On 15 July 2013 15:35, Srivatsa S. Bhat <srivatsa.b...@linux.vnet.ibm.com> wrote: > Actually even I was wondering about this while writing the patch and > I even tested shutdown after multiple suspend/resume cycles, to verify that > the refcount is messed up. But surprisingly, things worked just fine. > > Logically there should've been a refcount mismatch and things should have > failed, but everything worked fine during my tests. Apart from suspend/resume > and shutdown tests, I even tried mixing a few regular CPU hotplug operations > (echo 0/1 to sysfs online files), but nothing stood out. > > Sorry, I forgot to document this in the patch. Either the patch is wrong > or something else is silently fixing this up. Not sure what is the exact > situation.
To understand it I actually applied your patches to get better view of the code. (Haven't tested it though).. And found that your code is doing the right thing and we shouldn't get a mismatch.. This is the sequence of events I can draw: - __cpu_add_dev() for first cpu. sets the refcount to 'x', where x are the no. of cpus in its clock domain. - _cpu_add_dev() for other cpus: doesn't change anything in refcount - Suspend: - cpu_remove_dev() for all cpus, due to frozen flag we don't touch the value of count - Resume: - cpu_add_dev() for all cpus, due to frozen flag we don't touch the value of count. And so things work as expected. That's why your code isn't breaking anything I believe. But can no. of cpus change inbetween suspend/resume? Then count would be tricky as we are using the same policy structure. -- 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/
