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Subject: Re: [PATCH linux dev-4.10 v5 31/31] drivers: hwmon: occ: Cancel occ
 operations in remove()
To: Joel Stanley <joel@jms.id.au>
Cc: Andrew Jeffery <andrew@aj.id.au>, "Edward A. James" <eajames@us.ibm.com>, 
 OpenBMC Maillist <openbmc@lists.ozlabs.org>
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From: Eddie James <eajames@linux.vnet.ibm.com>
Date: Mon, 9 Oct 2017 09:33:44 -0500
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On 10/08/2017 09:00 PM, Joel Stanley wrote:
> On Fri, Oct 6, 2017 at 11:59 PM, Eddie James <eajames@linux.vnet.ibm.com> wrote:
>> 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);
> Why not spin_lock_irqsave/spin_unlock_irqsave? Same throughout this patch.

Well spin_lock_irq/spin_unlock_irq is used through the occ and sbefifo 
drivers. Just following suit here. I can switch it if necessary.

Thanks,
Eddie

>
> Cheers,
>
> Joel
>
>> +       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
>>