On Fri, May 24, 2019 at 01:18:07PM +0200, Peter Zijlstra wrote:
On Fri, May 24, 2019 at 12:37:31PM +0200, Peter Zijlstra wrote:
On Thu, May 23, 2019 at 11:19:26AM +0100, Mark Rutland wrote:
[mark@lakrids:~/src/linux]% git grep '(return|=)\s+atomic(64)?_set' include/linux/vmw_vmci_defs.h: return atomic_set((atomic_t *)var, (u32)new_val); include/linux/vmw_vmci_defs.h: return atomic64_set(var, new_val);
Oh boy, what a load of crap you just did find.
How about something like the below? I've not read how that buffer is used, but the below preserves all broken without using atomic*_t.
Clarified by something along these lines?
Documentation/atomic_t.txt | 3 +++ 1 file changed, 3 insertions(+)
diff --git a/Documentation/atomic_t.txt b/Documentation/atomic_t.txt index dca3fb0554db..125c95ddbbc0 100644 --- a/Documentation/atomic_t.txt +++ b/Documentation/atomic_t.txt @@ -83,6 +83,9 @@ The non-RMW ops are (typically) regular LOADs and STOREs and are canonically implemented using READ_ONCE(), WRITE_ONCE(), smp_load_acquire() and smp_store_release() respectively.
Not sure you need a new paragraph here.
+Therefore, if you find yourself only using the Non-RMW operations of atomic_t, +you do not in fact need atomic_t at all and are doing it wrong.
That makes sense to me, although I now find that the sentence below is a bit confusing because it sounds like it's a caveat relating to only using Non-RMW ops.
The one detail to this is that atomic_set{}() should be observable to the RMW ops. That is:
How about changing this to be:
"A subtle detail of atomic_set{}() is that it should be observable..."
With that:
Acked-by: Will Deacon will.deacon@arm.com
Will