RE: [patch] sched: unlocked context-switches

[Luck, Tony]

>tested on x86, and all other arches should work as well, but if an 
>architecture has irqs-off assumptions in its switch_to() logic 
>it might break. (I havent found any but there may such assumptions.)

The ia64_switch_to() code includes a section that can change a pinned
MMU mapping (when the stack for the new process is in a different
granule from the stack for the old process).  The code beyond the ".map"
label in arch/ia64/kernel/entry.S includes the comment:

.map:
        rsm psr.ic                      // interrupts (psr.i) are already disabled here

I don't think that it would be sufficient to merely add psr.i to this rsm
(and to the ssm 15 lines above).  That would leave a window where we could
take an interrupt, but not be sure that the current stack is pinned.

-Tony
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/