linux-kernel - [PATCH 4.2 022/134] cxl: Allow release of contexts which have been OPENED but not STARTED

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Date:	Sat, 26 Sep 2015 13:54:34 -0700
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org,
	Andrew Donnellan <andrew.donnellan@....ibm.com>,
	Daniel Axtens <dja@...ens.net>,
	Ian Munsie <imunsie@....ibm.com>,
	Michael Ellerman <mpe@...erman.id.au>
Subject: [PATCH 4.2 022/134] cxl: Allow release of contexts which have been OPENED but not STARTED

4.2-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Andrew Donnellan <andrew.donnellan@....ibm.com>

commit 7c26b9cf5347c24272152438cdd9675183804425 upstream.

If we open a context but do not start it (either because we do not attempt
to start it, or because it fails to start for some reason), we are left
with a context in state OPENED. Previously, cxl_release_context() only
allowed releasing contexts in state CLOSED, so attempting to release an
OPENED context would fail.

In particular, this bug causes available contexts to run out after some EEH
failures, where drivers attempt to release contexts that have failed to
start.

Allow releasing contexts in any state with a value lower than STARTED, i.e.
OPENED or CLOSED (we can't release a STARTED context as it's currently
using the hardware, and we assume that contexts in any new states which may
be added in future with a value higher than STARTED are also unsafe to
release).

Fixes: 6f7f0b3df6d4 ("cxl: Add AFU virtual PHB and kernel API")
Signed-off-by: Andrew Donnellan <andrew.donnellan@....ibm.com>
Signed-off-by: Daniel Axtens <dja@...ens.net>
Acked-by: Ian Munsie <imunsie@....ibm.com>
Signed-off-by: Michael Ellerman <mpe@...erman.id.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/misc/cxl/api.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/misc/cxl/api.c
+++ b/drivers/misc/cxl/api.c
@@ -59,7 +59,7 @@ EXPORT_SYMBOL_GPL(cxl_get_phys_dev);

 int cxl_release_context(struct cxl_context *ctx)
 {
-	if (ctx->status != CLOSED)
+	if (ctx->status >= STARTED)
 		return -EBUSY;

 	put_device(&ctx->afu->dev);

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