Hi,
On 02/09/2018 10:29 AM, Roger Pau Monné wrote:
On Thu, Feb 08, 2018 at 08:10:49PM -0700, Sameer Goel wrote:
diff --git a/xen/include/xen/lib.h b/xen/include/xen/lib.h
index 1d9771340c..697212a061 100644
--- a/xen/include/xen/lib.h
+++ b/xen/include/xen/lib.h
@@ -11,6 +11,19 @@
#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); \
^ bool
+ \
+ if ( unlikely(__ret_warn_once && !__warned) ) \
+ { \
+ __warned = true; \
+ WARN(); \
+ } \
+ unlikely(__ret_warn_once); \
Does this macro really need to return something? It seems weird to me
to allow usages like: if ( WARN_ON_ONCE...
This construct is used in Linux (included in the driver ported):
if (WARN_ON_ONCE(fwspec->iommu_priv)) {
master = fwspec->iommu_priv;
smmu = master->smmu;
} else {
....
}
IHMO the makes the code nicer to read over:
WARN_ON_ONCE(...)
if ( ... ) {
} else {
}
Cheers,
--
Julien Grall
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