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| author | Paul E. McKenney <paulmck@kernel.org> | 2024-01-30 06:08:32 -0800 |
|---|---|---|
| committer | Paul E. McKenney <paulmck@kernel.org> | 2024-05-06 14:29:04 -0700 |
| commit | d372e20433cbc0b0e3e59c89ccb6618501fcf6af (patch) | |
| tree | ca44e27b0b24f40a5fb138fe00d84ec38da707c8 | |
| parent | 293f5bc2717b2178978c0d9ce9584da552279c3b (diff) | |
| download | linux-d372e20433cbc0b0e3e59c89ccb6618501fcf6af.tar.gz | |
Documentation/atomic_t: Emphasize that failed atomic operations give no ordering
The ORDERING section of Documentation/atomic_t.txt can easily be read as
saying that conditional atomic RMW operations that fail are ordered when
those operations have the _acquire() or _release() suffixes. This is
not the case, therefore update this section to make it clear that failed
conditional atomic RMW operations provide no ordering.
Reported-by: Anna-Maria Behnsen <anna-maria@linutronix.de>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Cc: Alan Stern <stern@rowland.harvard.edu>
Cc: Will Deacon <will@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Jade Alglave <j.alglave@ucl.ac.uk>
Cc: Luc Maranget <luc.maranget@inria.fr>
Cc: "Paul E. McKenney" <paulmck@kernel.org>
Cc: Akira Yokosawa <akiyks@gmail.com>
Cc: Daniel Lustig <dlustig@nvidia.com>
Cc: Joel Fernandes <joel@joelfernandes.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: <linux-arch@vger.kernel.org>
Cc: <linux-doc@vger.kernel.org>
Acked-by: Andrea Parri <parri.andrea@gmail.com>
Acked-by: Mark Rutland <mark.rutland@arm.com>
| -rw-r--r-- | Documentation/atomic_t.txt | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/Documentation/atomic_t.txt b/Documentation/atomic_t.txt index d7adc6d543db4f..bee3b1bca9a7b4 100644 --- a/Documentation/atomic_t.txt +++ b/Documentation/atomic_t.txt @@ -171,14 +171,14 @@ The rule of thumb: - RMW operations that are conditional are unordered on FAILURE, otherwise the above rules apply. -Except of course when an operation has an explicit ordering like: +Except of course when a successful operation has an explicit ordering like: {}_relaxed: unordered {}_acquire: the R of the RMW (or atomic_read) is an ACQUIRE {}_release: the W of the RMW (or atomic_set) is a RELEASE Where 'unordered' is against other memory locations. Address dependencies are -not defeated. +not defeated. Conditional operations are still unordered on FAILURE. Fully ordered primitives are ordered against everything prior and everything subsequent. Therefore a fully ordered primitive is like having an smp_mb() |