Understanding stop_machine() use for cpu_down()

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



Hi,

I'm trying to understand why stop_machine() is necessary for
cpu_down() operation.

I see that multi_cpu_stop() on every online cpu (which hogs the cpu
and then triggers state changes state)
and then, take_cpu_down is invoked on the outgoing cpu.
This happens by every cpu decrementing the msdata->thread_ack and last
one trigger a state change.

I'm trying to understand why is this necessary.

Is to wait for RCU grace period(s)?
If yes, what variable/struct is being protected and how does
stop_machine() help there?

I see there was a patch (https://lwn.net/Articles/538819/) but had
some issues with idle_loop.

Is there an alternative where the stop_machine would not be necessary?
Or more specifically, is there a reason why every CPU would need to stop?

Any help would be appreciated.

Thanks,
Hardik
--
To unsubscribe from this list: send the line "unsubscribe linux-hotplug" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html



[Index of Archives]     [Linux Kernel]     [Linux DVB]     [Asterisk Internet PBX]     [DCCP]     [Netdev]     [X.org]     [Util Linux NG]     [Fedora Women]     [ALSA Devel]     [Linux USB]

  Powered by Linux