![]() | ||||||||||
Messages in this thread |
* Rusty Russell <rusty@rustcorp.com.au> wrote: > D: When CPUs are going down, there is a time when cpu_online(cpu) is > D: false, but they are still scheduling and responding to interrupts > D: (we are migrating things off the CPU, shutting down per-cpu > D: threads, etc). It turns out that RCU cares about these CPUs, so > D: the decision was made to expose this mask (previously internal to x86, > D: and only used for IPIs). these kinds of problems could be avoided by making the CPU-off as much of an atomic operation as possible. The less atomic it is, the more kernel code is exposed to the transitional state - and since this is a rare situation it will always have quality problems. Is there any killer argument that makes it impossible to down a CPU atomically? Kernel threads can get their callbacks on other CPUs just fine. Other tasks should not care. If the migrate-off operation is done 100% atomically then zero knowledge is needed by unrelated scheduler code about the act of disabling a CPU. Ingo - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ | |||||||||
| Last update: 2005-03-22 13:00 [from the cache] ©2003-2008 | ||||||||||