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Jan Kiszka authored
The mayday mechanism exists in order to kick a xenomai userspace task into secondary mode while it is running userspace code. For that, we ask I-pipe to call us back when the task was interrupted and is about to return to userspace. So far we defer the relaxation from that callback via a VDSO-like mechanism that triggers a special syscall to the return path of that very same syscall. However, that is not desirable because it is a complex, arch-specific mechanism that can easily break and, specifically, that destroys the backtrace of ptraced tasks. Fortunately, we can fulfill the needs of mayday also by relaxing the task directly from the mayday callback. Tested successfully on x86-64 and ARM. Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
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