[dm-devel] dm-table: delayed cleanup for dm_table_destroy()
mpatocka at redhat.com
Wed Mar 21 01:20:28 UTC 2012
On Tue, 20 Mar 2012, Mike Snitzer wrote:
> I once wanted to replace all msleep(1); with cpu_relax();:
> But Alasdair wasn't sure if cpu_relax() would provide the required
> delay effect:
cpu_relax() would basically kill the kernel if compiled without preempt.
cpu_relax() makes the current processor sleep for a little moment, but it
doesn't schedule a different process.
cpu_relax() is useful in spinlocks - so that process waiting on a spinlock
is not slowing down the other process on a CPU with hyperthreading.
There was another possibility --- replace msleep(1) with yield(). The
problem with yield() is that if the process has readltime priority and
calls yield(), it doesn't give CPU to a different process with a lower
priority. So it would cause deadlock if executed with realtime priority.
msleep(1) doesn't have this problem, so it's the best.
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