On 11/8/18 2:15 PM, Jan Kiszka wrote: > On 08.11.18 14:09, Philippe Gerum wrote: >> On 11/8/18 2:05 PM, Philippe Gerum via Xenomai wrote: >>> On 11/5/18 1:20 PM, Jan Kiszka wrote: >>>> 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. >>> >>> ARM-wise, this change requires ipipe-core-4.14.71-arm-3 or later to work >>> properly. This method would cause an interrupt state breakage with any >>> older ARM patch. >>> >> >> ppc32 is fine back to kernel 4.1 regarding this (did not check earlier >> stuff), and arm64 needs the 4.14-based split series to work properly >> (4.9 is wrong). > > Is the reason for arm64 on 4.9 the same as for arm? >
Yes, same pattern. -- Philippe.
