Ilpo Järvinen wrote:
On Thu, 16 Aug 2007, Herbert Xu wrote:
quoted
We've been through that already. If it's a busy-wait it
should use cpu_relax.
I looked around a bit by using some command lines and ended up wondering if these are equal to busy-wait case (and should be fixed) or not:
./drivers/telephony/ixj.c
6674: while (atomic_read(&j->DSPWrite) > 0)
6675- atomic_dec(&j->DSPWrite);
...besides that, there are couple of more similar cases in the same file (with braces)...
atomic_dec() already has volatile behavior everywhere, so this is semantically okay, but this code (and any like it) should be calling cpu_relax() each iteration through the loop, unless there's a compelling reason not to. I'll allow that for some hardware drivers (possibly this one) such a compelling reason may exist, but hardware-independent core subsystems probably have no excuse.
If the maintainer of this code doesn't see a compelling reason to add cpu_relax() in this loop, then it should be patched.
-- Chris