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Subject[tip:core/urgent] WARN_ON_SMP(): Allow use in if() statements on UP
Commit-ID:  2092e6be82ec71ecbf5a8ceeef004bbcbdb78812
Gitweb: http://git.kernel.org/tip/2092e6be82ec71ecbf5a8ceeef004bbcbdb78812
Author: Steven Rostedt <srostedt@redhat.com>
AuthorDate: Thu, 17 Mar 2011 15:21:06 -0400
Committer: Ingo Molnar <mingo@elte.hu>
CommitDate: Fri, 25 Mar 2011 11:32:09 +0100

WARN_ON_SMP(): Allow use in if() statements on UP
Both WARN_ON() and WARN_ON_SMP() should be able to be used in
an if statement.

if (WARN_ON_SMP(foo)) { ... }
Because WARN_ON_SMP() is defined as a do { } while (0) on UP,
it can not be used this way.
Convert it to the same form that WARN_ON() is, even when
CONFIG_SMP is off.

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Acked-by: Darren Hart <dvhart@linux.intel.com>
Cc: Lai Jiangshan <laijs@cn.fujitsu.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
LKML-Reference: <20110317192208.444147791@goodmis.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
---
include/asm-generic/bug.h | 28 +++++++++++++++++++++++++++-
1 files changed, 27 insertions(+), 1 deletions(-)
diff --git a/include/asm-generic/bug.h b/include/asm-generic/bug.h
index c2c9ba0..f2d2faf 100644
--- a/include/asm-generic/bug.h
+++ b/include/asm-generic/bug.h
@@ -165,10 +165,36 @@ extern void warn_slowpath_null(const char *file, const int line);
#define WARN_ON_RATELIMIT(condition, state) \
WARN_ON((condition) && __ratelimit(state))

+/*
+ * WARN_ON_SMP() is for cases that the warning is either
+ * meaningless for !SMP or may even cause failures.
+ * This is usually used for cases that we have
+ * WARN_ON(!spin_is_locked(&lock)) checks, as spin_is_locked()
+ * returns 0 for uniprocessor settings.
+ * It can also be used with values that are only defined
+ * on SMP:
+ *
+ * struct foo {
+ * [...]
+ * #ifdef CONFIG_SMP
+ * int bar;
+ * #endif
+ * };
+ *
+ * void func(struct foo *zoot)
+ * {
+ * WARN_ON_SMP(!zoot->bar);
+ *
+ * For CONFIG_SMP, WARN_ON_SMP() should act the same as WARN_ON(),
+ * and should be a nop and return false for uniprocessor.
+ *
+ * if (WARN_ON_SMP(x)) returns true only when CONFIG_SMP is set
+ * and x is true.
+ */
#ifdef CONFIG_SMP
# define WARN_ON_SMP(x) WARN_ON(x)
#else
-# define WARN_ON_SMP(x) do { } while (0)
+# define WARN_ON_SMP(x) ({0;})
#endif

#endif

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