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authorPeter Zijlstra <peterz@infradead.org>2019-05-24 14:52:31 +0300
committerIngo Molnar <mingo@kernel.org>2019-06-03 13:32:57 +0300
commitfff9b6c7d26943a8eb32b58364b7ec6b9369746a (patch)
tree54d08e55187dcb948012ad5948e4b6e25621351b /Documentation/atomic_t.txt
parent6a6a9d5fb9f26d2c2127497f3a42adbeb5ccc2a4 (diff)
downloadlinux-fff9b6c7d26943a8eb32b58364b7ec6b9369746a.tar.xz
Documentation/atomic_t.txt: Clarify pure non-rmw usage
Clarify that pure non-RMW usage of atomic_t is pointless, there is nothing 'magical' about atomic_set() / atomic_read(). This is something that seems to confuse people, because I happen upon it semi-regularly. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Acked-by: Will Deacon <will.deacon@arm.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Link: https://lkml.kernel.org/r/20190524115231.GN2623@hirez.programming.kicks-ass.net Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'Documentation/atomic_t.txt')
-rw-r--r--Documentation/atomic_t.txt6
1 files changed, 4 insertions, 2 deletions
diff --git a/Documentation/atomic_t.txt b/Documentation/atomic_t.txt
index dca3fb0554db..89eae7f6b360 100644
--- a/Documentation/atomic_t.txt
+++ b/Documentation/atomic_t.txt
@@ -81,9 +81,11 @@ Non-RMW ops:
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.
+smp_store_release() respectively. 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.
-The one detail to this is that atomic_set{}() should be observable to the RMW
+A subtle detail of atomic_set{}() is that it should be observable to the RMW
ops. That is:
C atomic-set