diff options
| author | Linus Torvalds <torvalds@linux-foundation.org> | 2023-11-09 22:22:13 -0800 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2023-11-22 09:32:49 -0800 |
| commit | 125b0bb95dd6bec81b806b997a4ccb026eeecf8f (patch) | |
| tree | 9a4bb22f59d45588de93b7298cdefbbfd63b6f8b /include | |
| parent | c2d5304e6c648ebcf653bace7e51e0e6742e46c8 (diff) | |
asm-generic: qspinlock: fix queued_spin_value_unlocked() implementation
We really don't want to do atomic_read() or anything like that, since we
already have the value, not the lock. The whole point of this is that
we've loaded the lock from memory, and we want to check whether the
value we loaded was a locked one or not.
The main use of this is the lockref code, which loads both the lock and
the reference count in one atomic operation, and then works on that
combined value. With the atomic_read(), the compiler would pointlessly
spill the value to the stack, in order to then be able to read it back
"atomically".
This is the qspinlock version of commit c6f4a9002252 ("asm-generic:
ticket-lock: Optimize arch_spin_value_unlocked()") which fixed this same
bug for ticket locks.
Cc: Guo Ren <guoren@kernel.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Waiman Long <longman@redhat.com>
Link: https://lore.kernel.org/all/CAHk-=whNRv0v6kQiV5QO6DJhjH4KEL36vWQ6Re8Csrnh4zbRkQ@mail.gmail.com/
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include')
| -rw-r--r-- | include/asm-generic/qspinlock.h | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/include/asm-generic/qspinlock.h b/include/asm-generic/qspinlock.h index 995513fa2690..0655aa5b57b2 100644 --- a/include/asm-generic/qspinlock.h +++ b/include/asm-generic/qspinlock.h @@ -70,7 +70,7 @@ static __always_inline int queued_spin_is_locked(struct qspinlock *lock) */ static __always_inline int queued_spin_value_unlocked(struct qspinlock lock) { - return !atomic_read(&lock.val); + return !lock.val.counter; } /** |