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[PATCH 2/5 v2] Modify behaviour of request_*muxed_region()

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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.

v2: Fixed checkpatch.pl warnings and extended the comment
    about request_declared_muxed_region.

Signed-off-by: Zoltán Böszörményi <zboszor@pr.hu>
---
 kernel/resource.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/kernel/resource.c b/kernel/resource.c
index 2be7029..5df2731 100644
--- a/kernel/resource.c
+++ b/kernel/resource.c
@@ -1125,6 +1125,7 @@ resource_size_t resource_alignment(struct resource *res)
  *
  * request_declared_muxed_region creates a new shared busy region
  * described in an existing resource descriptor.
+ * It only returns if it succeeded.
  *
  * release_region releases a matching busy region.
  * The region is only freed if it was allocated.
@@ -1191,7 +1192,10 @@ struct resource *__request_declared_region(struct resource *parent,
 				continue;
 			}
 		}
-		if (conflict->flags & flags & IORESOURCE_MUXED) {
+		if (flags & IORESOURCE_MUXED) {
+			if (!(conflict->flags & IORESOURCE_MUXED))
+				pr_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

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[PATCH 0/5 v3] Fix sp5100_tco watchdog driver regression Zoltán Böszörményi          <zboszor@pr.hu> - 2017-06-21 06:10 +0200
  [PATCH 3/5] usb: pci-quirks: Protect the I/O port pair of SB800 Zoltán Böszörményi          <zboszor@pr.hu> - 2017-06-21 06:10 +0200
  [PATCH 2/5] Modify behaviour of request_*muxed_region() Zoltán Böszörményi          <zboszor@pr.hu> - 2017-06-21 06:10 +0200
  [PATCH 5/5] watchdog: sp5100_tco: Use request_declared_muxed_region() Zoltán Böszörményi          <zboszor@pr.hu> - 2017-06-21 06:10 +0200
    Re: [PATCH 5/5] watchdog: sp5100_tco: Use  request_declared_muxed_region() Guenter Roeck <linux@roeck-us.net> - 2017-06-21 17:10 +0200
  [PATCH 1/5] Extend the request_region() infrastructure Zoltán Böszörményi          <zboszor@pr.hu> - 2017-06-21 06:10 +0200
  [PATCH 4/5] i2c: i2c-piix4: Use request_declared_muxed_region() Zoltán Böszörményi          <zboszor@pr.hu> - 2017-06-21 06:10 +0200
  [PATCH 1/5 v2] Extend the request_region() infrastructure Zoltán Böszörményi          <zboszor@pr.hu> - 2017-06-22 15:30 +0200
  [PATCH 0/5 v4] Fix sp5100_tco watchdog driver regression Zoltán Böszörményi          <zboszor@pr.hu> - 2017-06-22 15:30 +0200
    [PATCH 2/5 v2] Modify behaviour of request_*muxed_region() Zoltán Böszörményi          <zboszor@pr.hu> - 2017-06-22 15:30 +0200
    [PATCH 3/5 v4] usb: pci-quirks: Protect the I/O port pair of SB800 Zoltán Böszörményi          <zboszor@pr.hu> - 2017-06-22 15:30 +0200
    [PATCH 4/5 v4] i2c: i2c-piix4: Use request_declared_muxed_region() Zoltán Böszörményi          <zboszor@pr.hu> - 2017-06-22 15:30 +0200
    [PATCH 5/5 v4] watchdog: sp5100_tco: Use request_declared_muxed_region() Zoltán Böszörményi          <zboszor@pr.hu> - 2017-06-22 15:30 +0200

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