On Mon, Jan 08, 2007 at 09:26:56PM -0800, Andrew Morton wrote: > That's not correct. freeze_processes() will freeze *all* processes.
I am not arguing whether all processes will be frozen. However my question was on the freeze point. Let me ask the question with an example: rtasd thread (arch/powerpc/platforms/pseries/rtasd.c) executes this simple loop: static int rtasd(void *unused) { i = first_cpu(cpu_online_map); while (1) { set_cpus_allowed(current, cpumask_of_cpu(i)); /* can block */ /* we should now be running on cpu i */ do_something_on_a_cpu(i); /* sleep for some time */ i = next_cpu(cpu, cpu_online_map); } } This thread makes absolutely -no- calls to try_to_freeze() in its lifetime. 1. Does this mean that the thread can't be frozen? (lets say that the thread's PF_NOFREEZE is not set) AFAICS it can still be frozen by sending it a signal and have the signal delivery code call try_to_freeze() .. 2. If the thread can be frozen at any arbitrary point of its execution, then I dont see what prevents cpu_online_map from changing under the feet of rtasd thread, In other words, we would have failed to provide the ability to *block* hotplug operations from happening concurrently. > All of them are forced to enter refrigerator(). ^^^^^^ *forced*, yes ..that's the point of concern .. Warm regards, vatsa - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/