staging: unisys: visorhba: fail gracefully for thread creation failures

Previously, if visorhba ever failed to create its thread, it would have
subsequently attempted to do a kthread_stop() on an invalid task_struct
pointer.  This was fixed via the new visor_thread_stop() function, which
validates the task_struct pointer before doing the kthread_stop().

Also, the other thread-related fields in visor_thread_info (has_stopped
and id) were not being used, so visor_thead_info was just removed.

We also now spit out an error message if thread creation fails.

Signed-off-by: Tim Sell <Timothy.Sell@unisys.com>
Signed-off-by: David Kershner <david.kershner@unisys.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/staging/unisys/visorhba/visorhba_main.c b/drivers/staging/unisys/visorhba/visorhba_main.c
index 6f53f3d535542d8058cbab06fb0e6ac82058d1bc..176bcc35ba0e6e5dd2814e229cea776d3ed70f33 100644 (file)
--- a/drivers/staging/unisys/visorhba/visorhba_main.c
+++ b/drivers/staging/unisys/visorhba/visorhba_main.c
@@ -85,12 +85,6 @@ static struct visor_driver visorhba_driver = {
 MODULE_DEVICE_TABLE(visorbus, visorhba_channel_types);
 MODULE_ALIAS("visorbus:" SPAR_VHBA_CHANNEL_PROTOCOL_UUID_STR);
 
-struct visor_thread_info {
-       struct task_struct *task;
-       struct completion has_stopped;
-       int id;
-};
-
 struct visordisk_info {
        u32 valid;
        u32 channel, id, lun;   /* Disk Path */
@@ -137,7 +131,7 @@ struct visorhba_devdata {
        struct visordisk_info head;
        unsigned int max_buff_len;
        int devnum;
-       struct visor_thread_info threadinfo;
+       struct task_struct *thread;
        int thread_wait_ms;
 };
 
@@ -154,28 +148,36 @@ static struct visorhba_devices_open visorhbas_open[VISORHBA_OPEN_MAX];
                    (iter->lun == match->lun))
 /**
  *     visor_thread_start - starts a thread for the device
- *     @thrinfo: The thread to start
  *     @threadfn: Function the thread starts
  *     @thrcontext: Context to pass to the thread, i.e. devdata
  *     @name: string describing name of thread
  *
  *     Starts a thread for the device.
  *
- *     Return 0 on success;
+ *     Return the task_struct * denoting the thread on success,
+ *             or NULL on failure
  */
-static int visor_thread_start(struct visor_thread_info *thrinfo,
-                             int (*threadfn)(void *),
-                             void *thrcontext, char *name)
+static struct task_struct *visor_thread_start
+(int (*threadfn)(void *), void *thrcontext, char *name)
 {
-       /* used to stop the thread */
-       init_completion(&thrinfo->has_stopped);
-       thrinfo->task = kthread_run(threadfn, thrcontext, "%s", name);
-       if (IS_ERR(thrinfo->task)) {
-               thrinfo->id = 0;
-               return PTR_ERR(thrinfo->task);
+       struct task_struct *task;
+
+       task = kthread_run(threadfn, thrcontext, "%s", name);
+       if (IS_ERR(task)) {
+               pr_err("visorbus failed to start thread\n");
+               return NULL;
        }
-       thrinfo->id = thrinfo->task->pid;
-       return 0;
+       return task;
+}
+
+/**
+ *      visor_thread_stop - stops the thread if it is running
+ */
+static void visor_thread_stop(struct task_struct *task)
+{
+       if (!task)
+               return;  /* no thread running */
+       kthread_stop(task);
 }
 
 /**
@@ -683,7 +685,7 @@ static void visorhba_serverdown_complete(struct visorhba_devdata *devdata)
        /* Stop using the IOVM response queue (queue should be drained
         * by the end)
         */
-       kthread_stop(devdata->threadinfo.task);
+       visor_thread_stop(devdata->thread);
 
        /* Fail commands that weren't completed */
        spin_lock_irqsave(&devdata->privlock, flags);
@@ -1082,8 +1084,8 @@ static int visorhba_resume(struct visor_device *dev,
        if (devdata->serverdown && !devdata->serverchangingstate)
                devdata->serverchangingstate = true;
 
-       visor_thread_start(&devdata->threadinfo, process_incoming_rsps,
-                          devdata, "vhba_incming");
+       devdata->thread = visor_thread_start(process_incoming_rsps, devdata,
+                                            "vhba_incming");
 
        devdata->serverdown = false;
        devdata->serverchangingstate = false;
@@ -1159,8 +1161,8 @@ static int visorhba_probe(struct visor_device *dev)
                goto err_scsi_remove_host;
 
        devdata->thread_wait_ms = 2;
-       visor_thread_start(&devdata->threadinfo, process_incoming_rsps,
-                          devdata, "vhba_incoming");
+       devdata->thread = visor_thread_start(process_incoming_rsps, devdata,
+                                            "vhba_incoming");
 
        scsi_scan_host(scsihost);
 
@@ -1190,7 +1192,7 @@ static void visorhba_remove(struct visor_device *dev)
                return;
 
        scsihost = devdata->scsihost;
-       kthread_stop(devdata->threadinfo.task);
+       visor_thread_stop(devdata->thread);
        scsi_remove_host(scsihost);
        scsi_host_put(scsihost);