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| author | Peter Zijlstra <peterz@infradead.org> | 2019-05-24 13:52:31 +0200 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2019-06-03 12:32:57 +0200 |
| commit | fff9b6c7d26943a8eb32b58364b7ec6b9369746a (patch) | |
| tree | 54d08e55187dcb948012ad5948e4b6e25621351b /Documentation/atomic_t.txt | |
| parent | 6a6a9d5fb9f26d2c2127497f3a42adbeb5ccc2a4 (diff) | |
| download | lwn-fff9b6c7d26943a8eb32b58364b7ec6b9369746a.tar.gz lwn-fff9b6c7d26943a8eb32b58364b7ec6b9369746a.zip | |
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.txt | 6 |
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 |