_FLOATING_POINT_UNIT). In uniprocessor configurations, a lazy floating point context switch is used. In case an active floating point thread is interrupted (PSR[EF] == 1) and a thread dispatch is carried out, then this thread is registered as the floating point owner. When a floating point owner is present during a context switch, the floating point unit is disabled for the heir thread (PSR[EF] == 0). The floating point disabled trap checks that the use of the floating point unit is allowed and saves/restores the floating point context on demand. Update #3077.
This is the Real-Time Executive for Multiprocessing Systems (RTEMS). The version number for this software is indicated in the VERSION file. See the documentation manuals in doc/ with daily builds available online at http://rtems.org/onlinedocs/doc-current/share/rtems/html/ and released builds at http://www.rtems.org/onlinedocs/releases/ for information on building, installing, and using RTEMS. The INSTALL file tells you to come back here. See the RTEMS Wiki at http://devel.rtems.org for community knowledge and tutorials. RTEMS Doxygen available at http://www.rtems.org/onlinedocs/doxygen/cpukit/html The RTEMS Project maintains mailing lists which are used for most discussions: * For general-purpose questions related to using RTEMS, use the rtems-users ml: https://lists.rtems.org/mailman/listinfo/users * For questions and discussion related to development of RTEMS, use the rtems-devel ml: https://lists.rtems.org/mailman/listinfo/devel See https://devel.rtems.org/ to view existing or file a new issue report ticket.