[Xen-devel] [RFC v3 1/4] Port WARN_ON_ONCE() from Linux

[Sameer Goel <sgoel@xxxxxxxxxxxxxx>]

Port WARN_ON_ONCE macro from Linux. A return value is expected from this
macro, so the implementation  does not follow the Xen convention of wrapping
macros in a do..while.
---
 xen/include/xen/lib.h | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/xen/include/xen/lib.h b/xen/include/xen/lib.h
index ed00ae1..83206c0 100644
--- a/xen/include/xen/lib.h
+++ b/xen/include/xen/lib.h
@@ -11,6 +11,17 @@
 #define BUG_ON(p)  do { if (unlikely(p)) BUG();  } while (0)
 #define WARN_ON(p) do { if (unlikely(p)) WARN(); } while (0)
 
+#define WARN_ON_ONCE(p)        ({                          \
+    static bool __section(".data.unlikely") __warned; \
+    int __ret_warn_once = !!(p);                    \
+                                                    \
+    if (unlikely(__ret_warn_once && !__warned)) {   \
+        __warned = true;                            \
+        WARN_ON(1);                                 \
+    }                                               \
+    unlikely(__ret_warn_once);                      \
+})
+
 #if __GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 6)
 /* Force a compilation error if condition is true */
 #define BUILD_BUG_ON(cond) ({ _Static_assert(!(cond), "!(" #cond ")"); })
-- 
Qualcomm Datacenter Technologies as an affiliate of Qualcomm Technologies, Inc. 
Qualcomm Technologies, Inc. is a member of the Code Aurora Forum, a Linux 
Foundation Collaborative Project.


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