linux-kernel - [PATCH 2/5] Modify behaviour of request_*muxed

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Message-Id: <20170621035349.4125-3-zboszor@pr.hu>
Date:   Wed, 21 Jun 2017 05:53:46 +0200
From:   Zoltán Böszörményi 
        <zboszor@...hu>
To:     linux-kernel@...r.kernel.org
Cc:     linux-usb@...r.kernel.org, linux-watchdog@...r.kernel.org,
        linux-i2c@...r.kernel.org,
        Paul Menzel <paulepanter@...rs.sourceforge.net>,
        Christian Fetzer <fetzer.ch@...il.com>,
        Jean Delvare <jdelvare@...e.com>,
        Nehal Shah <nehal-bakulchandra.shah@....com>,
        Tim Small <tim@...ss.co.uk>,
        Guenter Roeck <linux@...ck-us.net>, kernel@...ss.net,
        wim@...ana.be, jlayton@...chiereds.net, marc.2377@...il.com,
        cshorler@...glemail.com, wsa@...-dreams.de,
        regressions@...mhuis.info,
        Zoltán Böszörményi 
        <zboszor@...hu>
Subject: [PATCH 2/5] Modify behaviour of request_*muxed_region()

In order to make request_*muxed_region() behave more like mutex_lock(),
a possible failure case needs to be eliminated. When drivers do not
properly share the same I/O region, e.g. one is using request_region()
and the other is using request_muxed_region(), the kernel didn't
warn the user about it. This change modifies IORESOURCE_MUXED behaviour
so it always goes to sleep waiting for the resuorce to be freed
and the inconsistent resource flag usage is logged with KERN_ERR.

Signed-off-by: Zoltán Böszörményi <zboszor@...hu>
---
 kernel/resource.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/kernel/resource.c b/kernel/resource.c
index 220f695..59fa426 100644
--- a/kernel/resource.c
+++ b/kernel/resource.c
@@ -1150,7 +1150,9 @@ struct resource * __request_declared_region(struct resource *parent,
 				continue;
 			}
 		}
-		if (conflict->flags & flags & IORESOURCE_MUXED) {
+		if (flags & IORESOURCE_MUXED) {
+			if (!(conflict->flags & IORESOURCE_MUXED))
+				printk(KERN_ERR "Resource conflict between muxed \"%s\" and non-muxed \"%s\" I/O regions!\n", res->name, conflict->name);
 			add_wait_queue(&muxed_resource_wait, &wait);
 			write_unlock(&resource_lock);
 			set_current_state(TASK_UNINTERRUPTIBLE);
-- 
2.9.4