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From: Hans Petter Selasky <hselasky@FreeBSD.org>
Date: Mon, 6 Aug 2018 08:40:02 +0000 (UTC)
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Subject: svn commit: r337374 - head/sys/compat/linuxkpi/common/include/asm
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Author: hselasky
Date: Mon Aug  6 08:40:02 2018
New Revision: 337374
URL: https://svnweb.freebsd.org/changeset/base/337374

Log:
  Implement atomic_long_cmpxchg() function in the LinuxKPI.
  
  Submitted by:	Johannes Lundberg <johalun0@gmail.com>
  MFC after:	1 week
  Sponsored by:	Mellanox Technologies

Modified:
  head/sys/compat/linuxkpi/common/include/asm/atomic-long.h

Modified: head/sys/compat/linuxkpi/common/include/asm/atomic-long.h
==============================================================================
--- head/sys/compat/linuxkpi/common/include/asm/atomic-long.h	Mon Aug  6 08:35:16 2018	(r337373)
+++ head/sys/compat/linuxkpi/common/include/asm/atomic-long.h	Mon Aug  6 08:40:02 2018	(r337374)
@@ -81,6 +81,21 @@ atomic_long_xchg(atomic_long_t *v, long val)
 	return atomic_swap_long(&v->counter, val);
 }
 
+static inline long
+atomic_long_cmpxchg(atomic_long_t *v, long old, long new)
+{
+	long ret = old;
+
+	for (;;) {
+		if (atomic_cmpset_long(&v->counter, old, new))
+			break;
+		ret = READ_ONCE(v->counter);
+		if (ret != old)
+			break;
+	}
+	return (ret);
+}
+
 static inline int
 atomic_long_add_unless(atomic_long_t *v, long a, long u)
 {