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From: Eddie James <eajames@linux.vnet.ibm.com>
To: openbmc@lists.ozlabs.org
Cc: joel@jms.id.au, andrew@aj.id.au, "Edward A. James" <eajames@us.ibm.com>
Subject: [PATCH linux dev-4.10 v5 31/31] drivers: hwmon: occ: Cancel occ
 operations in remove()
Date: Fri,  6 Oct 2017 09:29:08 -0500
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From: "Edward A. James" <eajames@us.ibm.com>

Prevent hanging forever waiting for OCC ops to complete.

Signed-off-by: Edward A. James <eajames@us.ibm.com>

Changes since v4:
 * Add comments for the spinlock
---
 drivers/hwmon/occ/p9_sbe.c | 49 +++++++++++++++++++++++++++++++++++++++-------
 1 file changed, 42 insertions(+), 7 deletions(-)

diff --git a/drivers/hwmon/occ/p9_sbe.c b/drivers/hwmon/occ/p9_sbe.c
index c7e0d9c..ac18422 100644
--- a/drivers/hwmon/occ/p9_sbe.c
+++ b/drivers/hwmon/occ/p9_sbe.c
@@ -14,37 +14,68 @@
 #include <linux/platform_device.h>
 #include <linux/occ.h>
 #include <linux/sched.h>
+#include <linux/spinlock.h>
 #include <linux/workqueue.h>
 
 struct p9_sbe_occ {
 	struct occ occ;
 	struct device *sbe;
+
+	/*
+	 * Pointer to occ device client. We store this so that we can cancel
+	 * the client operations in remove() if necessary. We only need one
+	 * pointer since we do one OCC operation (open, write, read, close) at
+	 * a time (access to p9_sbe_occ_send_cmd is locked in the common code
+	 * with occ.lock).
+	 */
+	struct occ_client *client;
+
+	/*
+	 * This lock controls access to the client pointer and ensures atomic
+	 * open, close and NULL assignment. This prevents simultaneous opening
+	 * and closing of the client, or closing multiple times.
+	 */
+	spinlock_t lock;
 };
 
 #define to_p9_sbe_occ(x)	container_of((x), struct p9_sbe_occ, occ)
 
+static void p9_sbe_occ_close_client(struct p9_sbe_occ *occ)
+{
+	struct occ_client *tmp_client;
+
+	spin_lock_irq(&occ->lock);
+	tmp_client = occ->client;
+	occ->client = NULL;
+	occ_drv_release(tmp_client);
+	spin_unlock_irq(&occ->lock);
+}
+
 static int p9_sbe_occ_send_cmd(struct occ *occ, u8 *cmd)
 {
 	int rc, error;
-	struct occ_client *client;
 	struct occ_response *resp = &occ->resp;
 	struct p9_sbe_occ *p9_sbe_occ = to_p9_sbe_occ(occ);
 
-	client = occ_drv_open(p9_sbe_occ->sbe, 0);
-	if (!client) {
+	spin_lock_irq(&p9_sbe_occ->lock);
+	if (p9_sbe_occ->sbe)
+		p9_sbe_occ->client = occ_drv_open(p9_sbe_occ->sbe, 0);
+	spin_unlock_irq(&p9_sbe_occ->lock);
+
+	if (!p9_sbe_occ->client) {
 		rc = -ENODEV;
 		goto assign;
 	}
 
-	rc = occ_drv_write(client, (const char *)&cmd[1], 7);
+	rc = occ_drv_write(p9_sbe_occ->client, (const char *)&cmd[1], 7);
 	if (rc < 0)
 		goto err;
 
-	rc = occ_drv_read(client, (char *)resp, sizeof(*resp));
+	rc = occ_drv_read(p9_sbe_occ->client, (char *)resp, sizeof(*resp));
 	if (rc < 0)
 		goto err;
 
-	occ_drv_release(client);
+	p9_sbe_occ_close_client(p9_sbe_occ);
 
 	switch (resp->return_status) {
 	case RESP_RETURN_CMD_IN_PRG:
@@ -72,7 +103,7 @@ static int p9_sbe_occ_send_cmd(struct occ *occ, u8 *cmd)
 	goto done;
 
 err:
-	occ_drv_release(client);
+	p9_sbe_occ_close_client(p9_sbe_occ);
 	dev_err(occ->bus_dev, "occ bus op failed rc:%d\n", rc);
 assign:
 	error = rc;
@@ -132,6 +163,7 @@ static int p9_sbe_occ_probe(struct platform_device *pdev)
 	p9_sbe_occ->sbe = pdev->dev.parent;
 
 	occ = &p9_sbe_occ->occ;
+	spin_lock_init(&p9_sbe_occ->lock);
 	occ->bus_dev = &pdev->dev;
 	occ->groups[0] = &occ->group;
 	occ->poll_cmd_data = 0x20;
@@ -152,7 +184,10 @@ static int p9_sbe_occ_probe(struct platform_device *pdev)
 static int p9_sbe_occ_remove(struct platform_device *pdev)
 {
 	struct occ *occ = platform_get_drvdata(pdev);
+	struct p9_sbe_occ *p9_sbe_occ = to_p9_sbe_occ(occ);
 
+	p9_sbe_occ->sbe = NULL;
+	p9_sbe_occ_close_client(p9_sbe_occ);
 	occ_remove_status_attrs(occ);
 
 	atomic_dec(&occ_num_occs);
-- 
1.8.3.1