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
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