git: 71d815861f1c - stable/13 - LinuxKPI: Change flags parameter type of atomic_dec_and_lock_irqsave

[Vladimir Kondratyev]

The branch stable/13 has been updated by wulf:

URL: https://cgit.FreeBSD.org/src/commit/?id=71d815861f1cd0281443a216998c23000fb4b301

commit 71d815861f1cd0281443a216998c23000fb4b301
Author:     Vladimir Kondratyev <wulf at FreeBSD.org>
AuthorDate: 2021-07-05 00:19:01 +0000
Commit:     Vladimir Kondratyev <wulf at FreeBSD.org>
CommitDate: 2021-07-20 22:43:52 +0000

    LinuxKPI: Change flags parameter type of atomic_dec_and_lock_irqsave
    
    On Linux atomic_dec_and_lock_irqsave is a wrapper macro which provides
    a reference to third parameter rather than parameter value itself to
    implementation routine called _atomic_dec_and_lock_irqsave [1].
    
    While here, implement a fast path.
    
    [1] https://github.com/torvalds/linux/blob/master/include/linux/spinlock.h#L476
    
    Reviewed by:    hselasky
    Differential revision:  https://reviews.freebsd.org/D30781
    
    (cherry picked from commit c77ec79b57aa92b428b940ed550a4a14ed44da48)
---
 sys/compat/linuxkpi/common/include/linux/spinlock.h | 17 +++++++++++------
 1 file changed, 11 insertions(+), 6 deletions(-)

diff --git a/sys/compat/linuxkpi/common/include/linux/spinlock.h b/sys/compat/linuxkpi/common/include/linux/spinlock.h
index 458d8d9f8da9..56eaecfb4cd6 100644
--- a/sys/compat/linuxkpi/common/include/linux/spinlock.h
+++ b/sys/compat/linuxkpi/common/include/linux/spinlock.h
@@ -168,15 +168,20 @@ spin_lock_destroy(spinlock_t *lock)
 	mtx_assert(&(_l)->m, MA_OWNED);		\
 } while (0)
 
+#define	atomic_dec_and_lock_irqsave(cnt, lock, flags) \
+	_atomic_dec_and_lock_irqsave(cnt, lock, &(flags))
 static inline int
-atomic_dec_and_lock_irqsave(atomic_t *cnt, spinlock_t *lock,
-    unsigned long flags)
+_atomic_dec_and_lock_irqsave(atomic_t *cnt, spinlock_t *lock,
+    unsigned long *flags)
 {
-	spin_lock_irqsave(lock, flags);
+	if (atomic_add_unless(cnt, -1, 1))
+		return (0);
+
+	spin_lock_irqsave(lock, *flags);
 	if (atomic_dec_and_test(cnt))
-		return 1;
-	spin_unlock_irqrestore(lock, flags);
-	return 0;
+		return (1);
+	spin_unlock_irqrestore(lock, *flags);
+	return (0);
 }
 
 #endif					/* _LINUX_SPINLOCK_H_ */