Hello, Peter. On Fri, May 16, 2014 at 01:57:37PM +0200, Peter Zijlstra wrote: > This of course leaves the question how the workqueue code manages to > call set_cpu_allowed_ptr() on a cpu _before_ its online. > > That too sounds fishy.. with the proposed patch the > set_cpus_allowed_ptr() will 'gracefully' fail, but calling it in the > first place is of course dubious too.
Right after being created, a workqueue worker invokes set_cpus_allowed_ptr() to the target cpumask without checking whether the cpu[s] are online or not and it's allowed to fail. The guarantee there is that the worker is already registered by that point and if a CPU comes online after the registration, CPU_ONLINE notification will update the cpumask accordingly, so either way the worker is guaranteed to be on the right cpumask. Thanks. -- tejun -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
