Messages in this thread | | | Date | Tue, 5 Jun 2018 16:43:04 +0200 | From | Peter Zijlstra <> | Subject | Re: [PATCH 1/7] atomics/tty: add missing atomic_long_t * cast |
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On Tue, Jun 05, 2018 at 04:20:51PM +0200, Greg Kroah-Hartman wrote: > I think Peter Hurley was just trying to hid the atomic mess behind > function calls, which is why he didn't open-code it like you did here.
No reason to then not use the right types though. I mean, you can still use the helper functions, but I figured they weren't worth the bother. Esp. then using try_cmpxchg (which is relatively new) the helpers became very thin.
> But this makes it a bit more obvious as to what "magic" is happening, so > I like it.
Well, it also fixes one additional bug in that the old code used a regular unsigned long load of the value:
- long count = sem->count; + long count = atomic_long_read(&sem->count);
which doesn't guarantee enough. The atomic_long_read() thing implies READ_ONCE() which ensures the load is single copy atomic (GCC used to guarantee that for regular loads/stores to naturally aligned native words, but no longer).
> Care to turn it into a real patch so I can queue it up after 4.18-rc1 is > out? Or do you want me to do that?
I can make a proper patch, hold on.
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