[PATCH] cxl: Fix refcounting in kernel API

[PATCH] cxl: Fix refcounting in kernel API

[Michael Neuling]

Currently the kernel API AFU dev refcounting is done on context start and stop.
This patch moves this refcounting to context init and release, bringing it
inline with how the userspace API does it.

Without this we've seen the refcounting on the AFU get out of whack between the
user and kernel API usage.  This causes the AFU structures to be freed when
they are actually still in use.

This fixes some kref warnings we've been seeing and spurious ErrIVTE IRQs.

Signed-off-by: Michael Neuling <mikey@neuling.org>
---
mpe: This is for 4.2 fixes

 drivers/misc/cxl/api.c | 12 +++++-------
 1 file changed, 5 insertions(+), 7 deletions(-)

diff --git a/drivers/misc/cxl/api.c b/drivers/misc/cxl/api.c
index 0c77240..729e085 100644
--- a/drivers/misc/cxl/api.c
+++ b/drivers/misc/cxl/api.c
@@ -23,6 +23,7 @@ struct cxl_context *cxl_dev_context_init(struct pci_dev *dev)
 
 	afu = cxl_pci_to_afu(dev);
 
+	get_device(&afu->dev);
 	ctx = cxl_context_alloc();
 	if (IS_ERR(ctx))
 		return ctx;
@@ -31,6 +32,7 @@ struct cxl_context *cxl_dev_context_init(struct pci_dev *dev)
 	rc = cxl_context_init(ctx, afu, false, NULL);
 	if (rc) {
 		kfree(ctx);
+		put_device(&afu->dev);
 		return ERR_PTR(-ENOMEM);
 	}
 	cxl_assign_psn_space(ctx);
@@ -60,6 +62,8 @@ int cxl_release_context(struct cxl_context *ctx)
 	if (ctx->status != CLOSED)
 		return -EBUSY;
 
+	put_device(&ctx->afu->dev);
+
 	cxl_context_free(ctx);
 
 	return 0;
@@ -159,7 +163,6 @@ int cxl_start_context(struct cxl_context *ctx, u64 wed,
 	}
 
 	ctx->status = STARTED;
-	get_device(&ctx->afu->dev);
 out:
 	mutex_unlock(&ctx->status_mutex);
 	return rc;
@@ -175,12 +178,7 @@ EXPORT_SYMBOL_GPL(cxl_process_element);
 /* Stop a context.  Returns 0 on success, otherwise -Errno */
 int cxl_stop_context(struct cxl_context *ctx)
 {
-	int rc;
-
-	rc = __detach_context(ctx);
-	if (!rc)
-		put_device(&ctx->afu->dev);
-	return rc;
+	return __detach_context(ctx);
 }
 EXPORT_SYMBOL_GPL(cxl_stop_context);
 
-- 
2.1.0

Re: [PATCH] cxl: Fix refcounting in kernel API

[Ian Munsie]

Acked-by: Ian Munsie <imunsie@au1.ibm.com>

Re: cxl: Fix refcounting in kernel API

[Michael Ellerman]

On Tue, 2015-07-07 at 01:01:17 UTC, Michael Neuling wrote:
> Currently the kernel API AFU dev refcounting is done on context start and stop.
> This patch moves this refcounting to context init and release, bringing it
> inline with how the userspace API does it.
> 
> Without this we've seen the refcounting on the AFU get out of whack between the
> user and kernel API usage.  This causes the AFU structures to be freed when
> they are actually still in use.
> 
> This fixes some kref warnings we've been seeing and spurious ErrIVTE IRQs.
> 
> Signed-off-by: Michael Neuling <mikey@neuling.org>
> Acked-by: Ian Munsie <imunsie@au1.ibm.com>

Applied to powerpc fixes, thanks.

https://git.kernel.org/cgit/linux/kernel/git/powerpc/linux.git/commit/?h=fixes&id=3f8dc44d88d3e86178eb9322c779c599f3745b21

cheers