git: 56557fd4c43a - stable/13 - linuxkpi: Add try_cmpxchg and atomic_try_cmpxchg

The branch stable/13 has been updated by manu:

URL: https://cgit.FreeBSD.org/src/commit/?id=56557fd4c43a9fb25200f2afff7a557eb2028845

commit 56557fd4c43a9fb25200f2afff7a557eb2028845
Author:     Emmanuel Vadot <manu@FreeBSD.org>
AuthorDate: 2022-07-27 07:41:04 +0000
Commit:     Emmanuel Vadot <manu@FreeBSD.org>
CommitDate: 2022-09-07 15:09:03 +0000

    linuxkpi: Add try_cmpxchg and atomic_try_cmpxchg
    
    Needed by drm-kmod
    
    Obtain from:    drm-kmod
    Sponsored by:   Beckhoff Automation GmbH & Co. KG
    Differential Revision:  https://reviews.freebsd.org/D36015
    
    (cherry picked from commit 39da3678b1ce2d4fac300e022e544b1db5c117c0)
---
 sys/compat/linuxkpi/common/include/asm/atomic.h | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

diff --git a/sys/compat/linuxkpi/common/include/asm/atomic.h b/sys/compat/linuxkpi/common/include/asm/atomic.h
index 7c7a2c4d4b92..d7e5338c0356 100644
--- a/sys/compat/linuxkpi/common/include/asm/atomic.h
+++ b/sys/compat/linuxkpi/common/include/asm/atomic.h
@@ -268,6 +268,28 @@ atomic_cmpxchg(atomic_t *v, int old, int new)
 	__ret.val;							\
 })
 
+#define try_cmpxchg(p, op, n)							\
+({										\
+	__typeof(p) __op = (__typeof((p)))(op);					\
+	__typeof(*(p)) __o = *__op;						\
+	__typeof(*(p)) __p = __sync_val_compare_and_swap((p), (__o), (n));	\
+	if (__p != __o)								\
+		*__op = __p;							\
+	(__p == __o);								\
+})
+
+#define __atomic_try_cmpxchg(type, _p, _po, _n)		\
+({							\
+	__typeof(_po) __po = (_po);			\
+	__typeof(*(_po)) __r, __o = *__po;		\
+	__r = atomic_cmpxchg##type((_p), __o, (_n));	\
+	if (unlikely(__r != __o))			\
+		*__po = __r;				\
+	likely(__r == __o);				\
+})
+
+#define	atomic_try_cmpxchg(_p, _po, _n)	__atomic_try_cmpxchg(, _p, _po, _n)
+
 static inline int
 atomic_dec_if_positive(atomic_t *v)
 {