linux-kernel - [PATCH 4.9 058/164] cxl: Force context lock during EEH flow

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Date:   Tue, 23 May 2017 22:07:55 +0200
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>,
        Vaibhav Jain <vaibhav@...ux.vnet.ibm.com>,
        Frederic Barrat <fbarrat@...ux.vnet.ibm.com>,
        "Matthew R. Ochs" <mrochs@...ux.vnet.ibm.com>,
        Uma Krishnan <ukrishn@...ux.vnet.ibm.com>,
        Michael Ellerman <mpe@...erman.id.au>
Subject: [PATCH 4.9 058/164] cxl: Force context lock during EEH flow

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

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

From: Vaibhav Jain <vaibhav@...ux.vnet.ibm.com>

commit ea9a26d117cf0637c71d3e0076f4a124bf5859df upstream.

During an eeh event when the cxl card is fenced and card sysfs attr
perst_reloads_same_image is set following warning message is seen in the
kernel logs:

  Adapter context unlocked with 0 active contexts
  ------------[ cut here ]------------
  WARNING: CPU: 12 PID: 627 at
  ../drivers/misc/cxl/main.c:325 cxl_adapter_context_unlock+0x60/0x80 [cxl]

Even though this warning is harmless, it clutters the kernel log
during an eeh event. This warning is triggered as the EEH callback
cxl_pci_error_detected doesn't obtain a context-lock before forcibly
detaching all active context and when context-lock is released during
call to cxl_configure_adapter from cxl_pci_slot_reset, a warning in
cxl_adapter_context_unlock is triggered.

To fix this warning, we acquire the adapter context-lock via
cxl_adapter_context_lock() in the eeh callback
cxl_pci_error_detected() once all the virtual AFU PHBs are notified
and their contexts detached. The context-lock is released in
cxl_pci_slot_reset() after the adapter is successfully reconfigured
and before the we call the slot_reset callback on slice attached
device-drivers.

Fixes: 70b565bbdb91 ("cxl: Prevent adapter reset if an active context exists")
Reported-by: Andrew Donnellan <andrew.donnellan@....ibm.com>
Signed-off-by: Vaibhav Jain <vaibhav@...ux.vnet.ibm.com>
Acked-by: Frederic Barrat <fbarrat@...ux.vnet.ibm.com>
Reviewed-by: Matthew R. Ochs <mrochs@...ux.vnet.ibm.com>
Tested-by: Uma Krishnan <ukrishn@...ux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@...erman.id.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/misc/cxl/pci.c |   19 +++++++++++++++++--
 1 file changed, 17 insertions(+), 2 deletions(-)

--- a/drivers/misc/cxl/pci.c
+++ b/drivers/misc/cxl/pci.c
@@ -1496,8 +1496,6 @@ static int cxl_configure_adapter(struct
 	if ((rc = cxl_native_register_psl_err_irq(adapter)))
 		goto err;

-	/* Release the context lock as adapter is configured */
-	cxl_adapter_context_unlock(adapter);
 	return 0;

 err:
@@ -1596,6 +1594,9 @@ static struct cxl *cxl_pci_init_adapter(
 	if ((rc = cxl_sysfs_adapter_add(adapter)))
 		goto err_put1;

+	/* Release the context lock as adapter is configured */
+	cxl_adapter_context_unlock(adapter);
+
 	return adapter;

 err_put1:
@@ -1893,6 +1894,13 @@ static pci_ers_result_t cxl_pci_error_de
 		cxl_ops->afu_deactivate_mode(afu, afu->current_mode);
 		pci_deconfigure_afu(afu);
 	}
+
+	/* should take the context lock here */
+	if (cxl_adapter_context_lock(adapter) != 0)
+		dev_warn(&adapter->dev,
+			 "Couldn't take context lock with %d active-contexts\n",
+			 atomic_read(&adapter->contexts_num));
+
 	cxl_deconfigure_adapter(adapter);

 	return result;
@@ -1911,6 +1919,13 @@ static pci_ers_result_t cxl_pci_slot_res
 	if (cxl_configure_adapter(adapter, pdev))
 		goto err;

+	/*
+	 * Unlock context activation for the adapter. Ideally this should be
+	 * done in cxl_pci_resume but cxlflash module tries to activate the
+	 * master context as part of slot_reset callback.
+	 */
+	cxl_adapter_context_unlock(adapter);
+
 	for (i = 0; i < adapter->slices; i++) {
 		afu = adapter->afu[i];