linux-kernel - [PATCH] random32: Use rcuidle variant for tracepoint

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Date:   Fri, 21 Aug 2020 08:30:43 +0200
From:   Marco Elver <elver@...gle.com>
To:     elver@...gle.com
Cc:     linux-kernel@...r.kernel.org, davem@...emloft.net, kuba@...nel.org,
        netdev@...r.kernel.org, Steven Rostedt <rostedt@...dmis.org>,
        Eric Dumazet <edumazet@...gle.com>,
        Peter Zijlstra <peterz@...radead.org>
Subject: [PATCH] random32: Use rcuidle variant for tracepoint

With KCSAN enabled, prandom_u32() may be called from any context,
including idle CPUs.

Therefore, switch to using trace_prandom_u32_rcuidle(), to avoid various
issues due to recursion and lockdep warnings when KCSAN and tracing is
enabled.

Fixes: 94c7eb54c4b8 ("random32: add a tracepoint for prandom_u32()")
Link: https://lkml.kernel.org/r/20200820155923.3d5c4873@oasis.local.home
Suggested-by: Steven Rostedt <rostedt@...dmis.org>
Signed-off-by: Marco Elver <elver@...gle.com>
Cc: Eric Dumazet <edumazet@...gle.com>
Cc: Peter Zijlstra <peterz@...radead.org>
---
 lib/random32.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lib/random32.c b/lib/random32.c
index 932345323af0..1c5607a411d4 100644
--- a/lib/random32.c
+++ b/lib/random32.c
@@ -83,7 +83,7 @@ u32 prandom_u32(void)
 	u32 res;
 
 	res = prandom_u32_state(state);
-	trace_prandom_u32(res);
+	trace_prandom_u32_rcuidle(res);
 	put_cpu_var(net_rand_state);
 
 	return res;
-- 
2.28.0.297.g1956fa8f8d-goog