
Linux 5.5 - jrepinc
https://lore.kernel.org/lkml/CAHk-=wigRZ6TSJU09bMk3Df2DiOw83B7TrQUq+iXroQCK5EVAQ@mail.gmail.com/T/
======
jrepinc
New in Linux 5.5:
[https://kernelnewbies.org/Linux_5.5](https://kernelnewbies.org/Linux_5.5)

------
burfog
Of interest is iopl() becoming emulated and losing the ability to grant user
code the ability to disable interrupts. I wonder what user code might have
broken.

The trouble with interrupts being disabled was that it wasn't too well defined
for situations with system calls and exceptions.

I feel like the interrupt functionality could have been usefully emulated. For
example, it could have acted to prevent execution of all tasks which could be
subjected to ptrace by the task that is disabling interrupts. In case the
iopl() caller is root on a system without weird SELinux stuff, the emulation
of turning off interrupts would stop all the other tasks.

Another emulation approach would be to change the scheduling. To emulate the
situation with interrupts off, treat the task as SCHED_FIFO with the highest
priority available to the task.

