Author: hselasky
Date: Wed Sep 11 08:20:13 2019
New Revision: 352206
URL: https://svnweb.freebsd.org/changeset/base/352206

Log:
  Fix synchronous work drain issue in the LinuxKPI.
  
  A work callback may restart itself. Loop in the drain function to see if the
  work has been rescheduled and stop the subsequent reschedules, if any.
  
  MFC after:            1 week
  Sponsored by:         Mellanox Technologies

Modified:
  head/sys/compat/linuxkpi/common/src/linux_work.c

Modified: head/sys/compat/linuxkpi/common/src/linux_work.c
==============================================================================
--- head/sys/compat/linuxkpi/common/src/linux_work.c    Wed Sep 11 07:53:49 
2019        (r352205)
+++ head/sys/compat/linuxkpi/common/src/linux_work.c    Wed Sep 11 08:20:13 
2019        (r352206)
@@ -1,5 +1,5 @@
 /*-
- * Copyright (c) 2017 Hans Petter Selasky
+ * Copyright (c) 2017-2019 Hans Petter Selasky
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -323,24 +323,26 @@ linux_cancel_work_sync(struct work_struct *work)
                [WORK_ST_CANCEL] = WORK_ST_IDLE,        /* cancel and drain */
        };
        struct taskqueue *tq;
+       bool retval = false;
 
        WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, NULL,
            "linux_cancel_work_sync() might sleep");
-
+retry:
        switch (linux_update_state(&work->state, states)) {
        case WORK_ST_IDLE:
        case WORK_ST_TIMER:
-               return (0);
+               return (retval);
        case WORK_ST_EXEC:
                tq = work->work_queue->taskqueue;
                if (taskqueue_cancel(tq, &work->work_task, NULL) != 0)
                        taskqueue_drain(tq, &work->work_task);
-               return (0);
+               goto retry;     /* work may have restarted itself */
        default:
                tq = work->work_queue->taskqueue;
                if (taskqueue_cancel(tq, &work->work_task, NULL) != 0)
                        taskqueue_drain(tq, &work->work_task);
-               return (1);
+               retval = true;
+               goto retry;
        }
 }
 
@@ -421,18 +423,19 @@ linux_cancel_delayed_work_sync(struct delayed_work *dw
                [WORK_ST_CANCEL] = WORK_ST_IDLE,        /* cancel and drain */
        };
        struct taskqueue *tq;
+       bool retval = false;
 
        WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, NULL,
            "linux_cancel_delayed_work_sync() might sleep");
-
+retry:
        switch (linux_update_state(&dwork->work.state, states)) {
        case WORK_ST_IDLE:
-               return (0);
+               return (retval);
        case WORK_ST_EXEC:
                tq = dwork->work.work_queue->taskqueue;
                if (taskqueue_cancel(tq, &dwork->work.work_task, NULL) != 0)
                        taskqueue_drain(tq, &dwork->work.work_task);
-               return (0);
+               goto retry;     /* work may have restarted itself */
        case WORK_ST_TIMER:
        case WORK_ST_CANCEL:
                if (linux_cancel_timer(dwork, 1)) {
@@ -442,14 +445,16 @@ linux_cancel_delayed_work_sync(struct delayed_work *dw
                         */
                        tq = dwork->work.work_queue->taskqueue;
                        taskqueue_drain(tq, &dwork->work.work_task);
-                       return (1);
+                       retval = true;
+                       goto retry;
                }
                /* FALLTHROUGH */
        default:
                tq = dwork->work.work_queue->taskqueue;
                if (taskqueue_cancel(tq, &dwork->work.work_task, NULL) != 0)
                        taskqueue_drain(tq, &dwork->work.work_task);
-               return (1);
+               retval = true;
+               goto retry;
        }
 }
 
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