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Date:   Wed,  2 Nov 2022 12:06:10 +0100
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Message-ID: <20221102110611.1085175-4-glider@google.com>
Subject: [PATCH 4/5] kmsan: make sure PREEMPT_RT is off
From:   Alexander Potapenko <glider@google.com>
To:     glider@google.com
Cc:     linux-kernel@vger.kernel.org, linux-mm@kvack.org,
        Andrew Morton <akpm@linux-foundation.org>,
        Dmitry Vyukov <dvyukov@google.com>,
        Marco Elver <elver@google.com>,
        Peter Zijlstra <peterz@infradead.org>
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As pointed out by Peter Zijlstra, __msan_poison_alloca() does not play
well with IRQ code when PREEMPT_RT is on, because in that mode even
GFP_ATOMIC allocations cannot be performed.

Fixing this would require making stackdepot completely lockless, which
is quite challenging and may be excessive for the time being.

Instead, make sure KMSAN is incompatible with PREEMPT_RT, like other
debug configs are.

Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Marco Elver <elver@google.com>
Cc: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/lkml/20221025221755.3810809-1-glider@google.com/
Signed-off-by: Alexander Potapenko <glider@google.com>
---
 lib/Kconfig.kmsan | 1 +
 1 file changed, 1 insertion(+)

diff --git a/lib/Kconfig.kmsan b/lib/Kconfig.kmsan
index b2489dd6503fa..ef2c8f256c57d 100644
--- a/lib/Kconfig.kmsan
+++ b/lib/Kconfig.kmsan
@@ -12,6 +12,7 @@ config KMSAN
 	bool "KMSAN: detector of uninitialized values use"
 	depends on HAVE_ARCH_KMSAN && HAVE_KMSAN_COMPILER
 	depends on SLUB && DEBUG_KERNEL && !KASAN && !KCSAN
+	depends on !PREEMPT_RT
 	select STACKDEPOT
 	select STACKDEPOT_ALWAYS_INIT
 	help
-- 
2.38.1.273.g43a17bfeac-goog