[PATCH 8/8] x86/entry, bug: Comment the instrumentation_begin() usage for WARN()

From: Peter Zijlstra
Date: Thu Jun 04 2020 - 06:25:53 EST


Explain the rationale for annotating WARN(), even though, strictly
speaking printk() and friends are very much not safe in many of the
places we put them.

Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
---
arch/x86/include/asm/bug.h | 6 ++++++
1 file changed, 6 insertions(+)

--- a/arch/x86/include/asm/bug.h
+++ b/arch/x86/include/asm/bug.h
@@ -76,6 +76,12 @@ do { \
unreachable(); \
} while (0)

+/*
+ * This instrumentation_begin() is strictly speaking incorrect; but it
+ * suppresses the complaints from WARN()s in noinstr code. If such a WARN()
+ * were to trigger, we'd rather wreck the machine in an attempt to get the
+ * message out than not know about it.
+ */
#define __WARN_FLAGS(flags) \
do { \
instrumentation_begin(); \