[S390] cio: prevent workqueue deadlock

Subchannel reprobing can block the kslowcrw workqueue indefinitely
while waiting for device recognition to finish which is also scheduled
to run on kslowcrw. Prevent this deadlock by moving the waiting
portion of subchannel reprobing to the cio workqueue.

Signed-off-by: Peter Oberparleiter <peter.oberparleiter@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

diff --git a/drivers/s390/cio/css.c b/drivers/s390/cio/css.c
index 1f2e424596af282b4937fd93fa30407930d5f2b4..8446d15e4485dcdff69b52fa536af77a91768f3c 100644 (file)
--- a/drivers/s390/cio/css.c
+++ b/drivers/s390/cio/css.c
@@ -533,6 +533,17 @@ static int reprobe_subchannel(struct subchannel_id schid, void *data)
        return ret;
 }
 
+static void reprobe_after_idle(struct work_struct *unused)
+{
+       /* Make sure initial subchannel scan is done. */
+       wait_event(ccw_device_init_wq,
+                  atomic_read(&ccw_device_init_count) == 0);
+       if (need_reprobe)
+               css_schedule_reprobe();
+}
+
+static DECLARE_WORK(reprobe_idle_work, reprobe_after_idle);
+
 /* Work function used to reprobe all unregistered subchannels. */
 static void reprobe_all(struct work_struct *unused)
 {
@@ -540,10 +551,12 @@ static void reprobe_all(struct work_struct *unused)
 
        CIO_MSG_EVENT(4, "reprobe start\n");
 
-       need_reprobe = 0;
        /* Make sure initial subchannel scan is done. */
-       wait_event(ccw_device_init_wq,
-                  atomic_read(&ccw_device_init_count) == 0);
+       if (atomic_read(&ccw_device_init_count) != 0) {
+               queue_work(ccw_device_work, &reprobe_idle_work);
+               return;
+       }
+       need_reprobe = 0;
        ret = for_each_subchannel_staged(NULL, reprobe_subchannel, NULL);
 
        CIO_MSG_EVENT(4, "reprobe done (rc=%d, need_reprobe=%d)\n", ret,