linux-kernel - [PATCH] module: Annotate nested sleep in resolve

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Message-ID: <20150210170604.GA21418@twins.programming.kicks-ass.net>
Date:	Tue, 10 Feb 2015 18:06:04 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Dave Jones <davej@...emonkey.org.uk>,
	Linux Kernel <linux-kernel@...r.kernel.org>
Cc:	Rusty Russell <rusty@...tcorp.com.au>
Subject: [PATCH] module: Annotate nested sleep in resolve_symbol()


Because wait_event() loops are safe vs spurious wakeups we can allow the
occasional sleep -- which ends up being very similar.

Cc: Rusty Russell <rusty@...tcorp.com.au>
Reported-by: Dave Jones <davej@...emonkey.org.uk>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
---
 kernel/module.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/kernel/module.c b/kernel/module.c
index d856e96a3cce..11d3bc18157e 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -1225,6 +1225,12 @@ static const struct kernel_symbol *resolve_symbol(struct module *mod,
 	const unsigned long *crc;
 	int err;
 
+	/*
+	 * The module_mutex should not be a heavily contended lock;
+	 * if we get the occasional sleep here, we'll go an extra iteration
+	 * in the wait_event_interruptible(), which is harmless.
+	 */
+	sched_annotate_sleep();
 	mutex_lock(&module_mutex);
 	sym = find_symbol(name, &owner, &crc,
 			  !(mod->taints & (1 << TAINT_PROPRIETARY_MODULE)), true);
--
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