[SCSI] qla2xxx: Fix race that could hang kthread_stop()

There is a small race window in qla2x00_do_dpc() between
checking for kthread_should_stop() and going to sleep after
setting TASK_INTERRUPTIBLE. If qla2x00_free_device() is called
in this window, kthread_stop will wait forever because there
will be no one to wake up the process.

Fix by making sure we only set TASK_INTERRUPTIBLE before checking
kthread_stop().

Reported-by: Bandan Das <bandan.das@stratus.com>
Acked-by: Madhuranath Iyengar <Madhu.Iyengar@qlogic.com>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>

diff --git a/drivers/scsi/qla2xxx/qla_os.c b/drivers/scsi/qla2xxx/qla_os.c
index c194c23..15ce69e 100644 (file)
--- a/drivers/scsi/qla2xxx/qla_os.c
+++ b/drivers/scsi/qla2xxx/qla_os.c
@@ -3282,10 +3282,10 @@ qla2x00_do_dpc(void *data)
 
        set_user_nice(current, -20);
 
+       set_current_state(TASK_INTERRUPTIBLE);
        while (!kthread_should_stop()) {
                DEBUG3(printk("qla2x00: DPC handler sleeping\n"));
 
-               set_current_state(TASK_INTERRUPTIBLE);
                schedule();
                __set_current_state(TASK_RUNNING);
 
@@ -3454,7 +3454,9 @@ qla2x00_do_dpc(void *data)
                qla2x00_do_dpc_all_vps(base_vha);
 
                ha->dpc_active = 0;
+               set_current_state(TASK_INTERRUPTIBLE);
        } /* End of while(1) */
+       __set_current_state(TASK_RUNNING);
 
        DEBUG(printk("scsi(%ld): DPC handler exiting\n", base_vha->host_no));