[xen master] xen: Rework WARN_ON() to return whether a warning was triggered

[patchbot@xxxxxxx]

commit 8c8938dcc1bd37dd61f705410053e08804ca2b55
Author:     Julien Grall <jgrall@xxxxxxxxxx>
AuthorDate: Fri Dec 18 13:30:54 2020 +0000
Commit:     Stefano Stabellini <sstabellini@xxxxxxxxxx>
CommitDate: Mon Dec 21 14:39:38 2020 -0800

    xen: Rework WARN_ON() to return whether a warning was triggered
    
    So far, our implementation of WARN_ON() cannot be used in the following
    situation:
    
    if ( WARN_ON() )
        ...
    
    This is because WARN_ON() doesn't return whether a warning has been
    triggered. Such construciton can be handy if you want to print more
    information and also dump the stack trace.
    
    Therefore, rework the WARN_ON() implementation to return whether a
    warning was triggered. The idea was borrowed from Linux
    
    Signed-off-by: Julien Grall <jgrall@xxxxxxxxxx>
    Reviewed-by: Juergen Gross <jgross@xxxxxxxx>
    Reviewed-by: Bertrand Marquis <bertrand.marquis@xxxxxxx>
    Acked-by: Stefano Stabellini <sstabellini@xxxxxxxxxx>
    Acked-by: Jan Beulich <jbeulich@xxxxxxxx>
---
 xen/include/xen/lib.h | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/xen/include/xen/lib.h b/xen/include/xen/lib.h
index 48429b69b8..5841bd489c 100644
--- a/xen/include/xen/lib.h
+++ b/xen/include/xen/lib.h
@@ -23,7 +23,13 @@
 #include <asm/bug.h>
 
 #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(p)  ({                  \
+    bool ret_warn_on_ = (p);            \
+                                        \
+    if ( unlikely(ret_warn_on_) )       \
+        WARN();                         \
+    unlikely(ret_warn_on_);             \
+})
 
 /* All clang versions supported by Xen have _Static_assert. */
 #if defined(__clang__) || \
--
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